SAN-b-P4VP Block Copolymer Synthesis by Chain Extension from RAFT-Functional Poly(4-vinylpyridine) in Solution and in Emulsion

ArticleinMacromolecules 40(20) · September 2007with 143 Reads
Abstract
Reversible addition fragmentation chain transfer (RAFT)-mediated polymerization was successfully applied for the synthesis of poly(4-vinylpyridine) (P4VP) polymers of predetermined molar mass and of low polydispersity index. These RAFT end-functionalized polymers were then used as macro-RAFT agents and further chain extended with an azeotropic mixture of styrene (STY) and acrylonitrile (AN) (63 mol % STY). Initially, these chain extension experiments were carried out in solution. In that case, the formation of the P4VP-b-SAN block copolymers clearly demonstrated the large fraction of chain end functionality in these RAFT-functional P4VP polymers. Proof of the formation of low molar mass P4VP-b-SAN block copolymer was obtained by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Gradient polymer elution chromatographic (GPEC) analysis confirmed successful formation of P4VP-b-SAN block copolymers. Block copolymer synthesis in emulsion was also investigated. The polymerization mediated by a RAFT-functional P4VP, macro-RAFT agent, was carried out as a semicontinuous process. The complete transformation of the P4VP starting block into P4VP-b-SAN block copolymer points to an efficient control of the polymerization in emulsion. This procedure leads to the formation of a colloidally stable latex. The results of GPEC analysis confirmed the successful block copolymer latex formation.

Do you want to read the rest of this article?

Request full-text
Request Full-text Paper PDF
  • ... The PAA macro-RAFT agent is a living polymer which contains a hydrophilic PAA segment and trithiocarbonate end group [32]. The PAA macro-RAFT agent can be further chain-extended with hexafluorobutyl acrylate (HFBA) in water to form amphiphilic block copolymers able to selfassemble into micelles in which the polymerization continues, as shown in Scheme 2. This approach has evolved as a simple way of producing amphiphilic block copolymer particles by polymerizationinduced self-assembly (PISA) performed in water [33][34][35][36][37][38][39][40][41][42][43][44][45]. The aqueous RAFT-mediated emulsion polymerization performed with polyacid-based marco- RAFT agents has been reported to be very sensitive to the pH of the reaction medium [46][47][48][49]. ...
    ... The PAA macro-RAFT agent is a living polymer which contains a hydrophilic PAA segment and trithiocarbonate end group [32]. The PAA macro-RAFT agent can be further chain-extended with hexafluorobutyl acrylate (HFBA) in water to form amphiphilic block copolymers able to self-assemble into micelles in which the polymerization continues, as shown in Scheme 2. This approach has evolved as a simple way of producing amphiphilic block copolymer particles by polymerization-induced self-assembly (PISA) performed in water [33][34][35][36][37][38][39][40][41][42][43][44][45]. The aqueous RAFT-mediated emulsion polymerization performed with polyacid-based marco-RAFT agents has been reported to be very sensitive to the pH of the reaction medium [46][47][48][49]. ...
    Article
    Full-text available
    This paper describes a very simple strategy towards self-stabilized poly(acrylic acid)-block-poly(hexafluorobutyl acrylate) (PAA-b-PHFBA) block copolymer particles via reversible addition-fragmentation chain transfer (RAFT)-mediated polymerization-induced self-assembly. Hexafluorobutyl acrylate (HFBA) monomer conversion and number-average molar mass of PAA-b-PHFBA increased gradually with the increase in the pH value of the aqueous phase. When pH < 10, the molecular weight distributions of PAA-b-PHFBA were narrow, however, when the pH was raised to 11.55, PAA-b-PHFBA block copolymers had a broader distribution (DM = 1.82) with a serious trailing toward the low molecular weight. Furthermore, the morphology and size of PAA-b-PHFBA latex particles were measured by transmission electron microscopy and dynamic light scattering. The results indicated that the PAA-b-PHFBA latex particles had a clear spherical core-shell structure and the latex particles' size increased with the increase of pH value.
  • ... Another variant, in which block copolymers form structured dispersions of particles during the synthe- sis, is implemented under conditions of emulsifier- free emulsion polymerization. In this case, a poly- meric precursor is used, which is usually a hydrophilic polymer that stabilizes the formed polymer-monomer particles (functions as a surfactant) and initiates for- mation of a block copolymer in the polymerization of a hydrophobic monomer (which is a polymeric RAFT agent) [179][180][181][182][183][184][185][186][187][188][189][190]. Asymmetric trithiocarbonates R- SC(=S)S-R' are more often used as RAFT agents, and during the synthesis hydrophilic precursor A n - SC(=S)S-R' (poly(ethylene oxide), PMAA, and its copolymers with hydrophilic comonomers, PAA, poly(styrenesulfonic acid) or its sodium salt, etc.) is initially formed and then amphiphilic diblock copoly- mer A n -B m -SC(=S)S-R' is afforded [182][183][184][185][186][187]. ...
    ... In this case, a poly- meric precursor is used, which is usually a hydrophilic polymer that stabilizes the formed polymer-monomer particles (functions as a surfactant) and initiates for- mation of a block copolymer in the polymerization of a hydrophobic monomer (which is a polymeric RAFT agent) [179][180][181][182][183][184][185][186][187][188][189][190]. Asymmetric trithiocarbonates R- SC(=S)S-R' are more often used as RAFT agents, and during the synthesis hydrophilic precursor A n - SC(=S)S-R' (poly(ethylene oxide), PMAA, and its copolymers with hydrophilic comonomers, PAA, poly(styrenesulfonic acid) or its sodium salt, etc.) is initially formed and then amphiphilic diblock copoly- mer A n -B m -SC(=S)S-R' is afforded [182][183][184][185][186][187]. Symmetric trithiocarbonates R-SC(=S)S-R, which allow the two-stage synthesis of amphiphilic triblock copolymers A n -B m -SC(=S)S-B m -A n , were hardly applied for the synthesis of amphiphilic block copoly- mers via emulsion polymerization. ...
    Article
    Full-text available
    Modern approaches to the synthesis of tailor-made macromolecules by radical polymerization proceeding through the reversible addition-fragmentation chain-transfer mechanism are considered. The mechanism of this process and the experimental and calculation methods for determining its main kinetic parameters are discussed. Particular emphasis is placed on the problems of designing copolymers of various microstructures, including random, gradient, and block copolymers.
  • ... For this purpose, all versions of polymerization with reversible chain deactivation may be used [1,[8][9][10][11][12][13][14][15][16]. Reversible addition-fragmentation chain transfer (RAFT) polymerization is most frequently used [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], which is related to the tolerance of the above mechanism to functional groups of the monomer, the wide variety of suitable solvents, and mild polymerization conditions. The most widespread RAFT agents are asymmetric trithiocarbonates of the general structure R-SC(=S)S-R', where R is a unique "outgoing" group (i.e., the group reinitiating polymerization) [30]. ...
    Article
    Full-text available
    The effect of the chain length of oligomer acrylic acid obtained in the presence of a low-molecular-mass trithiocarbonate and the position of trithiocarbonate fragment (within the chain or at the chain end) on the process of emulsion polymerization of n-butyl acrylate and characteristics of the resulting dispersions has been studied for the first time. It has been found that, when using an oligomer with trithiocarbonate group located within the chain in the emulsion polymerization of n-butyl acrylate in a wide range of monomer– water phase compositions, triblock copolymers self-organizing in aqueous medium to give stable particles with the core–shell structure are formed. Oligomers with M n ~ (5–10) × 10 3 are optimal for synthesis of stable dispersions. In this case, block copolymers with the controlled length of hydrophobic block and a rather narrow MWD may be obtained. Thin films formed from these copolymers retain the structure of the initial dispersions on solvent removal. If the trithiocarbonate group in the oligomer is located at the chain end, the main polymerization product is a diblock copolymer. In this case, the formation of polymer–monomer particles occurs during a longer period of time, the control of MWD is weakened, and the dispersions of particles lose the aggregative stability after thin film formation.
  • ... regardless of the implemented technique. Beside their insolubility in tetrahydrofuran, which has long restricted the use of size exclusion chromatography (SEC) for their characterization, the major issue with P4VP is their strong adsorption onto chromatographic stationary phases [15] [16] [17] [18]. This deleterious effect was systematically observed for oligomers with more than 20 units, even when using a good solvent such as N,N-dimethylformamide (DMF), and this was assigned to the higher nitrogen accessibility of P4VP as compared to their P2VP homologues for which such SEC methods were found to be efficient [15]. ...
    Article
    The position of nitrogen atoms in poly(4-vinylpyridine) (P4VP), compared to their poly(2-vinylpyridine) (P2VP) isomers, explains most difficulties faced when determining their molecular weight parameters by size exclusion chromatography, due to oligomers strongly adsorbing onto stationary phases. The high accessibility of these nitrogen atoms is shown here to be challenging also in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), probably accounting for the lack of mass data reported for P4VP in the literature. Using a “bottom-up” strategy starting from small oligomers prior to consider high molecular weight polymers, P4VP species were observed here to strongly interact with acidic matrix molecules such as 2,5-DHB when preparing MALDI sample using the traditional dried-droplet procedure. In contrast, MALDI best performed when using a solvent-free sample preparation involving a non-acidic matrix such as DCTB. Accordingly, reliable MS determination of molecular weight parameters could be achieved for P4VP up to about 40 kDa, as validated by diffusion NMR experiments.
  • Article
    SCOPE The aim of this review is to give a compact overview about the literature on mass spectrometry (MS) of polymers published during 2006/2007. The citations are drawn from SciFinder January 25, 2008, using the search terms "poly*" and "mass spectrometry" with restrictions to review and journal contributions in the English language including refined searches in Web of Science. More than 750 relevant papers, reviews, (1, 2) and historical summaries (3, 4) were published in these two years, demonstrating the importance of MS for polymer analysis. We were therefore forced to select the most important references. This is always a subjective decision and may not always represent the best choices. In contrast to the previous review in this series (5), which focused on MS principles, including matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF), electrospray ionization (ESI) TOF, TOF secondary ion mass spectrometry (SIMS), etc., in this paper, we categorize according to applications of MS for polymer analysis. Even this choice is arbitrary. The main chapters are focused on New Techniques and Principles, Polymer Synthesis, Copolymer Analysis, Fragmenta-tion Techniques, Polymer Degradation, and Polymer Surface and Interface. Due to their comprehensiveness and complexity, clear classification of some papers to a single category is difficult. Thus, Copolymer Analysis exclusively deals with the determination of the copolymer composition, whereas the synthesis of copolymers is described in Polymer Synthesis. Sometimes, making a clear decision between synthetic poly-mers and biopolymers, because both fields strongly overlap, is difficult. Typical examples for this overlap are papers of Boyer et al. (6) on the synthesis of well-defined protein-polymer conjugates via in situ reversible addition-fragmentation chain-transfer (RAFT) polymerization and also poly(ether-urethane) biobased sugar diols by Beldi et al. (7).
  • Article
    Over the last two decades the evaporative light scattering detector (ELSD) has found more and more use in liquid chromatography (LC) of synthetic polymers. The reason behind this is that it can be used for a significantly wider variety of analyte/solvent combinations. Although in many of the applications the ELSD has been used in a qualitative manner, it can also be used quantitatively. For quantitative interpretation of analyses it is, in the case of synthetic polymers, essential to know how parameters, which characterize a polymer sample (i.e., molar mass and chemical composition), as well as parameters, which are a consequence of the LC separation (i.e., composition and flow rate of the mobile phase, its composition), influence the response of the ELSD. This review gives a tabulated overview over applications of ELS detectors in polymer analysis. The influence of parameters arising from either the polymer side or the chromatographic separation is discussed in detail and, in addition, the influence of the ELS detector's running conditions, i.e. type and flow rate of gas and temperature of nebulizer and evaporator), will be reviewed. This information will prove valuable whenever the calibration of an ELSD for the quantitative analysis of synthetic polymers is attempted.
  • Article
    Poly(ethylene oxide) (PEO) based macroRAFT agents with various chemical structures have been used as both stabilizer and control agent for the polymerization of styrene in miniemulsion conditions. Trithiocarbonate (PEO-DTTC (Z = thiododecyl), PEO-PTTC (Z = thiopropyl)) functional groups were attached to a commercial monomethyl ether PEO (Mn = 2000 g mol−1). PEO-DTTC and PEO-PTTC allowed the formation of stable miniemulsions of styrene in water. Our previous results (A. M. Dos Santos, T. Le Bris, C. Graillat, F. D'Agosto, M. Lansalot, Macromolecules, 2009, 42, 946) showed that PEO-based dithiobenzoate (PEO-DB) led to controlled polymerization but also to broad molar mass distribution (PDI = 1.9) and multipopulated polymer chains. The switch from PEO-DB to PEO-DTTC greatly improved the molar mass distribution (PDI = 1.6). This was ascribed to the ability of PEO-DTTC to be localized at the water/monomer droplets interface. An increase in PEO-DTTC concentration improved the control of the polymerization. However, the concomitant formation of micelles favored secondary nucleation. This was attenuated by the use of PEO-PTTC, less prone to form micelles in water which greatly improved both the quality of control (PDI = 1.3) and the particle size distribution and showed that the particles were constituted of well-defined PEO-b-PS polymer chains. These results could be attributed to a more efficient anchoring of PEO-PTTC at the monomer droplet or particle/water interface showing the crucial role of the macroRAFT structure in these systems.
  • Article
    Two novel reversible addition–fragmentation chain transfer (RAFT) reagents bearing functional groups, S,S′-bis(9-anthrylmethyl) trithiocarbonate (BATTC) and S,S′-bis(1-naphthylmethyl) trithiocarbonate (BNTTC) were synthesized and used for the RAFT polymerizations of styrene (St). The polymerization results showed that the RAFT polymerizations could be well controlled using BNTTC or BATTC as the RAFT agents. For example, the polymerization rates were of first-order with respect to the monomer concentration, and the molecular weights of the obtained polystyrenes (PS) with narrow molecular weight distributions increased linearly with the monomer conversions and were close to their theoretical values in the presence of BNTTC or BATTC. The successful reaction of chain extension and analysis of 1H NMR spectra confirmed the existence of the functional anthracene or naphthalene groups at the chain end of the correspondingly obtained PS. Optical properties of the obtained PS were characterized by fluorescence and UV absorption. Photochemical properties of the obtained PS end capped with anthracene were also described under irradiation of UV light.
  • Article
    Full-text available
    This paper provides a second update to the review of reversible deactivation radical polymerization achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible additionfragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379410). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669692). This review cites over 500 papers that appeared during the period mid-2006 to mid-2009 covering various aspects of RAFT polymerization ranging from reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses and a diverse range of applications. Significant developments have occurred, particularly in the areas of novel RAFT agents, techniques for end-group removal and transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.
  • Article
    A hydrophilic poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) copolymer with a trithiocarbonate reactive group was used in the free-radical, batch emulsion polymerization of styrene. It allowed fast polymerizations and high final conversions to be achieved, and the parameters for a good control over the formation of well-defined amphiphilic diblock copolymers were identified. These diblock copolymers self-assembled in situ into nano-objects of various morphologies upon chain extension. Achieving a good control over the formed diblock copolymers was shown to be an important step toward a better understanding of the parameters that affect the shape and size of the self-assembled objects, the ultimate goal being the ability to predict and fine-tune them on purpose.
  • Article
    Styrene (S)/acrylonitrile [AN; initial acrylonitrile molar feed compositions (f AN,0's) = 0.10-0.86) and tert-butyl methacrylate (tBMA)/AN (f AN,0 = 0.10-0.80) copolymers were synthesized at 90°C in 50 wt % 1,4-dioxane solutions with a unimolecular initiator, N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop- 2-yl) hydroxylamine [BlocBuilder (BB)]. In the tBMA/AN copolymerizations, 8.0-8.5 mol % N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) free nitroxide relative to BB was added. The S/AN copolymers exhibited narrow, monomodal molecular weight distributions (MWDs) with low polydispersities [weight-average molecular weight (M w)/number-average molecular weight (M n) = 1.14-1.26], and the M n versus monomer conversion (X) plots were relatively linear (M n = 18.1 kg/mol, X ≈ 0.7); this suggested that pseudo-living behavior was approached. AN proved to be an effective controlling comonomer for tBMA because the tBMA/AN copolymers exhibited narrow monomodal MWDs with M w/M n = 1.17-1.50 and relatively linear M n versus X plots to reasonably high X values (M n = 15.6 kg/mol, X ≈ 0.6). The AN and S monomer reactivity ratios were r AN = 0.07 ± 0.01 and r S = 0.27 ± 0.02 (Fineman-Ross) and r AN = 0.10 ± 0.01 and r S = 0.28 ± 0.02 (Kelen-Tüdos), respectively; these values were in good agreement with conventional free-radical polymerization. Error-in-variables model (EVM) analysis indicated that the use of cumulative composition S/AN data was more effective than typical approaches using low-X data with the Mayo-Lewis model. The AN and tBMA reactivity ratios [r AN = 0.07 ± 0.01 and r tBMA = 1.24 ± 0.20 (Fineman-Ross) and r AN = 0.14 ± 0.01 and r tBMA = 0.89 ± 0.19 (Kelen-Tüdos)] were similar to those reported for related alkyl methacrylate/AN conventional radical copolymerizations. EVM analysis suggested significant experimental error was associated with the tBMA/AN system, and this warrants further investigation.
  • Article
    Acrylonitrile‐styrene‐acrylate (ASA) toughened plastics based on block copolymers are successfully prepared via RAFT emulsion polymerization and various molecular structures are designed to have different morphologies in order to investigate the relationship between morphologies and mechanical properties. All materials prepared by blending exhibit sea‐island morphology. Promoting particles dispersion and increasing spherical particle size shorten surface‐to‐surface interparticle distance and help to improve tensile properties of materials. Enlarging particles through crosslinked structures are found to be a more effective method to improve tensile toughness, at the cost of a slight reduction in tensile yield strength. Larger spherical particles with crosslinked structures are found to help improving the Izod notched impact strength of materials. However, the existence of a SAN core decreases the material's ability to withstand impact. Compared to blended samples, triblock copolymer materials display higher flexural strength with equal flexural modulus. Acrylonitrile‐styrene‐acrylate (ASA) toughened plastics based on block copolymers are successfully prepared via RAFT emulsion polymerization. And the effect of molecular structures of block copolymers on the morphology and mechanical properties of ASA are investigated in this paper. The results show that ASAs own different mechanical properties with various morphologies, which depend on the molecular structures of block copolymers.
  • Article
    The RAFT-mediated, surfactant-free, ab initio, batch emulsion polymerization of n-butyl acrylate (nBA) and its copolymerization with methyl methacrylate (MMA) were studied. The control agent was a surface-active trithiocarbonate macromolecular RAFT agent composed of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic dodecyl chain. The homopolymerizations of nBA were fast with high final conversions, and the polymer chains were well-controlled with narrow molar mass distribution. The length of the PEO chain was shown to affect the particle size and the polymerization kinetics directly. We found the conditions to tune the particle size independently from the poly(n-butyl acrylate) chain length by playing with a mixture of macro-RAFT agents with long and short PEO segment or by adding a PEO-based nonionic surfactant. The copolymerizations of nBA and MMA exhibited features very similar to those of the nBA homopolymerizations provided that the molar percentage of MMA did not exceed approximately 75%. In all cases, stable, submicrometric particles composed of amphiphilic diblock copolymer chains were formed.
  • Poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride] trithiocarbonate, which contains the reactive trithiocarbonate group and the appending surface-active groups, is used as both surfactant and macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agent in batch emulsion polymerization of styrene. Under the conditions at high monomer content of ∼20 wt % and with the molecular weight of the macro-RAFT agent ranging from 4.0 to 15.0 kg/mol, well-controlled batch emulsion RAFT polymerization initiated by the hydrophilic 2-2′-azobis(2-methylpropionamidine) dihydrochloride is achieved. The polymerization leads to formation of nano-sized colloids of the poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride]-b- polystyrene-b-poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride] triblock copolymer. The colloids generally have core-shell structure, in which the hydrophilic block forms the shell and the hydrophobic block forms the core. The molecular weight of the triblock copolymer linearly increases with increase in the monomer conversion, and the values are well-consistent with the theoretical ones. The molecular weight polydispersity index of the triblock copolymer is below 1.2 at most cases of polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
  • Article
    The purpose of this paper was to study the application of a surface-active trithiocarbonate RAFT agent, the 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, sodium salt (TTCA) in surfactant-free, ab initio, batch emulsion polymerization. Because of the highly water-soluble character of the leaving group favoring exit from the micelles or the particles over reinitiation, the polymerization of styrene was completely inhibited. In contrast, the polymerization of n-butyl methacrylate was fast and led to small, stable particles, demonstrating the good stabilizing efficiency of TTCA. However, the control over molar mass was not effective, as homopolymers with high molar mass were formed. This was related to the inappropriate leaving/initiating group and low chain transfer constant of the RAFT agent in the free-radical polymerization of methacrylic esters and was also observed in bulk. This poor efficiency was overcome by copolymerizing n-butyl methacrylate with a low percentage of styrene or n-butyl acrylate. In this case, the bulk copolymerization led to controlled copolymers with predicted molar mass and narrow molar mass distribution and the chain transfer efficiency was similarly high in surfactant-free emulsion polymerization. The good colloidal characteristics of the latexes with the stabilizing group attached at the chain-end were maintained, leading to autostabilized latexes with small particle diameter, below 150 nm. This work is the first example of the direct and efficient use of a surface-active, low molar mass, RAFT agent in emulsifier-free, batch emulsion polymerization, leading simultaneously to a good control over molar mass and narrow molar mass distribution, together with good colloidal properties.
  • Article
    A synthesis approach to achieve stable latex particles composed of polymer chains with controlled molar mass and narrow molar mass distribution has been presented. The approach uses a simple poly(ethylene oxide (PEO)-based amphiphilic RAFT agent (PEO-TTC) as both the stabilizer and the control agent in ab initio batch emulsion polymerization of styrene and n-butyl acrylate. In a emulsion polymerization, the PEO-TTC and the initiator were solubilized in deionized water containing NaHCO3, followed by the addition of monomer, styrene or n-butyl acrylate, under stirring. After deoxygenation by nitrogen bubbling, the flask was immersed in an oil bath thermostated at 70°. Recovered polymers exhibited the macromolecular characteristics expected in controlled radical polymerization, such as low polydispersity indices. The approach, with a minimum of components and in the absence of free surfactant, allows easy formation of autostabilized latexes composed of diblock polymers.
  • Article
    The RAFT-mediated emulsion polymerization of styrene was carried out in a one-pot, two-step procedure using two poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) macroRAFT agents of different compositions carrying a reactive trithiocarbonate end-group. The latter were prepared in situ, directly in aqueous solution at acid pH. In all cases, the synthesis was fast and efficient, leading to very high conversions and very good control over the polymer features. It was moreover particularly reproducible, which is an important outcome for the robustness of the method. Then, styrene was added and directly polymerized in the formed emulsion system until very high conversion in short reaction time. The method led to amphiphilic block copolymers, self-assembled into stable spherical particles. The diameter of the latter was directly governed by the initial concentration of macroRAFT agent, which also controlled the molar mass of the polystyrene block at constant styrene initial concentration. The emulsion polymerization step was studied in detail to provide information on the overall mechanism: nucleation, conversion rate, and chain growth. Because of the reduction of the number of synthesis and purification steps and of the overall reaction time, and due to the use of water as the sole reaction medium, the proposed method is of high interest in terms of both respect of environmental constraints and energy saving.
  • Article
    The SG1-mediated copolymerization of methacrylic acid and a small percentage of sodium 4-styrenesulfonate was performed in water solution at 76 °C, using BlocBuilder as an alkoxyamine initiator under acidic conditions. Unexpectedly, these conditions, which could be considered as rather unfavorable due to the instability of SG1 in acidic water, led to very good results in term of polymerization kinetics and control over polymer chain growth. It appeared that low temperature and short reaction time were the key parameters to maintain a good living character to the chains as evaluated by in situ 31P NMR. The aqueous system was then used directly as the polymerization medium for the emulsion copolymerization of methyl methacrylate and styrene performed at 90 °C. This one-pot procedure led to the synthesis of amphiphilic block copolymers that self-assembled into stable core–shell nanoparticles.
  • Article
    Water-soluble poly(N,N-dimethylacrylamide)s (PDMAAm) with a reactive trithiocarbonate group exhibiting different structures were used as macromolecular RAFT (reversible addition−fragmentation chain transfer) agents in the surfactant-free emulsion polymerization of n-butyl acrylate and styrene, under ab initio, batch conditions. Independently of the structure of the RAFT group, the polymerizations were fast and controlled with molar masses that matched well the theoretical values and rather low polydispersity indexes. Monomer conversions close to 100% were reached and the polymerizations behaved as controlled systems, even when solids contents up to 40% were targeted. The system thus led to poly(N,N-dimethylacrylamide)-b-poly(n-butyl acrylate) and poly(N,N-dimethylacrylamide)-b-polystyrene amphiphilic diblock copolymers formed in situ and self-assembled upon chain extension. The stability of the aqueous dispersions, measured by the amount of coagulum formed, improved with increasing length of the stabilizing hydrophilic PDMAAm segments.
  • Aqueous emulsion polymerizations of styrene were performed in the presence of a macromolecular reversible addition-fragmentation chain transfer (RAFT) agent (macroRAFT) composed of acrylic acid (AA) and poly(ethylene oxide) methyl ether acrylate (PEOA), end-capped by a reactive dodecyl trithiocarbonate group (P(AA-co-PEOA)-TTC). The influence of the stirring speed or the presence of different amounts of a divalent salt, CaCl2, were investigated in this polymerization-induced self-assembly process, in which spherical and nonspherical nano-objects were formed upon the synthesis of amphiphilic diblock copolymers in situ. It appeared that the addition of CaCl2 led to the controlled formation of different nano-objects such as spheres, fibers or vesicles, whereas an appropriate stirring speed was required for the formation of nanofibers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
  • Effective ways to conduct controlled/living radical polymerization (CRP) in emulsion systems are necessary for commercial latex production without significant modification of current industrial facilities. Conducting CRP in emulsion media is more complicated and more challenging than its application in homogeneous bulk. These challenges come from the intrinsic kinetics of emulsion polymerization. They include mass transport, slow chain growth mechanism, and exit of short radicals from polymeric particles. This review describes the recent developments of CRP in heterogeneous dispersion, including miniemulsion, microemulsion, dispersion, and especially emulsion. Various approaches for conducting emulsion CRP are detailed, including controlled seeded emulsion polymerization, nanoprecipitation, use of short oligomers as macroinitiators for in situ block copolymerization, and RAFT-mediated self-assembly. In addition many remaining challenges of the current methods barring wide spread industrial application of emulsion CRP are also suggested. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6983–7001, 2008
  • Article
    The structured nanoparticles of styrene (St) and butadiene (Bd) block copolymers were prepared by RAFT seeded emulsion polymerization of butadiene. It was confirmed that the block copolymers of PSt-b-P(St-co-Bd) was formed with controlled molecular weight and rather low PDI at low composition of the P(St-co-Bd) segment. With more incorporation of butadiene, the branching reaction of polybutadiene became obvious, leading to higher PDI and positive deviation of Mn from the theoretical predication. At the gel point, the composition of the P(St-co-Bd) segment was estimated to be 0.72. After this, the gel fraction increased quickly. The morphology of structured nanoparticles could be largely tuned simply by the copolymer composition. With the composition of the P(St-co-Bd) segment increased from 0.37 to 0.92, the morphology within the structured particles changed from the polybutadiene domains-in-polystyrene matrix, perforated concentric-spherical layer, concentric-spherical multi-layers, bi-continuous, to broken layers of polystyrene in polybutadiene matrix. It was found that the morphology of the block copolymer within nanoparticles was dependent on d/L values, which was in excellent agreement with the theoretical prediction.Graphical abstract
  • Chapter
    The synthesis of hybrid and core–shell nanoparticles using controlled/ living radical polymerization in aqueous dispersed systems is reviewed. The processes involve emulsion, miniemulsion, and dispersion polymerizations as well as grafting techniques, with the aim of producing submicrometric latex particles with well-defined morphologies that might not be accessible via classical radical polymerization. Those morphologies include organic/inorganic hybrids, nanostructured particles, (nano)capsules, and particles with a hydrophobic core and hydrophilic shell. Controlled/living radical polymerization-Core–shell particle-Dispersion polymerization-Emulsion polymerization-Grafting from-Hybrid-Miniemulsion polymerization-Nanogel-Nanoparticle
  • Article
    A poly(ethylene oxide)-based macromolecular agent for reversible addition-fragmentation chain transfer (PEO-RAFT, 2 000 g·mol−1) was synthesized and used as a stabilizer and a control agent in the miniemulsion polymerization of styrene. Using 2,2′-azobis(isobutyronitrile) as initiator, stable polystyrene (PS) particles sterically stabilized by the PEO segments were obtained with almost complete conversion after 22 h. Molar masses increased linearly with conversion although rather broad molar mass distributions were obtained due to the presence of several populations of PEO-b-PS block copolymers. However, dynamic light scattering analyses showed a significant increase in particle diameter with conversion and the ratio of the number of particles to the number of droplets (Np/Nd) was thus lower than one indicating that the system did not follow a true miniemulsion process. Transmission electron microscopy additionally revealed the presence of holes inside the formed particles suggesting that block copolymer PEO-b-PS could be buried inside the particles during the polymerization. Varying the concentration and the nature of the initiator did not lead to an improvement of the molar mass distribution, while a decrease in polymerization temperature to 40 °C enabled to keep the particle size constant throughout the polymerization with values close to the starting droplet diameter as expected for a true miniemulsion.
  • Article
    This Perspective describes the recent developments of polymerization-induced self-assembly of amphiphilic block copolymers based on controlled/living free-radical polymerization (CRP) in water. This method relies on the use of a hydrophilic living polymer precursor prepared via CRP that is extended with a hydrophobic second block in an aqueous environment. The process thus leads to amphiphilic block copolymers that self-assemble in situ into self-stabilized nano-objects in the frame of an emulsion or dispersion polymerization process. Depending on the nature and the structure of the so-formed copolymer, not only spherical particles can be achieved but also all morphologies that can be found in the phase diagram of an amphiphilic block copolymer in a selective solvent. This paper focuses mainly on aqueous emulsion or dispersion polymerization and gives an overview of the CRP techniques used, the general conditions, and the morphologies obtained.
  • Article
    The emulsion polymerization of styrene in the presence of hydrophilic poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate), P(MAA-co-PEOMA), macromolecular RAFT (reversible addition–fragmentation chain transfer) agents possessing a trithiocarbonate reactive group and 19 ethylene oxide subunits in the grafts was performed to create in situ P(MAA-co-PEOMA)-b-polystyrene amphiphilic block copolymer self-assemblies. The system was studied using the following conditions: a pH of 5, two different compositions of the MAA/PEOMA units (50/50 and 67/33, mol/mol), different molar masses of the macroRAFT agents, and various concentrations of the latter targeting different molar masses for the polystyrene block. This work completes a previous one performed at pH 3.5, under otherwise similar experimental conditions, for which only spherical particles were obtained [Zhang et al. Macromolecules2011, 44, 7584]. For both MAA/PEOMA compositions, the system led to different nano-object morphologies such as spherical micelles, nanofibers, and vesicles, depending directly on the molar masses of the hydrophilic and hydrophobic blocks. A pH of 5 was shown to be the best compromise to achieve nonspherical particles while keeping a good control over the chain growth.
  • Article
    An update to the comprehensive review on controlled/living radical polymerization (CLRP) is discussed. The two most well-known CLRP systems that operate based on the persistent radical effect (PRE) are NMP and ATRP, and both have been studied extensively with regard to compartmentalization. xanthates are suitable as RAFT agents for implementation of ab initio RAFT emulsion polymerization due to their low reactivity. Xu and colleagues employed RAFT miniemulsion polymerization to prepare cross-linked chiral nanoparticles comprising well-defined glycopolymers by use of the chiral monomer 6-O-p-vinylbenzyl-1,2:3,4-di-O-isopropylidene-D-galactopyranose (VBPG) and poly-(VBPG) as the macro-RAFT agent. Emulsion ATRP has been conducted in aqueous dispersed systems as ab initio emulsion polymerization using direct and reverse ATRP, as well as in seeded emulsion systems using both direct ATRP and AGET ATRP. One of the most significant steps forward in recent years is the realization that emulsion/dispersion CLRP systems can be effectively employed to prepare polymeric nano-objects of nonspherical morphologies, such as rods and vesicles; this is currently one of the most active areas in this field.
  • Article
    Binary polystyrene and poly(4-vinylpyridine) mixed grafted silica nanoparticles (PSt/P4VP-g-SNPs) are fabricated using CuI-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) via grafting-to method. Azide-terminated PSt and P4VP are synthesized via post- and pre-atom transfer radical polymerization modification, respectively. Then, the polymers are simultaneously anchored onto alkyne-modified SNPs by CuAAC yielding mixed brushes as shown by Raman spectroscopy, dynamic light scattering, and thermogravimetric analysis. To the best of our knowledge, this is the first report of simultaneously grafting two distinct polymer chains to synthesize mixed grafted silica nanoparticles using CuAAC technique via grafting-to method.
  • Chapter
    This chapter discusses the recent work involving the polymerization-induced self-assembly (PISA) process performed in water and water-based systems using different controlled polymerization techniques. Since the 1990's, with the development of controlled radical polymerization (CRP) techniques, the advances in polymer chemistry have accelerated in combining the desirable features of living polymerization techniques already known mainly from ionic polymerizations with the simplicity of a free radical process. Free-radical polymerization is the most important method for the production of synthetic polymers in large-scale industrial production and in the manifold applications. Nitroxide-mediated polymerization and atom transfer radical polymerization represent the two most commonly used methods of CRP based on a reversible termination reaction. Atom-transfer radical polymerization (ATRP) is based on the reversible transfer of a halogen atom between a dormant alkyl halide and a transition metal catalyst in a redox reaction.
  • Article
    Nanostructured soft materials open up new opportunities in material design and application, and block copolymer self-assembly is one particularly powerful phenomenon that can be exploited for their synthesis. The advent of controlled/living radical polymerisation (CLRP) has greatly simplified block copolymer synthesis, and versatility towards monomer types and polymer architectures across the different forms of CLRP has vastly expanded the range of functional materials accessible. CLRP-controlled synthesis of block copolymers has been applied in heterogeneous systems, motivated by the numerous process advantages and the position of emulsion polymerisation at the forefront of industrial latex synthesis. In addition to the inherent environmental advantages of heterogeneous routes, the incidence of block copolymer self-assembly within dispersed particles during polymerisation leads to novel nanostructured materials that offer enticing prospects for entirely new applications of block copolymers. Here, we review the range of block copolymers prepared by heterogeneous CLRP techniques, evaluate the methods applied to maximise purity of the products, and summarise the unique nanoscale morphologies resulting from in situ self-assembly, before discussing future opportunities within the field.
  • Article
    Regularities of the formation of acrylonitrile-acrylamide copolymers obtained from initial monomer feeds containing 1–50 wt % acrylamide in DMSO solutions with the participation of low-molecular-mass and polymeric trithiocarbonates as reversible addition-fragmentation chain transfer agents are studied for the first time. It is shown that the copolymerization in the presence of low-molecular-mass trithiocarbonates proceeds via a pseudo-living mechanism. The synthesized copolymers prove to be inefficient as reversible addition-fragmentation chain transfer agents, a result that leads to products with bimodal molecular-mass distributions. The rheological characteristics of solutions, as well as the thermal behavior of the copolymers obtained in the absence and in the presence of reversible addition-fragmentation chain transfer agents, are studied. The effect of the synthesis conditions on the properties of the synthesized copolymers is discussed.
  • Article
    The pseudoliving radical binary copolymerization of acrylonitrile with methyl acrylate, styrene, n-butyl acrylate, and tert-butyl acrylate in bulk in the presence of the reversible addition-fragmentation chain-transfer agent dibenzyl trithiocarbonate is performed for the first time. The addition of trithiocarbonate makes it possible to prepare a narrowly dispersed visually optically transparent copolymer in a wide range of monomer-feed compositions even at limiting conversions. Conditions for the synthesis of acrylonitrile copolymers with controlled molecular masses and narrow molecular-mass distributions are ascertained. In the above copolymers, the trithiocarbonate group is shown to be located within the chain.
  • Article
    This chapter traces the development of addition-fragmentation chain transfer agents and related ring-opening monomers highlighting recent innovation in these areas. The major part of this chapter deals with reagents that give reversible addition-fragmentation chain transfer (RAFT). These reagents include dithioesters, trithiocarbonates, dithiocarbamates, and xanthates. The RAFT process is a versatile method for conferring living characteristics on radical polymerizations providing unprecedented control over molecular weight, molecular weight distribution, composition, and architecture. It is suitable for most monomers polymerizable by radical polymerization and is robust under a wide range of reaction conditions. It provides a route to functional polymers, cyclopolymers, gradient copolymers, block polymers, and star polymers.
  • Article
    Living/controlled radical polymerization (L/CRP) and soap-free emulsion polymerization have attracted much interest in recent years due to their great significance both in academics and in industry. Polymers with topological architectures and controlled molecular weight as well as controlled molecular weight distribution can be prepared by L/CRP method. As an environmentally friendly polymerization approach, soap-free emulsion polymerization can overcome the drawbacks of conventional small molecular surfactants that have negative effects on the properties of polymer products. Soap-free living radical emulsion polymerization combines the advantages of both L/CRP and soap-free emulsion polymerization. The soap-free living radical emulsion polymerization can be usually implemented via two methods. The first one is that a water soluble or amphiphilic polymer with an initiating group is synthesized firstly by living radical polymerization,then the polymer is dissolved or dispersed in water,followed by emulsion polymerization of a hydrophobic monomer to form an amphiphilic polymer product. Thus, the amphiphilic polymer product can solely stabilize the latex as a macro-emulsifier without adding any other small emulsifiers. This is the major approach used in literature. The second is to utilize directly a surface-active small molecular initiator in a soap-free emulsion polymerization of a hydrophobic monomer,and a macro-emulsifier as the final polymer product can be formed after polymerization. The paper summarized recent progress of soap-free living radical emulsion polymerization, mainly including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) soap-free emulsion polymerizations. However,there are still some problems in soap-free living radical emulsion polymerization such as complex reaction systems, unknown reaction process or phenomena, and loss of latex stability under harsh conditions.
  • Chapter
    A comprehensive overview of dispersed phase vinyl polymerizations is presented, not only for traditional aqueous systems but also for nonaqueous systems including organic solvents and solvents of emerging interest such as ionic liquids and supercritical carbon dioxide. This chapter details several polymerization processes used for making polymer particles ranging in diameter from <. 50. nm (microemulsion polymerization) to >1. μm (dispersion polymerization). The emphasis is on radical polymerization, but recent progress with several alternative mechanisms, including controlled radical, ionic, catalytic, and ring-opening metathesis polymerizations, is also presented. Industrial applications are described in addition to fundamental principles for each type of heterogeneous polymerization.
  • Article
    Controlled radical polymerization of 4-vinylpyridine (4VP) and N-acryloylpiperidine (API) by the RAFT process allowed preparation of well-defined double hydrogen bond accepting P4VP-b-PAPI diblock copolymers. The miscibility of this new monomer pair was studied via a random copolymer blend approach and resulted in a Flory–Huggins interaction parameter χ4VP,API ≈ 0.03, which is higher than the commonly used styrene/MMA couple, but lower compared to styrene/isoprene. This value was found to support the bulk phase behavior of a series of diblock copolymers as evidenced by SAXS and TEM. Highly ordered structures, including cylinders, lamellae and spheres, were identified in these materials, even in diblocks of higher molecular weight and broader distribution, while a disordered morphology was indeed observed in a symmetric, low molecular weight analogue.
  • Article
    The present paper describes the successful one-pot synthesis of self-stabilized particles composed of amphiphilic block copolymers based on poly(methacrylic acid) (PMAA) obtained by polymerization-induced self-assembly. First, controlled radical polymerization of MAA is performed in water using the RAFT process by taking advantage of our recent results showing the successful RAFT polymerization of MAA in water [ChaducMacromolecules 2012, 45, 1241−1247]. The so-formed hydrophilic macroRAFT agents are then chain-extended in situ with a hydrophobic monomer to form amphiphilic block copolymer chains of controlled molar mass that self-assemble into stable nanoparticles. Various parameters such as the pH, the molar mass and the concentration of the PMAA segments or the nature of the hydrophobic block have been investigated.
  • Article
    In an emulsion atom transfer radical polymerization (ATRP), escape of catalytic copper ion species from particle to aqueous phase represents one of the major challenges, which cause uncontrollable polymerization and/or unstable latex. We addressed this issue by employing a functional surfactant-ligand (SL) design as capture agent (CA), which prevented the copper species from escape in the emulsion ATRP. In this work, an emulsion ATRP of methyl methacrylate (MMA) mediated CuCl2/4,4-di(5-nonyl)-2,2’-bipyridine (dNbpy) was carried out with Brij-98 as surfactant in the presence of small amount CA. The CA molecules effectively captured dissociated copper ions inside particle and thus efficiently decreased copper ion concentration in the aqueous phase. Only 3wt% surfactant loading (0.6 wt% CA and 2.4 wt% Brij-98 based on MMA) was needed to achieve a well-controlled ATRP and to stabilize the emulsion system, which is a significant reduction from a typical 13~18 wt% often used in the works reported in literatures.
  • Article
    The reversible addition-fragmentation chain transfer (RAFT) copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) was studied in the presence of poly(ethylene oxide)-based macromolecular RAFT (macroRAFT) agents of the trithiocarbonate type (PEO-TTC) in solution and in aqueous emulsion. Firstly the formation of PEO-b-P(VDC-co-MeA) diblock copolymers was performed in toluene solution at 30 degrees C and a good control over the polymerization with high chain-end functionality was shown. A first aqueous emulsion copolymerization of VDC with MeA was performed using one of the amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers as macromolecular stabilizer. Then, in a series of experiments the PEO-TTC macroRAFT agents were directly tested as both chain transfer agents and stabilizing agents in similar conditions (aqueous batch emulsion copolymerization of VDC with MeA at 70 degrees C). The influence of the nature and concentration of the initiating system and the presence or not of a buffer were studied. We demonstrated that in simple conditions, nanometric latex particles composed of amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers formed by polymerization-induced self-assembly (PISA). It can thus be concluded that PEO-TTC macroRAFT agents are valuable non-ionic macromolecular stabilizers in the emulsion copolymerization of VDC and MeA and allow the formation of core shell diblock copolymer particles in the absence of free surfactant. However, when rather high molar masses of the hydrophobic PVDC-based block were targeted, the determined molar masses deviated from the theoretical values.
  • Article
    Amphiphilic organo-polyoxometalates (POMs) used in the radical emulsion polymerization of styrene allowed the preparation in aqueous medium of stable 50-100 nm polystyrene-POM composite latexes. Thanks to the presence of a trithiocarbonate group in the POM amphiphile, POMs could be covalently linked to the polymer particle surface. The chemical and catalytic integrity of the POMs was confirmed, and the POM-mediated surface photoactivity of the latexes was demonstrated by the spatially controlled nucleation of silver nanoparticles at the periphery of the composites. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Article
    Polymerization-induced self-assembly is demonstrated to be a valid strategy to prepare highly concentrated block copolymer nano-objects. Herein, an investigation on the growth of block copolymer nanoparticles through macro-RAFT agent-mediated dispersion polymerization was performed by employing the brush macro-RAFT agent poly[poly(ethylene oxide) methyl ether vinylphenyl] trithiocarbonate (PmPEGV-TTC) and the linear poly(dimethylacrylamide) trithiocarbonate (PDMA-TTC) as typical examples. Well-controlled dispersion RAFT polymerization employing either the brush or linear macro-RAFT agent was achieved, and uniform block copolymer nanoparticles were obtained. A decreasing number of block copolymer nanoparticles (Np) in the polymerization medium and an increasing aggregation number (Nagg) of the block copolymer nanoparticles during the nanoparticle growth were detected, and both particle-disassembly/reassembly and chain extension of the block copolymer contributing to the growth of the block copolymer nanoparticles were concluded. The present study is anticipated to be helpful to clarify the growth of block copolymer nanoparticles via polymerization-induced self-assembly under dispersion conditions.
  • Article
    Ab initio RAFT emulsion copolymerization of styrene (St) and acrylonitrile (AN) was investigated by using poly(acrylic acid)20-b-polystyrene5 trithiocarbonate as surfactant and RAFT agent. The well-controlled polymerization in terms of linear growth of molecular weight, low PDI, and little coagulum could be achieved only when the mass ratio m(St)/m(AN) was greater than 1:1 and suitable polymerization temperature depending on the monomer ratios. A significant amount of coagulum was formed when more AN was used. The gel effect, which led to the diffusion-controlled RAFT addition reactions in the late stage of the polymerization, played a significant influence on the PDI, the degree of which was highly dependent on the targeted molecular weight and monomer compositions. For the copolymerization of styrene and acrylonitrile with the azeotropic composition (75 wt % styrene), the gel effect could be relieved by increasing the reaction temperature from 70 to 90 °C after the nucleation period, resulting in PDI as low as 1.20. However, in the cases of the higher AN composition, the gel effect was still pronounced. Unexpectedly, the particle number was insensitive to the RAFT agent concentrations.
  • Article
    Full-text available
    The interface between nematic liquid crystal, 4-cyano-4'-pentylbiphenyl (5CB), and water in a transmission electron microscopy (TEM) grid cell coated with QP4VP-b-LCP (quaternized poly(4-vinylpyridine) (QP4VP) and poly(4-cyanobiphenyl-4'-oxyundecylacrylate) (LCP)) was examined for protein and DNA detection. QP4VP-b-LCP was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Quaternization of P4VP with iodomethane (CH3I) made it a strong cationic polyelectrolyte and allowed QP4VP-b-LCP to form complexes with oppositely charged biological species. Several proteins, such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ), were tested for nonspecific protein detection. By injecting the protein solutions into the TEM grid cell, the initial homeotropic orientation of the TEM grid cell changed to a planar orientation above their isoelectric points (PIs) due to electrostatic interactions between QP4VP (+charge) and proteins (-charge), which did not occur below the PIs of the tested proteins. Their minimum concentrations at which the homeotropic to planar configurational change (H-P change) occurred were 0.01, 0.02, 0.03, and 0.04 wt.% for BSA, ChTg, Hb, and LYZ, respectively. One of the strong anionic polyelectrolytes, deoxyribonucleic acid (DNA) (due to the phosphate deoxyribose backbone) was also tested. A H-P change was observed with as little as 0.0013 wt.% salmon sperm DNA regardless of the pH of the cell. A H-P change occurred in 5CB and was observed by polarized optical microscopy. This simple and inexpensive setup for nonspecific biomaterial detection provides the basic idea for developing effective selective biosensors by introducing specific binding groups, such as the aptamer and antibody.
  • Article
    In this study, ammonolyzed poly(styrene‐alt‐maleic anhydride) terminated with dithioester group can be self‐assembled into an amphiphilic macro‐reversible addition‐fragmentation chain transfer (RAFT) agent, and RAFT group will be located in the interface of oil and water. RAFT polymerization of styrene (S) and butadiene (B) will be confined in the interface. The main work is to study the effect of degree of aminolysis, reaction temperature, and ratio of S/B on the polymerization kinetics and living characters. The experimental results revealed that aminolysis of dithioester group would lead to retardation and loss of living characters under higher degree of aminolysis. Interfacially confined RAFT miniemulsion polymerizations were of relatively good controlled/living characters under lower degree of aminolysis before gelation. Increase of reaction temperature and ratio of S/B will accelerate the formation of gelation. Finally, styrene/butadiene copolymer nanoparticles with uniform particle size were formed, and because of microphase segregation “core–shell” morphology with polybutadiene core and polystyrene shell was seen obviously. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
  • Article
    Styrene/acrylonitrile (SAN) copolymers with low polydispersity M‾w/M‾n (1.10–1.30) are synthesized by nitroxide mediated polymerization (NMP) in dimethylformamide (DMF) solution with a succinimidyl ester (NHS) terminal group from the N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl) nitroxide] (SG1) residue. These copolymers are thermally stabilized by removing the SG1, and then modified to form primary amine end‐functional SAN (SAN‐NH2). Proton nuclear magnetic resonance spectroscopy (1H NMR) and Fourier‐transform infrared spectroscopy (FT‐IR) indicated that the amine group is effectively placed at the chain end at a level of 90%. SAN‐NH2 is reactively blended with maleic anhydride grafted poly(ethylene) (PE) at 20 wt.% loading at 180 °C and the resulting morphology is compared against the non‐reactive blend. Scanning electron microscopy (SEM) indicates finer SAN domains ∼ 1 µm which are thermally stable upon annealing in the reactive case. The dispersed SAN domains are reoriented using a channel die to impart elongated domains with aspect ratios ∼ 14, which would be desirable for barrier materials. Amine end functional poly(styrene‐acrylonitrile) (SAN) polymers are synthesized using nitroxide mediated polymerization for use in reactive extrusion with maleic anhydride grafted poly(ethylene). The synthesis and modification of the polymers is described, as well as a study into the microstructure of the polymer blends. Blend microstructure is modified to form lamellar domains of SAN.
  • Article
    The mechanism of charge-transfer complexation in electron-donor(D)/electron-acceptor(A) active layer was studied for a pseudo-binary blend model system, poly(4-vinyl pyridine) /[6,6]-phenyl-C61-butyric acid methyl ester in DMF. The time evolution of the system can be characterized by four distinct stages, i.e., induction, complexation, aggregation and precipitation, respectively. In the induction stage, the conformation of P4VP remained unchanged, while the UV-vis showed that the charge-transfer complexation had almost accomplished. In the complexation stage, each P4VP chains complexed with about 3 PCBM molecules at [4VP]/[PCBM]=57:1, and shrinked in size with almost no change in UV-vis spectrum. In the subsequent aggregation stage, P4VP/PCBM complexes aggregated with each other to form spherical aggregates with again unchanged UV-vis signals. FA model can be used to explain this mechanism. In the final precipitation stage, huge P4VP/PCBM agglomerate began to phase out. The almost unchanged UV-vis spectrum after the induction stage indicated that the electronic transition from ground to excited state is not necessarily to be influenced by any inter- or intra-polymer structural transition.
  • Article
    Reversible addition fragmentation chain transfer (RAFT) polymerization has made a huge impact in macromolecular design. The first block copolymers were described early on, followed by star polymers and then graft polymers. In the last five years, the types of architectures available have become more and more complex. Star and graft polymers now have block structures within their branches, or a range of different branches can be found growing from one core or backbone. Even the synthesis of hyperbranched polymers can be positively influenced by RAFT polymerization, allowing end group control or control over the branching density. The creative combination of RAFT polymerization with other polymerization techniques, such as ATRP or ring-opening polymerization, has extended the array of available architectures. In addition, dendrimers were incorporated either as star core or endfunctionalities. A range of synthetic chemistry pathways have been utilized and combined with polymer chemistry, pathways such as 'click chemistry'. These combinations have allowed the creation of novel structures. RAFT processes have been combined with natural polymers and other naturally occurring building blocks, including carbohydrates, polysaccharides, cyclodextrins, proteins and peptides. The result from the intertwining of natural and synthetic materials has resulted in the formation of hybrid biopolymers. Following these developments over the last few years, it is remarkable to see that RAFT polymerization has grown from a lab curiosity to a polymerization tool that is now been used with confidence in material design. Most of the described synthetic procedures in the literature in recent years, which incorporate RAFT polymerization, have been undertaken in order to design advanced materials. (C) 2011 Elsevier Ltd. All rights reserved.
  • Article
    The anionic polymerization of 4-vinylpyridine (4VP) has been investigated in 9/1 pyridine/THF at 0 °C. After characterization of the living character of 4VP polymerization, its copolymerization with tert-butyl methacrylate (tBMA) has been carried out also successfully. Their relative reactivity ratios have been determined. Solvent composition as well as temperature have been varied in order to evaluate their influence on the final molecular characteristics of the polymers. Finally, a new SEC methodology in 8/1/1 N,N-dimethylformamide/triethylamine/pyridine has been developed.
  • Article
    The average molar masses of styrene-maleic anhydride (SMA) copolymers, calculated from data obtained by size exclusion chromatography (s.e.c.), are often lower (by a factor of two) or higher (by a factor of eight) than the values expected from light scattering and viscometry. However, the polystyrene samples which are used as reference materials exhibit no such deviations. Therefore, the exclusion mechanism during the elution of SMA is significantly interfered with by certain adsorption and repulsion mechanisms, with these being dependent on the set of columns used, the comonomer content and the molar mass. This interference can be attributed to the existence of active polar sites on the packing and to partial ring opening of the maleic anhydride ring, thus resulting in the formation of a dicarboxylic acid species. Ring opening might also be followed by protolysis. This anomalous behaviour can be suppressed by the addition of 5 wt% acetic acid to the solvent used, i.e. tetrahydrofuran (THF). The presence of the acetic acid does not influence the intrinsic viscosity. Thus the coil dimensions (hydrodynamic volume) do not change and the universal calibration remains valid.
  • Article
    Reversible addition–fragmentation chain transfer polymerization (RAFT) was developed for the controlled preparation of polystyrene (PS)/poly(4-vinylpyridine) (P4VP) triblock copolymers. First, PS and P4VP homopolymers were prepared using dibenzyl trithiocarbonate as the chain transfer agent (CTA). Then, PS-b-P4VP-b-PS and P4VP-b-PS-b-P4VP triblock copolymers were synthesized using as macro-CTA the obtained homopolymers PS and P4VP, respectively. The synthesized polymers had relatively narrower molecular weight distributions (Mw/Mn < 1.25), and the polymerization was controlled/living. Furthermore, the polymerization rate appeared to be lower when styrene was polymerized using P4VP as the macro-CTA, compared with polymerizing 4-vinylpyridine using PS as the macro-CTA. This was attributed to the different transfer constants of the P4VP and PS macro-CTAs to the styrene and the 4-vinylpyridine, respectively. The aggregates of the triblock copolymers with different compositions and chain architectures in water also were investigated, and the results are presented. Reducing the P4VP block length and keeping the PS block constant favored the formation of rod aggregates. Moreover, the chain architecture in which the P4VP block was in the middle of the copolymer chain was rather favorable to the rod assembly because of the entropic penalty associated with the looping of the middle-block P4VP to form the aggregate corona and tailing of the end-block PS into the core of the aggregates. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1017–1025, 2003
  • Article
    Poly(styrene-co-acrylonitrile) (P(St-co-AN)) microspheres were prepared by emulsifier-free emulsion copolymerization of styrene and acrylonitrile. Presence of cyano groups on the surface of these microspheres was confirmed by X-ray Photoelectron Spectroscopic analysis. By the method of chemical metal deposition, nickel particles were formed and deposited on the surface of microspheres to form polymer metal composite microspheres which showed magnetic properties. Transmission electron microscope observation showed that nickel particles of small size (15–50 nm) were attached and distributed over the surface of P(St-co-AN) microspheres. X-ray diffraction proved that the nickel particles were in zerovalent state.
  • Article
    In this study, living free radical procedures are extended to reactive monomers such as maleic anhydride, by the use of a mixture of α-hydrido alkoxyamine, and nitroxide. In copolymerizations with styrene, the living nature of the polymerization is preserved, which leads to preferential consumption of functionalized block copolymers, whose molecular weights can be readily controlled up to 100000 while retaining low polydispersities.
  • Article
    Atom transfer radical polymerization (ATRP) was carried out to obtain well-defined poly(4-vinylpyridine). The linear increase of molecular weights with conversion was observed, and polymers with low polydispersities (Mw/Mn APEQ 1.1-1.2) were obtained. The best result was obtained using PECl as the initiator and CuCl/Me6TREN as the catalyst in alcohol solvent such as 2-propanol at 40°C.
  • Article
    The synthesis of block copolymers of 2- and 4-vinylpyridine (VP) by reversible addition-fragmentation chain transfer (RAFT) polymerization was discussed. All polymerization were conducted at 60 °C under a nitrogen atmosphere in septa-sealed vials. Absolute molecular weights were determined by online light scattering. Good end-group control was demonstrated by utilizing the resulting homopolymers as macro-chain-transfer agents.
  • Article
    Poly(acrylic acid), PAA, was prepared by controlled radical polymerization with reversible addition−fragmentation chain transfer. Using trithiocarbonic acid dibenzyl ester, 1, and trithiocarbonic acid bis(1-phenylethyl) ester, 2, as chain transfer agents (CTA), the polymerization is controlled for low ratios [AA]:[CTA]. At higher ratios, the polymerization is plagued by transfer to solvent. Transfer to polymer is also detected at high conversion, as shown by the presence of branches in NMR spectroscopy. In its neutralized form, PAA chains are not all terminated by a thiol end group, as shown by elemental analysis, thiol titration, and MALDI TOF MS. Finally, dispersion of CaCO3, kaolin, and TiO2 using these PAA reveals that the dispersion characteristics are significantly improved using low-polydispersity PAA.
  • Article
    An overview is given on an easy synthesis of carbonxyl-terminated trithiocarbonates. Telechelic carboxyl-terminated polymers are shown to be easily obtained when dicarboxyl trithocarbonate is employed. Bulk or solution polymerizations of alkyl acrylates, acrylic acid, and styrene are well-controlled. Some disproportionation at chain ends are observed with methyl methacrylate.
  • Article
    We have achieved living cationic polymerization of vinyl compounds, where control of the polymerization has long been considered very difficult, due to the instability of the highly reactive carbocationic growing species and their tendency to undergo chain-transfer reactions. In particular, a well-controlled polymerization of methyl methacrylate has been achieved with the ternary initiating system consisting of CCl4, RuCl2(PPh3)3, and MeAl(ODBP)2. Evidence suggests the polymerization to proceed by a radical mechanism. With the ternary initiating system, the polymerization of MMA occurred without an induction period, and monomer conversion reached 90% in 4 h.
  • Article
    Forces exerted between block poly(vinyl-2-pyridine)/polystyrene (PV2P/PS) copolymer layers adsorbed on mica substrates have been measured over the separation range 0-200 nm between the substrate surfaces. The PV2P block binds strongly to mica in a flattened configuration; the PS block is not bound directly to mica in our experiments. The PS block is held on the surface through its covalent bond to PV2P. The form and range of the force vs. separation curve depend upon block molecular weights and the thermodynamic quality of the immersion solvent for the PS chain. In the good solvent toluene, the PS chains are shown to be stretched away from the surfaces in extended configurations and to exert long-ranged, mutually repulsive forces when two layers are brought to a separation causing overlap of the PS chains. In the θ solvent cyclohexane, the range is reduced considerably due to configurational contraction and due to the diminished effects of binary interactions between polymer segments. The range of the forces observed and their dependence on block molecular weights can be explained by fairly simple arguments about the packing of polymer chains on the surface.
  • Article
    MALDI-ToF-MS mass spectra of copolymers contain a lot of information on both chain length distribution (CLD) and chem. compn. distribution (CCD). In this paper an approach for extg. detailed information from a MALDI-ToF-MS mass spectrum is presented that enables the study of microstructure for copolymers. More specifically, this paper is dealing with a polystyrene-block-polyisoprene copolymer, in which the growth of the second block is followed with MALDI-ToF-MS as a function of conversion. The technique is compared to 1H NMR for the evaluation of av. chem. compns., revealing that ionization efficiencies do not influence the obtained mass spectra. It is shown that MALDI-ToF-MS can ext. detailed information on the chain length distributions (CLDs) for both polystyrene and polyisoprene blocks. Using random coupling statistics, it is shown that the proposed anal. yields results with a high accuracy. [on SciFinder(R)]
  • Article
    The characteristic ratio C∞ and the entanglement molecular weight Me are two key molecular parameters that control melt viscoelasticity, solid mechanical (brittle/ductile) behavior, and adhesion of polymers. We show that the characteristic ratio C∞ and the entanglement molecular weight Me can be predicted from chemical structure by group additivity with uncertainties usually less than ∼ 7% for C∞ and ∼ 15% for Me, comparable with the accuracies of experimental values.
  • Article
    Surface characteristics of styrene/acrylamide copolymer latex particles prepared without emulsifier were investigated as a function of acrylamide fraction in charged monomers. The presence of swelling or water-soluble polymer layer at the particle surface was suggested, and its thickness increased with increasing acrylamide fraction. The surface charge densities by conductometric and potentiometric titrations wer about half that of polystyrene latex particles at low pH and they increased slightly with increasing pH. Regarding the heterocoagulation between styrene/acrylamide copolymer latex particles and polystyrene latex particles, the critical coagulation concentration of KCI decreased with increasing acrylamide fraction. The consideration in terms of the interaction due to electrostatic and van der Waals forces also suggested that the swelling or water-soluble polymer layer at the particle surface plays an important role.
  • It is shown that the entanglement junction may be modeled as a binary hooking contact of Kuhn nodes between two chains. The entanglement behavior is thus determined by chain tortuosity and given by Nv = (1/β)C, where Nv is the number of real or virtual skeletal bonds in an entanglement strand, C∞ is the characteristic ratio, α = 2 is the number of hooks involved at an entanglement junction, and β = 1/3 is the fraction of binary hooking configurations out of all possible configurations at a binary nodal contact. In other words, we have Nv = 3C, which is verified experimentally for 44 polymers, covering a wide variety of skeletal, pendant, and stereoisomeric (tacticity) structures. Since C∞ may be estimated by group additivity, the present equation may be used to predict the entanglement behavior from chemical structure.
  • Article
    The ionic equilibria for poly-4-vinyl pyridine (P4VP) and poly-2-vinyl pyridine (P2VP) were studied by physico-chemical techniques such as potentiometry, viscosity and NMR-1H. The mixture of ethanol (45 per cent w.p.) and water was used as solvent to obtain the total range of ionization (0-1). It was found that the dissociation constants of pyridine residue of polymers in the absence of electrostatic interaction (pK0 = 3·3-3·9) are lower than for the monomer analogues 4-ethylpyridine and 2-ethylpyridine (5·02) and depend on ionic strength (NaCl). A sharp decrease of pKapp at the beginning of titration and increase of specific viscosity for P4VP and P2VP are both explained by electrostatic interactions between positive charges forming during titration of the macromolecules. Most probably, these interactions act through the organic part of the macromolecule. On the other hand, it is shown by NMR-1H that sharp changes in pKapp and specific viscosity at the beginning of the titration are not associated with changes in the average conformation of the monomer unit in the polymer. This conformation can be destroyed only when the energy of electrostatic interactions is large enough and this occurs when the mean distance between positive charges is relatively short.
  • Article
    This paper describes a versatile and effective method for the control of free radical polymerization and its use in the preparation of narrow polydispersity polymers of various architectures. Living character is conferred to conventional free radical polymerization by the addition of a thiocarbonylthio compound of general structure S=C(Z)SR, for example, S=C(Ph)SC(CH3)2Ph. The mechanism involves Reversible Addition-Fragmentation chain Transfer and, for convenience of referral, we have designated it the RAFT polymerization. The process is compatible with a very wide range of monomers including functional monomers such as acrylic acid, hydroxyethyl methacrylate, and dimethylaminoethyl methacrylate. Examples of narrow polydispersity (≤1.2) homopolymers, copolymers, gradient copolymers, end-functional polymers, star polymers, A-B diblock and A-B-A triblock copolymers are presented.
  • Article
    Surface modification of Ar plasma-pretreated SiLK® film coating on (1 0 0)-oriented single crystal silicon wafer (the SiLK–Si substrate) via UV-induced graft copolymerization with 4-vinylpyridine (the P4VP-g–SiLK–Si surface) was carried out to enhance the adhesion of the vacuum deposited copper. The composition and morphology of the P4VP-g–SiLK–Si surface were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The 180°-peel adhesion strength of the copper film with the P4VP-g–SiLK–Si surface was about 2.5 N/cm. This adhesion strength was much higher than that of the copper film with the pristine or the Ar plasma-treated SiLK–Si surface. The strong adhesion of evaporated copper with the P4VP-g–SiLK–Si surface was attributed to the strong interaction of the copper atoms with the pyridine groups. The extent of copper diffusion into the P4VP-g–SiLK–Si film at the annealing temperature of 300 °C, was investigated by time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and compared to those of copper diffusion into the pristine and Ar plasma-treated SiLK–Si surfaces. The improved resistance of the P4VP-g–SiLK–Si surface to copper diffusion, probably arose from the strong interaction of the copper atoms with the grafted 4VP polymer.
  • Article
    A method is developed to enable emulsion polymerization to be performed under RAFT control to give living character without the problems that often affect such systems: formation of an oily layer, loss of colloidal stability, or loss of molecular weight control. Trithiocarbonate RAFT agents are used to form short stabilizing blocks from a water-soluble monomer, from which diblocks can be created by the subsequent polymerization of a hydrophobic monomer. These diblocks are designed to self-assemble to form micelles. Polymerization is initially performed under conditions that avoid the presence of monomer droplets during the particle formation stage and until the hydrophobic ends of the diblocks have become sufficiently long to prevent them from desorbing from the newly formed particles. Polymerization is then continued at any desired feed rate and composition of monomer. The polymer forming in the reaction remains under RAFT control throughout the polymerization; molecular weight polydispersities are generally low. The number of RAFT-ended chains within a particle is much larger than the aggregation number at which the original micelles would have self-assembled, implying that in the early stages of the polymerization, there is aggregation of the micelles and/or migration of the diblocks. The latexes resulting from this approach are stabilized by anchored blocks of the hydrophilic monomer, e.g., acrylic acid, with no labile surfactant present. Sequential polymerization of two hydrophobic monomers gives completely novel core-shell particles where most chains extend from the core of the particles through the shell layer to the surface.
  • Article
    Polymer synthesis by nitroxide living radical polymerization was discussed. The advantage of this method is its ability to accommodate functional groups and diverse families of monomers and copolymers and its stability of the initiating species. Results showed that a variety of chemical transformations can be performed with no deleterious effect on the initiating ability of the alkoxyamine initiator.
  • Article
    Atom transfer radical polymerization (ATRP) was discussed. The fundamentals of transition metal catalyzed ATRP were studied. Results showed that ATRP is an important tool for design and synthesis of novel materials, it also helps in preparation of polymers under facile conditions.
  • Water-Soluble Synthetic Polymers
    • W Smider
    (27) Smider, W. Water-Soluble Synthetic Polymers; Prentice Hall: Englewood Cliffs, NJ, 1974; Vol. II, pp 50-53.
    • J T Lai
    • D Filla
    • R Shea
    • J C J F Macromolecules Tacx
    • N L Meijerink
    Lai, J. T.; Filla, D.; Shea, R. Macromolecules 2002, 35, 6754-6756. (22) Tacx, J. C. J. F.; Meijerink, N. L. J.; Suen, K. Polymer 1996, 37, 4307-4310.
    • J S Wang
    • K Matyjaszewski
    (8) (a) Wang, J. S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117, 5614-5615. (b) Kato, M.; Kamigaito, M.; Sawamoto, M; Higashimura, T. Macromolecules 1995, 28, 1721-1723.
    • J Xia
    • X Zhang
    • K Matyjaszewski
    Xia, J.; Zhang, X.; Matyjaszewski, K. Macromolecules 1999, 32, 3531-3533.
    • D Benoit
    • C J Hawker
    • E E Huang
    • Z Lin
    • T P Russell
    • Macromolecules
    (7) (a) Benoit, D.; Hawker, C. J.; Huang, E. E.; Lin, Z.; Russell, T. P. Macromolecules 2000, 1505-1507. (b) Hawker, C. J.; Bosman, A. W.; Harth, E. Chem. ReV. 2001, 101, 3661-3688.
    • K Matyjaszewski
    • J Xia
    Matyjaszewski, K.; Xia, J. Chem. ReV. 2001, 101, 2921-2990.
    • G Hadziioannou
    • S Patel
    • S Granick
    • M Tirrell
    Hadziioannou, G.; Patel, S.; Granick, S.; Tirrell, M. J. Am. Chem. Soc. 1986, 108, 2869-2876.
    • J J Yuan
    • R Ma
    • Q Gao
    • Y F Wang
    • S Y Cheng
    • L.-X Feng
    • L Jiang
    Yuan, J. J.; Ma, R.; Gao, Q.; Wang, Y. F.; Cheng, S. Y.; Feng, L.-X.; Fan, Z. Q.; Jiang, L. J. Appl. Polym. Sci. 2003, 89, 1017-1025.
    • S Creutz
    • P Teyssié
    • R Jérôme
    • Y E Macromolecules Kirsh
    • O P Komarova
    • G M Lukovkin
    Creutz, S.; Teyssié, P.; Jérôme, R. Macromolecules 1997, 30, 1-5. (26) Kirsh, Y. E.; Komarova, O. P.; Lukovkin, G. M. Eur. Polym. J. 1973, 9, 1405-1415.
  • Emulsion Polymerization: A Mechanistic Approach
    • R G Gilbert
    (15) Gilbert, R. G. Emulsion Polymerization: A Mechanistic Approach; Academic Press: London, 1995.