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Coacervate complex formation between cationic polyacrylamide and anionic sulfonated kraft lignin

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Abstract

Polyelectrolyte complex formation (PEC) is a common phenomenon occurring when positively charged polymers react with anionic polyelectrolytes and other anionic substances. Our interest is in papermaking, where cationic polyelectrolytes are used as retention aids (flocculants) added to papermaking suspensions, which contain various dissolved anionic substances. In general, there are three types of polyelectrolyte complexes: soluble, colloidal and coacervate complexes, of which the latter two phase-separate. The formation of each individual type of complex depends on the chemical and physical properties of the two oppositely charged polyelectrolytes. The focus of this study is on the formation of the coacervate complex between various cationic polyacrylamides (cPAM) and anionic sulfonated kraft lignin (SKL). The reaction between cPAM and SKL was found to be nearly stoichiometric. The amount of insoluble PEC (i.e. colloidal and coacervate complex) was found to be constant for a given cPAM charge; however, the ratio between colloidal and coacervate complex varied depending on the molecular weight of cPAM used. The formation of the coacervate complex increased with increasing molecular weight of cPAM while low molecular weight cPAM formed predominantly colloidal complexes with SKL.

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... Polymer branching can similarly lead to the formation of more non-stoichiometric PECs, since charges at sites in the inner parts of the molecules can be inaccessible to the oppositely charged polyelectrolyte. The presence of salt makes the polyelectrolytes form denser structures, which can lead to deviations from 1:1 stoichiometry [8]. However, since the main driving force is the release of counterions, real deviation from 1:1 stoichiometry will likely start to occur when the Debye length starts to be of the same order of magnitude as the distance between two charges along the chain of the polyelectrolyte with the lowest charge density. ...
... The interfacial tension between these two phases was studied by Spruijt et al. [17], who found that it clearly decreased with increasing salt concentration. The formation of coacervate complexes from cationic polyacrylamide (CPAM) and sulphonated Kraft lignin was investigated by Vanerek and van de Ven [8], who found that the molecular weight of CPAM was a key factor in coacervate formation, since a shorter chain can more easily adopt a coiled structure, which will precipitate. According to the authors, soluble, colloidal, and coacervate complexes can form simultaneously. Potential applications for coacervates are as flocculants and retention aids in papermaking [8], as drug carriers [18], and in food applications, for example, as fat replacers [19]. ...
... The formation of coacervate complexes from cationic polyacrylamide (CPAM) and sulphonated Kraft lignin was investigated by Vanerek and van de Ven [8], who found that the molecular weight of CPAM was a key factor in coacervate formation, since a shorter chain can more easily adopt a coiled structure, which will precipitate. According to the authors, soluble, colloidal, and coacervate complexes can form simultaneously. Potential applications for coacervates are as flocculants and retention aids in papermaking [8], as drug carriers [18], and in food applications, for example, as fat replacers [19]. ...
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AKADEMISK AVHANDLING som med tillstånd av Kungliga Tekniska högskolan i Stockholm framlägges till offentlig granskning för avläggande av teknisk doktorsexamen torsdagen den 31 maj 2012, kl. 10.00 i sal F3, Lindstedtsvägen 26, KTH, Stockholm. Avhandlingen försvaras på engelska. Fakultetsopponent: Professor Regine v. Klitzing från Technische Universität Berlin, Tyskland.
... The drained water was centrifuged for 30 min at 30 000 rpm, and then the amount of polyelectrolyte-bound anionic groups remained in the supernatant was determined by the polyelectrolyte titration Terayama 1952;Wågberg et al. 1989). The water was carefully separated from the precipitate using a pipette. ...
... enthalpic favouring of mixing similar polymer structures. PECs can also be non-stoiciometric, because some charges may be inaccessible due to their structure, inability to reconform or the low charge density of polyelectrolytes (Ankerfors 2008; Koetz et al. 1996; Thünemann et al. 2004;Vanerek and van de Ven 2006). In addition, differences in mixing procedure or the history of complexation can lead to the different structures of PEC and they can even freeze the structure far off the thermodynamically most stable one (Dragan and Schwarz 2004;Thünemann et al. 2004). ...
... This deviates from the observations in low charged systems. PECs formed by low charge density (and high molecular weight) polyelectrolytes often form coacervates; liquid-like and mobile structures (Biesheuvel and Cohen Stuart 2004;Vanerek and van de Ven 2006). The size of A-PAM III/PDADMAC complex was larger over the entire charge ratios compared to that of A-PAM III/C-PAM IV. ...
Article
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The objective of this study was to investigate the effects of complexes formed by oppositely charged polyelectro-lytes on dewatering of cellulose suspension. The size and charge of the polyelectrolyte complexes were characterized by different methods (mobility, turbidity, particle size and viscosity). The properties of the complexes depended on the charge ratio, the charge density and the molecular weight of the polymers. The effects of the polyelectrolyte complexes on drainage and retention of papermaking stock were studied with a Dynamic Drainage Analyzer. The best dewatering performance was shown by the complexes of low charge density and high molecular weight anionically and cationically modified poly(acryla-mide) (A-PAM and C-PAM), while complexes formed by high charge density and low molecular weight polyelectrolytes had no clear effects on dewatering. It was shown that the use of the complexes of A-PAM and C-PAM as drainage and retention aids enhanced the drainability of cellulose suspension, compared to C-PAM alone. The optimum concentration range of the dewatering effect induced by A-PAM/C-PAM complexes was broader than that of a single C-PAM. The drainage efficiency of A-PAM/C-PAM complexes can be controlled by changing the amount of polyelectrolyte complex and the A-PAM/C-PAM ratio as well as the properties of the complex.
... Some negatively charged species, which will be covered in more detail later, include fatty acids, resin acids, released hemicelluloses and pectins, and fragments of lignin. In addition, various processes related to sulfite pulping, as in chemi-thermomechanical pulp (CTMP) production, tend to produce sulfonate groups, which then contribute to the charge of the associated paper machine process waters (Ström et al. 1979;Nyman and Rose 1986;Sjöström 1990;Zhang et al. 1994;Vanerek et al. 2006). When present in the colloidal material, the sulfonate groups provide a contribution of charge demand that is independent of pH. ...
... Such deposition was promoted by the presence of calcium ions. Vanerek and van de Ven (2006) likewise showed that interaction between cationic polyacrylamide (i.e. a retention aid polymer) and sulfonated kraft lignin yielded coacervate complexes, the properties of which depended strongly on the mixing ratios and other experimental conditions. ...
... Willis et al. (1987) reported molecular mass values for lignosulfonates in the range 11,000 to 61,000 g/mole. Vanerek and van de Ven (2006) found that such complexation led to coacervate formation, i.e. phase separation between polyelectrolyte-rich and poor phases. The interaction between the lignin species and cationic polyelectrolytes followed a stoichiometric relationship. ...
Article
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Dissolved and colloidal substances (DCS) in the process waters of paper machine systems can interfere with the retention of fine particles, retard the drainage of water from the wet web, and generally hurt the intended functions of various polyelectrolytes that are added to the process. This review considers publications that have attempted to characterize the nature and effects of different DCS fractions, in addition to some of the ways that paper technologists have attempted to overcome related problems. The consequences of DCS in a paper machine system can be traced to their ability to form complexes with various polyelectrolytes. Such tendencies can be understood based on a relatively strong complexing ability of multivalent materials, depending on the macromolecular size and charge density. Continuing research is needed to more fully understand the different contributions to cationic demand in various paper machine systems and to find more efficient means of dealing with DCS.
... Polymer branching can similarly lead to the formation of more non-stoichiometric PECs, since charges at sites in the inner parts of the molecules can be inaccessible to the oppositely charged polyelectrolyte. The presence of salt makes the polyelectrolytes form denser structures, which can lead to deviations from 1:1 stoichiometry (Vanerek and van de Ven 2006). However, since the main driving force is the release of counterions, it can be anticipated that real deviation from 1:1 stoichiometry starts to occur when the Debye length starts to be of the same order of magnitude as the distance between two charges along the chain of the polyelectrolyte with the lowest charge density. ...
... The coacervate is a liquid-like, mobile, and reversible structure (Biesheuvel and Cohen Stuart 2004a). The formation of such complexes, for example, from cationic polyacrylamide (CPAM) and sulphonated Kraft lignin, has been investigated (Vanerek and van de Ven 2006), and it was found that the molecular weight of the CPAM was a very important factor for coacervate formation, since a shorter chain can more easily adopt a coiled structure, which will precipitate. Potential applications mentioned in this study were flocculants and retention aids. ...
... PECs can also be formed from an added polyelectrolyte and polyions or other ionic material already present in the pulp, for example, lignin or colloidal fibre material (Nyström et al. 2004;Vanerek and van de Ven 2006). Generally, the complexation of the polyelectrolytes leads to a decrease of free polyelectrolyte in solution, which in turn leads to a lower viscosity of the water phase. ...
... Polyelectrolytes are macromolecules that have charged or chargeable groups when dissolved in polar solvents like water. Combining solutions of oppositely charged polyelectrolytes can lead to formation of layer-by-layer assemblies [1,2], soluble [3], liquid coacervate [4], gel-like [5] and even solid [6,7] polyelectrolyte complexes (PECs) that, in the latter three cases, phase separation takes place from solution. Polyelectrolyte complexes are a topic of considerable interest [1,[8][9][10][11] and have been used for a number of applications such as separation membranes [12,13], immobilization of enzymes [14] or cells [15], coatings [16], drug delivery [17,18], gene carriers [19,20], and extraction of proteins [21]. ...
... Coacervation efficiency increases with increasing MW of cPAM. Below the cPAM critical molar mass, colloidal complexes are formed instead [4]. Anionic polyphosphazenes can form microdroplets by NaCl-induced simple aqueous coacervation. ...
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The copolymers ofmethacrylic acid with 0–50 % of 2-(methacryloyloxy)ethyl acetoacetate, and the copolymers of 2-(methacryloyloxy)ethyl trimethyl ammonium chloride with 0–50 % of 2-aminoethyl methacrylate were prepared by free radical polymerization in various solvents. The polyelectrolytes were characterized by potentiometric titration, NMR, viscometry and size exclusion chromatographic techniques. Polyelectrolyte complex formation between oppositely charged polyelectrolytes with polymerbound (non)reactive polyelectrolytes was studied in the presence of NaCl and CaCl2 as a function of ionic strength. The physical nature and efficiency of polyelectrolyte complexes that form gels, liquid coacervates, or soluble complexes depend on variables such as ionic strength and charge ratio. The highest complexation efficiency was obtained when a 1:1 charge ratio was used. Liquid coacervates were obtained with high ionic strength NaCl. The inclusion of small amounts of CaCl2 led to drastic property changes in the polyelectrolyte complexes. The divalent calcium ion (Ca2?) displaced the poly[2-(methacryloyloxyethyl) trimethyl ammonium chloride] from the complexes and appeared as a new form of liquid coacervate in a range of ionic strength (50–200 mM CaCl2). The reactivity of the polyelectrolyte systemwas demonstrated by studying the formation of coacervate complexes. Herein, the feasibility of cross-linking of the resulting coacervate via complementary poly(methacrylic acid-co-2-(methacryloyloxy) ethyl acetoacetate)-bound acetoacetate groups with poly(2-(methacryloyloxy)ethyl trimethyl ammonium chloride- co-2-aminoethyl methacrylate)-bound amine groups is discussed in detail.
... The properties of the complexes formed in aqueous solutions by oppositely charged PEs have been characterised by various instruments, such as turbidimetry [26,30], atomic force microscopy [31] and electrophoretic mobility [32]. The reaction stoichiometry has been determined by polyelectrolyte titration [26,33,32], while the adsorption kinetics and the structural parameters of the PECs have been elucidated by static light scattering [28] and by reflectometry [34]. ...
Article
The adsorption of polyelectrolyte (PE) multilayers and complexes, obtained from both high- and low-charge polyelectrolytes, was studied on silica and on cellulose model surfaces by quartz crystal microbalance with dissipation (QCM-D). The film properties acquired with the different strategies were compared. When polyelectrolytes were added on an oppositely charged surface in sequence to form multilayers both the change in frequency and dissipation increased. The changes in frequency and dissipation were clearly higher if low-charge PEs were used in the multilayer formation. The substrate, silica or cellulose, did not affect the adsorption behaviour of low-charge PEs and only minor differences were seen in the adsorbed amounts and changes in dissipation of high-charge PEs between SiO2 and cellulose. The complexes formed by low-charge PEs had higher changes in frequency and dissipation at low ionic strength on both surfaces, while the complexes formed from high-charge polyelectrolytes adsorbed more at high salt concentration. The complexes of low-charge polyelectrolytes adsorbed more on silica, while the complexes formed by high-charge PEs formed thicker layers on cellulose. The charge ratio had a significant effect on the adsorption and the highest changes in frequency and dissipation were obtained in the anionic/cationic charge ratio of 0.5–0.6. Generally, the multilayers and complexes formed by low-charge polyacrylamides adsorbed highly and formed rather thick layers on both surfaces, unlike the high-charge PEs which formed thin layers using either one of the addition techniques.
... Note that the dosage of total starch (cationic starch and anionic starch, on a dry basis) was 5%, based on the dry weight of mineral filler particles, and the weight percentages of cationic starch and anionic starch in the total starch were 85% and 15%, respectively. anionic components present in a cellulosic fiber slurry (Vanerek and Van De Ven, 2006). ...
... To ensure proper dissolution of the polymers, each of the solutions was stirred for 2 hr using an impeller stirrer. 21 The nanoparticles, i.e. aqueous colloidal dispersion of silica, which were acquired from Eka Chemicals Inc., had the designations NP BMA 0 (low structure), NP 442 (medium structure), and NP 780 (high Structure). Before use, each of nanoparticle suspensions was diluted to one part per hundred from the as-received mixtures. ...
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In the manufacture of a paper product, the application of wet-end additives and the adjustments of various conditions can have major effects on the physical and optical properties of the final paper. In this study, we prepared paper handsheets and investigated the effects of many process variables, including the type and amounts of cationic polyacrylamide and colloidal silica, in addition to temperature, duration of mixing, hydrodynamic shear, pH, and variations in electrical conductivity due to salt addition. The most important effects were attributable to variations in the amount, ionic charge, and molecular weight of cationic polyacrylamide, as well as the type and amount of colloidal silica. Many of the observed effects could be explained in terms of fiber flocculation, and the adverse effect of flocculation on the uniformity of the paper, a factor that significantly affected the physical properties. An understanding of the relationships between chemical variables, hydrodynamic shear, and other system variables can be helpful in selecting optimal operating conditions to meet process requirements as well as physical properties of the resulting paper. A statistical analysis was carried out, using normalized coordinates, to show which of the independent variables had significant effects on the response variables.
... Basically they dissociate into a macromolecular ion and small counter ions, similar to their cross linked analogs that have found much uses as ion exchange resins. Combining solutions of oppositely charged polyelectrolytes can lead to formation of layer-by-layer assemblies [41,[51][52][53], soluble [54,55], liquid coacervate [56], gel-like [57] and even solid [58,59] polyelectrolyte complexes (PEC's) that in the latter three cases phase-separate from solution. ...
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The design of new technologies for treatment of human disorders is a complex and difficult task. The aim of this article is to explore state of art discussion of various techniques and materials involve in cell encapsulations. Encapsulation of cells within semi-permeable polymer shells or beads is a potentially powerful tool, and has long been explored as a promising approach for the treatment of several human diseases such as lysosomal storage disease (LSD), neurological disorders, Parkinson’s disease, dwarfism, hemophilia, cancer and diabetes using immune-isolation gene therapy.
... However, except for certain treatments involving aluminum ions near to neutral pH, most of the precipitated lignin was only loosely attached to the cellulose. Vanerek and van de Ven (2006) studied the complexation between cationic acrylamide copolymers and colloidally dispersed lignin; the phase behavior of the resulting mixtures depended on the molecular mass of the flocculant. Micic et al. (2003) studied the adsorption of a lignin model compound onto cellulose and observed a tendency for self-assembly into domains, not unlike real wood. ...
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Aqueous dispersions of lignocellulosic materials are used in such fields as papermaking, pharmaceuticals, and preparation of cellulose-based composites. The present review article considers published literature dealing with the ability of cellulosic particle dispersions (fiber, fines, nanorods, etc.) to either remain well dispersed or to agglomerate in response to changes in the composition of the supporting electrolyte solution. In many respects, the colloidal stability and coagulation of lignocellulosics can be understood in terms of well-known concepts, including effects due to osmotic pressure arising from overlapping electrostatic double layers at the charged surfaces. Details of the morphology and surface properties of lignocellulosic materials give rise to a variety of colloidal behaviors that make them unique. Adjustments in aqueous conditions, including the pH, salt ions (type and valence), polymers (charged or uncharged), and surfactants can be used to control the dispersion stability of cellulose, lignin, or wood-extractive materials to serve a variety of applications.
... This deviates from the observations in low charged systems. PECs formed by low charge density (and high molecular weight) polyelectrolytes often form coacervates; liquid-like and mobile structures(Biesheuvel and Cohen Stuart 2004;Vanerek and van de Ven 2006). The size of A-PAM III/PDADMAC complex was larger over the entire charge ratios compared to that of A-PAM III/C-PAM IV. ...
... Rigid polymers with uneven charge distribution, due to their inability to reconform, are more likely to form non-stoichiometric PEC. The presence of salt makes the polyelectrolytes form denser structures, which can lead to deviations from 1:1 stoichiometry (Vanerek and van de Ven, 2006). However, since the main driving force is the release of counterions, real deviations from 1:1 stoichiometry occur when the Debye length starts to be of the same order of magnitude as the distance between two charges along the chain of the polyelectrolyte with the lowest charge density. ...
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... The results of the Hausner ratio, Carr's index and angle of repose and density revealed that the powder is free-flowing with good flowability. These micromeritics properties of gum were supported by Aroshi Sharma et al. [48]. In a study by Aroshi et al., it was also observed that TGP had the Hausner ratio, Carr's index and angle of repose of 1.25, 18 and 35°, respectively; hence, the obtained results from the present investigation are in accordance with previous studies. ...
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Polyelectrolyte complexes are getting more attention owing to their formation by the interaction of opposite charges with the help of electrostatic force. Polyelectrolyte complexation reduces the toxic effects of the cross-linking agents. Polyelectrolyte complexescan be classified on various bases. The current report highlights properties, factors affecting it and various technologies. In the present report we intend to discuss the applications of polyelectrolyte complexes such as biomedical, controlled delivery, medicine, and area which can cause controlled release in different aspects. Patents related to these inventions are added along with their pivotal roles.
Article
Pretreatment of lignocellulosic materials involves the solubilization of hemicelluloses, small portions of the lignin, and such components. The hemicellulose solutions are hydrolyzed for downstream fermentation into biofuels or biomaterials. Hydrolyzates produced by pretreatment contain significant colloidal material that is anionically charged. Many of the compounds that are present in the hydrolyzates are inhibitory to fermentation and interfere with downstream separations. The flocculation of this colloidal material makes separations easier by sedimentation and can reduce the fouling tendencies of membranes. It can also reduce the toxicity of the hydrolyzates to fermentation micro-organisms. We studied the dynamics of flocculation of lignocellulosic hydrolyzates with a variety of flocculating agents: electrolytes (alum) and polymers (PEI, pDADMAC, CPAM). It was found that trivalent cations were the most effective suspension destabilizers among the electrolytes, while the cationic polymers could cause flocculation and also redispersion depending on their dosage levels. Flocculation reduced the hydrolyzates’ turbidity from >10000 to under 20. With PEI and pDADMAC, flocculation occurred rapidly when the zeta potential of the colloid was close to zero showing that charge neutralization is the significant destabilizing mechanism. At higher dosages, redispersion occurred indicating that patching is also important in flocculation. Flocculation by PEI was sensitive to pH (from hydrolyzate pH of 3 to 8) with increased dosage necessary at higher pH values. The cationicity of PEI is reduced at higher pH which results in loss of its effectiveness. On the other hand, the zeta potential was largely unaffected with CPAM dosage indicating the dominance of bridging flocculation. Floc sizes ranged up to 3 mm, depending on flocculant dose and pH.
Article
Photolysis and migration seriously reduce utilization efficiency of photosensitive agrochemicals, which leads to vast losses of ecological and economic benefits. Here we develop a novel method for preparing water-based coacervate as a stabilizer for photosensitive agrochemicals by utilizing single-chain/gemini surfactants and sodium lignosulfonate (SL), a renewable and ubiquitous biopolymer abandoned by pulping industry that presents excellent intrinsic ultraviolet (UV) resistance. Coacervates contain intricate nanoscale networks and abundant bound water, resulting in highly effective encapsulation of hydrophilic and hydrophobic solutes, and entanglement with the micro- and nanostructures of a superhydrophobic surface without sacrificing its ability to resist UV degradation. These coacervates display a high encapsulation efficiency for photosensitive abscisic acid (ABA) up to 90%, and resist UV degradation for 70 times longer than that in pure water, and act as an optimal substrate for the deposition of encapsulated agrochemicals on superhydrophobic leaves after high-speed impact. As a result, the drought resistance of wheat seedlings is significantly improved after spraying ABA protected by SL-coacervates, compared with free ABA, demonstrating that agrochemicals sequestered in coacervates effectively alleviate photolysis and migration loss. Thus, using a lignin-based coacervate can be used to potentially promote productive and sustainable agriculture, by serving as a highly efficient and environmental-friendly stabilizer for photosensitive agrochemicals used in pesticide applications.
Chapter
The use of polyelectrolyte complexes (PECs) provides new opportunities for surface engineering of solid particles in aqueous environments to functionalize the solids either for use in interactive products or to tailor their adhesive interactions in the dry and/or wet state. This chapter describes the use of PECs in paper-making applications where the PECs are used for tailoring the surfaces of wood-based fibres. Initially a detailed description of the adsorption process is given, in more general terms, and in this respect both in situ formed and pre-formed complexes are considered. When using in situ formed complexes, which were intentionally formed by the addition of oppositely charged polymers, it was established that the order of addition of the two polyelectrolytes was important, and by adding the polycation first a more extensive fibre flocculation was found. PECs can also form in situ by the interaction between polyelectrolytes added and polyelectrolytes already present in the fibre suspension originating from the wood material, e.g. lignosulphonates or hemicelluloses. In this respect the complexation can be detrimental for process efficiency and/or product quality depending on the charge balance between the components, and when using the PECs for fibre engineering it is not recommended to rely on in situ PEC formation. Instead the PECs should be pre-formed before addition to the fibres. The use of pre-formed PECs in the paper-making process is described as three sub-processes: PEC formation, adsorption onto surfaces, and the effect on the adhesion between surfaces. The addition of PECs, and adsorption to the fibres, prior to formation of the paper network structure has shown to result in a significant increase in joint strength between the fibres and to an increased strength of the paper made from the fibres. The increased joint strength between the fibres is due to both an increased molecular contact area between the fibres and an increased molecular adhesion. The increased paper strength is also a result of an increased number of fibre/fibre contacts/unit volume of the paper network.
Article
This paper presents a novel strategy to prepare nano-lignin and its composites with natural rubber. The nano- lignin was ontained by fabricating colloidal lignin-Poly (diallyldimethylammonium chloride) (PDADMAC) complexes (LPCs) via self-assembly technology. The characteristics of LPCs were investigated by zeta potential, dynamic light scat- tering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet - visible (UV-vis) absorption measurements. The results indicated that PDADMAC intensively interacted with lignin by cation-! and !-! interactions, and lignin particles were stable in aqueous solution with an average particle size less than 100 nm. LPCs accelerated the vulcanization of NR/LPCs nanocomposites. Morphological studies and Dynamic mechanical analysis (DMA) showed the homogeneous dispersion of LPCs in the NR matrix and the strong interfacial adhesion between them. The nanoscale dispersion of LPCs significantly enhanced the thermal stability and mechanical properties of NR/LPCs nanocomposites.
Article
The main purpose of the study was to find ways of strengthening paper made from old corrugated containerboard (OCC) using the addition of cationic polyacrylamide (cPAM) and starch (CS) in conjunction with anionic PAM (aPAM) and starch (AS). Through modifying the wet-end conditions and modes of addition, we searched for optimal conditions to enhance paper strength, while in the meantime considering estimates of the drainage performance, production cost, and machine runnability. The results indicated that Percol 182, a cPAM, had the best enhancing efficacies on the tensile, burst, and folding strengths of the resulting paper. The amphoteric PAMs, Hercobond 6350 and PS 1280, had slightly inferior performances. While the aPAM, Percol 155, contributed to the tensile strength that was only better than an anionic starch, which had the worst burst strength. The tearing strength was highest when PS 1280 was used. Drainage effects of the additives differed according to the type and dose of the polyelectrolyte. Percol 182 significantly increased the freeness of the pulp, allowing water to drain faster. Hercobond 6350 was next, while Percol 155 significantly decreased the freeness of the pulp. When applying a fixed cPAM and CS to moderate the doses of an amphoteric PAM or aPAM, paper strengths varied with the polyelectrolyte complex used. For paper tensile strength, a pulp concentration of 1.00% and a tensile index Percol 182 dose of 1.00% were optimal, and the tensile indices of the resulting handsheets were optimized. However, when the cost factor was considered, then sequential CS/Percol 155 addition at a 0.75/0.25% dose was effective in elevating the tensile performance. For tearing strength, the sequential addition of CS with PS 1280 at doses of 0.25/0.75% and 0.50/0.50% was better. When cost was considered, adding CS and AS sequentially at a 0.75/0.25% or 0.50/0.50% dose was optimal for strength enhancement.
Article
The use of polyelectrolyte complexes (PECs) provides new opportunities for surface engineering of solid particles in aqueous environments to functionalize the solids either for use in interactive products or to tailor their adhesive interactions in the dry and/or wet state. This chapter describes the use of PECs in paper-making applications where the PECs are used for tailoring the surfaces of wood-based fibres. Initially a detailed description of the adsorption process is given, in more general terms, and in this respect both in situ formed and pre-formed complexes are considered. When using in situ formed complexes, which were intentionally formed by the addition of oppositely charged polymers, it was established that the order of addition of the two polyelectrolytes was important, and by adding the polycation first a more extensive fibre flocculation was found. PECs can also form in situ by the interaction between polyelectrolytes added and polyelectrolytes already present in the fibre suspension originating from the wood material, e.g. lignosulphonates or hemicelluloses. In this respect the complexation can be detrimental for process efficiency and/or product quality depending on the charge balance between the components, and when using the PECs for fibre engineering it is not recommended to rely on in situ PEC formation. Instead the PECs should be pre-formed before addition to the fibres. The use of pre-formed PECs in the paper-making process is described as three sub-processes: PEC formation, adsorption onto surfaces, and the effect on the adhesion between surfaces. The addition of PECs, and adsorption to the fibres, prior to formation of the paper network structure has shown to result in a significant increase in joint strength between the fibres and to an increased strength of the paper made from the fibres. The increased joint strength between the fibres is due to both an increased molecular contact area between the fibres and an increased molecular adhesion. The increased paper strength is also a result of an increased number of fibre/fibre contacts/unit volume of the paper network.
Article
A comparative study of interaction of the cationic gemini surfactant tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) (14-4-14) with anionic polymer Sodium Carboxymethylcellulose (NaCMC) having two different molar masses was performed in water and isopropanol (IP)-water media. The interaction process was studied in detail using conductometry, tensiometry, turbidimetry and viscometry. At very low concentration, 14-4-14 monomers interact with the polymer; above the critical aggregation concentration (cac), small micelle like aggregates form complexes with the polymer. During interaction process, coacervates are formed beyond Cs (polymer saturation concentration) which initially grew by aggregation and stay in the solution throughout the process. The interaction process was affected by addition of isopropanol in the medium. The intrinsic viscosities of two NaCMCs were determined by using Huggins and Kraemer equations. Dynamic light scattering (DLS) study helps to determine the hydrodynamic size of the dispersed polymer and its surfactant-interacted complexes. The hydrodynamic size of the dispersed polymer and its interacted complex in IP-water media is lower than that obtained in aqueous solution. The surface morphology of the solvent removed polymer and its surfactant-interacted complex were examined using scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The pattern of the morphologies depends on the polymer-surfactant composition and solvent environment.
Chapter
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This chapter gives a general introduction to the book and describes briefly the context for which the editors established its contents. The characteristics of polysaccharides during fiber processing and several technical challenges are presented alongside opportunities for processing polysaccharide fibers with desired properties. This book is not the first survey dealing with the interest of polysaccharides fibers or materials derived from renewable resources since several monographs have been published in recent years. The common denominator to many of these collective overviews is the biodegradable blends character of the ensuing material. We have attempted to gather in the present volume what we feel is a more comprehensive collection of monographs with the materials science elements as the predominant feature. Of course, the making blends based fiber issues remain essential here, but within the primary focus spelled out in the title
Chapter
This chapter will discuss the recent advances on the cationic and anionic polysaccharides fiber and the effect on the paper properties
Article
Limited information is available on the interaction of anionically charged lignin and cationic particles, despite the promising use of anionic lignin as a coagulant and dispersant for suspension systems. The main objective of this study was to discover the fate of lignin on its interaction with rigid and soft surfaces. In this work, carboxymethylated lignin (CML) with two different charge densities were produced and their adsorption performance on gold and polydiallydimethyl ammonium chloride (PDADMAC)-coated gold surfaces was comprehensively studied. The viscoelastic properties of adsorbed CML on the gold surface was investigated by means of Quartz crystal microbalance with dissipation (QCM-D). A higher adsorbed amount and compact layer were observed for the adsorption of CML with a lower charge density of -1.16 meq/g (CML1). CML with a higher charge density (-2.92 meq/g), CML2, yielded a lower surface excess density of 2.31×10-6 mol/m2 and a higher occupied area per molecule (71.84 Å2) at the interface of water and gold sensor. Below and at equilibrium, CML2 generated a bulkier adsorption layer than did CML1 on the gold sensor and on PDADMAC-coated sensor. Studies on the layer-by-layer (LBL) assembly of CML and PDADAMC revealed that CML1 adsorbed more greatly than CML2 on PDADMAC, and it generated a thicker but less viscoelastic layer. In this system, the greater loss to storage modulus (G″/G)′value was achieved for CML2, indicating its looser structure in the LBL system. Studies on the LBL assembly of carboxymethylated xylan/PDADMAC and CML/PDADMAC provided concrete evidence for the fate of 3-dimensional structure of CML on its adsorption performance.
Article
Polyelectrolytes complexes (PEC) based on poly(epichlorohydrin-co-dimethylamine) (EPI-DMA) and poly(4-styrene-sulfonic acid-co-maleic acid) (PSSMA) for polyphosphates encapsulation were prepared for the first time. The sodium hexametaphosphate (SHMP) was used as a model polyphosphate in this work. A factorial design 2³ was applied to optimize PEC formulations. The resultant PEC suspensions were characterized by dynamic light scattering (DLS), zeta potential and encapsulation efficiency (EE) of SHMP. The best results were found by formulation using 1% (w/w) of EPI-DMA, 0.1% (w/w) of PSSMA and addition of SHMP before PSSMA. This optimized formulation was applied in real oil well conditions and showed good stability at 25°C and reduced stability with increasing temperature. PEC showed excellent inhibition efficiency against calcium carbonate scale with minimum inhibitory concentration (MIC) of 2.0 mg L⁻¹ at 100°C and 1000 psi. PEC suspension also showed exceptional performance on assessment to sandstone, improving not only the adsorption of the material on the rock grains but also the durability of the scale inhibitor squeeze process by 100%.
Article
Full-text available
Enzymatic saccharification is widely used for producing sugars from woody biomass while generating hydrolysis lignin as a by-product. Hydrolysis lignin produced in this saccharification process is under-utilized due to its poor solubility and reactivity. In this paper, hydrolysis lignin (HL) was polymerized with acrylic acid (AA) by using potassium persulfate as the initiator under alkaline aqueous conditions to produce coagulant and adsorbent to be used as aids in wastewater treatment processes. The polymerization produced soluble anionic polymers with a solubility of 5.1 g/L, charge density of − 6 mmol/g, and molecular weight of 3.8 × 10⁵ g/mol. This soluble AA-g-HL polymer removed 95% cationic dye (basic blue 41) from an aqueous system at 1.2 g/g by forming polyelectrolyte complexes with dye molecules. The insoluble AA-g-HL polymer removed 46% of cationic dye at the dosage of 3 g/g via adsorption. Experimental data were fitted into various isotherm and kinetic models to identify the best description of the adsorption systems, and the corresponding thermodynamic parameters were determined. The Langmuir isotherm model revealed that the maximum theoretical adsorption capacity of dye (227 mg/g) on insoluble AA-g-HL was higher than that (52 mg/g) on HL. The kinetics data followed the pseudo-second model. The thermodynamic parameters indicated that adsorption onto AA-g-HL was an exothermic spontaneous process. Both the mean free energy and the magnitude of free enthalpy change verified that the main mechanism was physical adsorption.
Article
Full-text available
Water soluble polyelectrolyte complexes (PECs) formed between polyaspartate (anionic polymer) and poly(trimethylammonium propyl methacrylamide chloride) (cationic polymer) were studied by flow field flow fractionation with on-line coupling multi-angle laser light scattering-quasi elastic light scattering-differential refractive index determination (F4/MALLS/QELS/DRI). The separation technique permits to characterize polydisperse PECs. The molar mass of the polycation (PC) influences the stiffness of the PECs and the proportion between single PECs (i.e. nPA/1PC) and multiple PECs (i.e. nPA/n'PC). High ionic strength with NaCl (>0.1 M) tends to break the multiple PECs while CaCl2 destroys PECs and leads to the formation of complexes polyaspartate/Ca2+. The studied PECs can be used as inhibitors to the calcite formation in the drilling fluids.
Article
Full-text available
This chapter presents selected ideas concerning complexes that are formed either by oppositely charged polyelectrolytes or by polyelectrolytes and surfactants of opposite charge. The polyelectrolyte complexes (PECs), which are surfactant-free, form typical structures of a low degree of order such as the ladder- and scrambled-egg structures. In contrast, polyelectrolyte-surfactant complexes (PE-surfs) show a large variety of highly ordered mesomorphous structures in the solid state. The latter have many similarities to liquid-crystals. However, as a result of their ionic character, mesophases of PE-surfs are thermally more stable. Both, PECs and PE-surfs can be prepared as water-soluble and water-insoluble systems, as dispersions and nanoparticles. A stoichiometry of 1:1 with respect to their charges are found frequently for both. Structures and properties of PECs and PE-surfs can be tuned to a large extent by varying composition, temperature, salt-concentration etc. Drug-carrier systems based on PECs and PE-surfs are discussed. Examples are complexes of retinoic acid (PE-surfs) and DNA (PECs). A brief overview is given concerning some theoretical approaches to PECs and PE-surfs such as the formation of polyelectrolyte multilayers.
Article
It is often difficult to retain fillers in paper containing mechanical pulp because retention aids which are effective in fine paper are inactive in mechanical grades. Research work indicates that the soluble and colloidal substances in a mechanical furnish render cationic retention aids inactive, and in addition, there are various contaminants at play. The author examines the impact of the latter and shows that the most detrimental are kraft lignin, lignosulphonate and carboxymethyl cellulose. However, when polyethylenimine is added to the furnish, electrostatic interaction plays a significant role in the mechanism of retention.
Article
The effect of dissolved and colloidal substances (DCS) on chemical-induced flocculation of a bleached mechanical pulp was probed using the technique of focused-beam reflectance measurement (FBRM), also known as scanning laser microscopy (SLM). Addition of DCS to washed fibres decreased the extent of aggregation induced by a cationic polyacrylamide (C-PAM) flocculant and colloidal sodium montmorillonite (NaM) or anionic colloidal silica (ACS). The flocculation activity of the sodium montmorillonite or anionic colloidal silica was more sensitive to DCS addition than that of the cationic flocculant. Addition of low MW, high charge-density cationic coagulants largely reversed the detrimental effects of the DCS and restored the flocculation induced by the C-PAM and the anionic colloidal silica. The DCS was separated into a dissolved and a colloidal component, and the effect of these individual constituents on the extent of aggregation induced by the C-PAM and the anionic colloidal silica was examined.
Article
This paper looks at some of the principal facts about detrimental substances, to give some new details about their interaction with other materials and to give a few examples of paper mills where the whole papermaking process was improved by adding process chemicals in spite of a large amount of detrimental substances in the paper stock or in the raw material. Detrimental substances are defined as the total amount of anionic oligomers and polymers and nonionic hydrocolloids. Chemically, these detrimental substances can be of a different organic and inorganic nature and of different origin.
Article
Untreated calcium carbonate pigments, both precipitated (PCC) and ground (GCC), behave similarly when dispersed in water. Their charge, either positive or negative, depends on the CaCO3 concentration and the purity of the water. However, in neither case is the charge strong enough to prevent aggregation of pigment particles. They aggregate at a similar rate and their surface charge is very sensitive to impurities in water. In the presence of cationic polyelectrolytes their behaviour depends on the type of adsorbed polymers. Highly charged polyethylenimine (PEI) stabilizes both PCC and GCC due to increased electrostatic repulsion. Polyacrylamide (PAM), on the other hand, flocculates both by a bridging mechanism. Low dosages of PAM cause flocculation of CaCO3 even in the presence of a large excess of dissolved anionics such as sulphonated kraft lignin.
Article
Formation of a polyelectrolyte complex was investigated as a function of pH by using carboxymethyl cellulose and poly(ethylenimine) as polyanion and polycation components, respectively. Experimental data on turbidity and conductometric and potentiometric titrations led to the conclusion that the formation of the polyelectrolyte complex did not obey stoichiometry. Such a result may be attributed to the less flexible nature of the polyanion molecular chains and to the distribution of ionizable groups on the chains of both components.
Article
This paper studies the interactions of three cationic polymers with components in suspensions of unbleached and peroxide bleached TMP and their isolated dissolved and colloidal substances in water. The polymers differed in their molecular mass, charge density, and degree of branching. Results from the study demonstrate that there are significant differences in the interactions of different cationic polymers with the components in mechanical pulp suspensions, this information can lead to better control of colloidal stability in papermaking.
Article
The deposition onto and detachment of calcium carbonate particles from cellophane and glass with and without retention aids, polyethylenimine and polyacrylamide, were studied under well-defined hydrodynamic conditions in a stagnation point flow field created in an impinging jet apparatus. With one exception, all deposition efficiencies were found to be in agreement with expectations based on electrostatic attractive or repulsive forces. The efficiency of deposition onto polyacrylamide-treated cellophane was found, however, not to be reduced by electrostatic repulsion, implying that polyacrylamide functions as a bridging agent.The bond strength between polyethylenimine and cellophane is shown to be much higher than the bond strength between polyethylenimine and pulp fibers. The calcium carbonate particles deposited onto cellophane using either of the retention aids were able to withstand shear rates of the order of 8000 s−1. These shear rates are comparable to the shear rates prevailing in a paper machine headbox.The lack of time for the establishment of an equilibrium ion concentration close to the surface of a dissolving calcium carbonate particle is shown to be responsible for the two to three orders of magnitude difference between experimentally observed dissolution rates and the much higher rates calculated for diffusion-controlled dissolution.
Article
A quantitative study has been carried out of the formation of polyelectrolyte complexes between calcium lignin sulphonate (LS) and three cationic polyelectrolytes, two polytrimethylaminoethylmethacrylates (I and II) with different molecular weight and one acrylamide copolymer. The parameters studied were the weight ratio of the oppositely charged polymers, the concentration of NaCl and the temperature. Separated molecular weight fractions of LS were studied in combination with I. The interactions were found to result in soluble complexes, colloids or macroscopic precipitates, mainly depending on the polymer weight ratio and the molecular weight of LS. For fractions with Mw was ⪢ 1000 the complexation between I and LS was stoichiometric when LS was present in excess of charge equivalence, resulting in formation of only macroscopic precipitate and quantitative precipitation. Soluble polyelectrolyte complexes were formed with LS if the Mw was < 1000 and I was in excess. Very stable colloids were formed with this LS fraction and I. In unfractionated LS, these soluble complexes are probably adsorbed on precipitating particles containing high molecular weight LS and I.
Article
The rate of deposition of clay particles on fibers dispersed in water was determined as a function of the amount and the sequence of poly(ethylenimine) addition. The polymer was introduced either to a mixture of fibers and clay or to only one of the components prior to addition of the second one. The primary role of the positively charged polymer was to adsorb onto the negatively charged components, thus modifying their surfaces and consequently promoting their interaction.It has been established that the extent and rate of particle deposition result from an interplay of several kinetic factors, namely the rate of polymer adsorption on fibers and on clay, the rate of collision between clay particles and fibers, and the rate of clay particle aggregation. Under the conditions of low shear rate, the polymer adsorption on fibers is a rather slow process and is comparable to the rate of deposition of dispersed clay particles on fibers. In contrast, polymer adsorption on clay particles proceeds at a faster rate, causing aggregation of the particles. The deposition of aggregates is considerably faster than that of dispersed clay particles.
Article
The precipitation of kraft lignins with cationic polymers was investigated. Eighty to ninety percent of the lignin could be precipitated with polyamines or poly(diallyldimethylammonium chloride). The yield of precipitate was not sensitive to the molecular weight of the cationic polymer, the concentration of sodium chloride or the detailed chemical structure of highly charged cationic polymers.
Article
The adsorption and adsorption stoichiometry for a series of high molecular weight cationic polyacrylamides of different charge density on cellulosic fibers are examined as functions of time. The time required for the reconformation of the polymer adlayer is of the order of one minute in all cases, but the results indicate a decrease in adsorption stoichiometry and reconformation rate with increasing polyelectrolyte charge density. Comparison of the adsorption/reconformation rates on cellulosic fibers with those on polystyrene latex shows the process to be more rapid for the latex. This result is attributed primarily to differences in the surface porosity of the substrates.
Article
Interpolymer complex formations of poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) with oligocations as well as poly(ethylene oxide) (PEO), and poly-(N-vinyl-2-pyrrolidone of various chain lengths were studied. For the case of complexation between PMAA and oligocations, the standard free energy change for the complexation ΔG° was found to be linearly dependent on the number of interacting sites, n. The stability constant K for complex is expressed as K = Aewhere A and B are constants which depend on the chemical structure of the polyelectrolytes. For the case of complex formation through hydrogen bonding, the degree of linkage Θ, defined as the ratio of the binding groups to the total of potentially interacting groups, and the stability constant K of the polymer-polymer complexes both in aqueous and aqueous-alcoholic media were determined as a function of temperature by means of potentiometric titration. It was found that Θ and K were strongly dependent on chain length, temperature, and medium, and that hydrophobic interaction was a significant factor for the stabilization of the complexes. The enthalpy and entropy changes as well as the cooperativity parameter of the complex formation, derived by use of a one-dimensional Ising model, were also calculated. Both of these two types of interpolymer complexes were found to be in a nonequilibrium state for a considerable period of time, and they grow to an interesting morphological structure after successive aggregation. A mechanism for the complexation process was proposed in terms of the cooperative interaction.
Article
Polyelectrolyte complex formation between components with strong ionic groups and high molecular weights were studied by static light scattering as a function of the mixing ratio and the ionic strength of the medium. Sodium poly(styrenesulfonate) and sodium poly(methacrylate) were used as polyanions and poly(diallyldimethylammonium chloride) and its copolymer with acrylamide were used as polycations. Very small amounts of sodium chloride lead to a drastic decrease of the level of aggregation, while higher ionic strength results in macroscopic flocculation.
Article
A viscometric analysis for studying the polyelectrolyte complexation mechanism of sodium poly(styrenesulfonate) (NaPSS) by addition of diallyldimethylammonium chloride−acrylamide copolymers (DADMAC−AAM copolymers) was developed. The viscosity of the reacting mixture was studied as a function of the mixing ratio (ratio of the polycationic to polyanionic groups). A minimum viscosity (point of equivalence) was observed for an equimolar mixing ratio, thus indicating a 1:1 stoichiometry of the polyelectrolyte complexes (PECs) at this point. With an increase of the cationic charge density (35−100%) of the copolymer, the packing density of the complexes increased (8−60 mg/mL). For a charge density below 35% of the copolymer, flocculation occurred before the equimolar mixing ratio was reached. This was due to the larger size of the formed aggregates. To obtain additional structural information (stoichiometry, density) on the PECs before or after the point of equivalence, the contributions of the free polyelectrolyte in excess and of the PEC to the specific viscosity of the reacting mixture were estimated. Nonstoichiometric PECs were shown to be formed before the point of equivalence. Factors of stoichiometry (ratio of polyanionic to polycationic groups in the PECs) were evaluated to 1.4−1.6. The polyanionic excess tended to be lower at high cationic charge density and disappeared with increasing the mixing ratio until an equimolar ratio was reached. After the point of equivalence, the swelling of the PEC dominated.
Article
Reaction of the strongly ionized, oppositely charged polyelectrolytes sodium (polystyrenesulfonate) and poly(vinylbenzyltrimethylammonium chloride) leads to the formation of a compact precipitate over the entire range of relative concentrations. Conductometric studies show that the reaction is stoichiometric and that the pairing of ionic functions in the complex is complete for the reaction in salt-free solutions or even in 10-2 N NaCl. Addition of divalent-univalent salt, e.g., CaCl2, results in deviations from stoichiometry but only on one side of the equivalence point. Reaction of the polyacid and polybase, even in the presence of electrolyte, results in deviations from stoichiometry on both sides of the equivalence point and film fragments rather than the usual discrete particles. The deviations from stoichiometry in the first case can be related to the more tightly coiled configuration of one of the polyions in the presence of its divalent counterions and in the second to the rapid reaction of acidic and basic functions which results from neutralization of the counterions. This suggests that two requirements for the unusual stoichiometric reaction are an open-chain conformation and the moderating effect of salt-type counterions.
Article
The precipitation of kraft lignin with poly(diallyldimethylammonium chloride), poly(DADMAC), was characterized as a function of pH. At a mass mixing ratio of poly(DADMAC) to lignin of 0.53 at pH 12.6, approximately 80% of the added lignin was removed, whereas the precipitate contained less than 35% of the added poly(DADMAC). Lignin precipitated with as much as 75% of the charges not associated with poly(DADMAC). Lower pH solutions required less poly(DADMAC) for lignin precipitation. Colloidal complex formation was measured as a function of time by dynamic light scattering, and the results could be fitted by a diffusion-controlled aggregation model.
Article
The alkaline hydrolysis of two acrylamide-based polyelectrolytes has been investigated. The experiments were carried out in buffered aqueous solutions in the pH range of 3.5–8.5 and in the temperature range of 22–50°C. 13C-NMR analysis of the hydrolysis product showed that choline chloride was the substance released upon hydrolysis. The decrease in charge density of the copolymer due to the hydrolysis was studied by polyelectrolyte titration and nitrogen analysis. The results show that the rate of hydrolysis increased with increasing pH or increasing temperature. In the hydrolysis of C-PAM 1 at 22°C and pH 6, the half-life of the cationic groups was 10 days. At pH 7 the half-life was shorter, 24 h, and at pH 8.5 the reaction was very fast with a half-life of about 0.25 h. The charged groups on C-PAM 2, the polymer with the higher charge density of the two polymers studied, have somewhat longer half lives than those on C-PAM 1. This can be explained by the structure of the polymers.
Article
Polymer complexes were formed through electrostatic interaction in poly(methacrylic acid)-integral type polycation systems and hydrogen bonding in the poly(methacrylic acid)-poly(N-vinyl-2-pyrrolidone) system in several solvents. The composition of the polyelectrolyte complex was affected by the chemical properties of solvents, e.g., the dissociation of the component polyelectrolyte was interferred with decreasing the polarity of the solvent. The heats of mixing in case of the combination of poly(methacrylic acid)-poly(N-vinyl-2-pyrrolidone) were negative in N,N-dimethylformamide but they were positive in water. In polyelectrolyte complex systems, they could not be measured by reason of some experimental difficulties. These results indicate that solvation of the component polymers is very important to clarify the mechanism of the formation of polymer complexes.
Article
Mixtures of a weak polybase (polyethylenimine) and a weak polyacid acrylamide-acrylic acid copolymer in aqueous solutions at several ionic strengths and polymer concentrations are studied potentiometrically. When the concentrations of the polyethylenimine and acrylamide-acrylic acid copolymer charges are not too different, phase separation into two liquid phases (“complex coacervation”) is observed. In the pH region where no phase separation occurs, potentiometric titrations are performed on mixtures of both polymers. From the titrations of polyethylenimine solutions, acrylamide-acrylic acid copolymer solutions, and the mixtures, the free energy of interaction has been evaluated according to the theory of Litan. The dependence of the free energy of interaction on pH, polymer concentrations, and ionic strength is explained quantitatively with a model of cooperative electrostatic physical association.
Article
Polyelectrolyte complex formation between polyanions and polycations with strong ionic groups and high molecular weights in pure water results in highly aggregated compact and nearly spherical particles, consisting of a neutralized core and a stabilizing shell of the excess component. The response of such systems to the addition of sodium chloride was studied by turbidimetry and static light scattering in relation to the ionic group of the polyanion (Na-poly(styrene sulfonate) and Na-poly(methacrylate)) and the charge density of the polycation (poly(diallyldimethylammonium chloride) and its copolymers with acrylamide). While in the systems with Na-PSS the addition of salt causes mainly additional aggregation and macroscopic flocculation, redissolution of the complexes with Na-PMA at a critical salt concentration was found. The use of the copolymers with hydrophilic acrylamide as excess component leads to a stabilization against additional aggregation.
Article
We have prepared cationic polyelectrolytes with a large range of compositions by the redox polymerization and copolymerization of acrylamide and (N,N,N-trimethyl) aminoethyl chloride acrylate. Molecular weights of the various samples were determined by light scattering, and the intrinsic viscosities of these polymers measured in aqueous solutions of various ionic strengths. We propose empirical laws between viscosity, composition in comonomers, molecular weight and ionic strength. Results also give the radius of gyration of macromolecules in NaCl solution (between 10−2M and 1 M).
Article
The effect of cationic polyethylenimine on the mutual attraction between fibers and clay particles is documented by comparing the clay content of sheets of paper formed from a mixture of fibers and clay with the change in their electrophoretic mobilities resulting from the polymer adsorption. The maximum clay deposition on fiber takes place when the fibers and clay are oppositely charged thus providing evidence that an electrostatic interaction plays an important role in the retention mechanism.The presence of anioic substances (kraft lignin, carboxymethyl cellulose) capable of forming complexes with the cationic polymer requires an excess of polyethylenimine to affect the charge of the solid particles and thus promote their mutual attraction. Carbohydrates (starch and xylan) are less detrimental to the performance of polyethylenimine.
Article
The formation of polyelectrolyte complexes between pine xylan (6.5% uronic acid) and three cationic polymers (polyethyleneimine, and two acrylamide/acrylamine co-polymers) has been studied as a function of pH and ionic strength. Complex formation is not stoichiometric and both soluble and insoluble complexes are formed with maximum precipitation occurring when the complexes are neutral. At low ionic strength, complex formation can be reversed by increasing the ionic strength but not by dilution or by changing the relative concentration of the polymers. The driving force for complex formation thus appears to be non-specific electrostatic interactions. A tentative structure for the complexes is suggested.
Biological Polyelectrolytes
  • A Veis
  • Dautzenberg