Zdeněk Tuzar’s research while affiliated with Czech Academy of Sciences, Institute of Macromolecular Chemistry and other places

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Publications (87)


Figure 3. Structure factor S(q) experimentally obtained for a solution of the PS-PEP diblock copolymer with polymer concentration 5% (w/w) and solvent composition CX/12% DMF (filled symbols), and calculated structure factor (solid line) obtained by isotropically averaging scattering from a finite-size crystal with BCC structure and 6 scattering centers per principal axis. 
Figure 4. Two-dimensional structure factor S eff (q,φ) obtained by dividing the measured 2-dimensional SAXS diffractogram I(q,φ) with the calculated form factor F(q). The intensity scale is identical to that of Figure 3, i.e., linear and goes from 0 to 6. The full and dotted lines represent the reciprocal lattice for a twinned BCC structure with common < _ 111> axis parallel to the flow direction → V and the < _ 112> axis parallel to the neutral direction → e. The indexing is given for the grid marked by full lines and refers to lattice points to the left of the index. 
Figure 3 of 3
Structure of self-organized diblock copolymer solutions in partially miscible solvents
  • Article
  • Full-text available

March 2010

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114 Reads

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2 Citations

Physical Chemistry Chemical Physics

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Zdenek Tuzar

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Petr Kadlec

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A diblock copolymer dissolved in a mixture of partially miscible solvents creates a self-organized microemulsion with a morphology that depends on the numerous parameters of the system. We discuss one particular case of spherical particles (containing the minority solvent) forming a hard gel with cubic structure and demonstrate using high-resolution synchrotron scattering experiments that the self-organized solution has a BCC structure. After fitting one- and two-dimensional form factors we extract from the data the one- and two-dimensional structure factors, S(q) and S(q,phi). The experimental S(q) corresponds almost quantitatively, up to the 9th order Bragg peak, to that calculated numerically for a randomly-oriented, finite-size BCC crystal. S(q,phi) contains a large number of reflections that allow the structure to be identified more exactly as a twin BCC morphology with some imperfections. Examination of the dependence of the structural parameters on polymer concentration reveals that the dilution law predicted theoretically for the center-to-center distance of the spheres is confirmed experimentally while the size of the spherical objects does not follow theoretical predictions due to chain extension with increasing concentration.

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Hydration Modes of an Amphiphilic Molecule: NMR, FTIR, and Theoretical Study of the Interactions in the Water-Lutidine System

September 2009

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45 Reads

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10 Citations

The Journal of Physical Chemistry B

Using (1)H and (13)C NMR spectra and relaxations, PFG NMR diffusion measurements, FTIR spectra, and quantum-chemical structure predictions and optimizations on the MP2/6-31G(d) level, we have studied interactions between water (W) and lutidine (2,6-dimethylpyridine, L) in a wide range of ratios. At low W content up to 35%, W was found to bind to L by an O-H***N hydrogen bond and form transient L-W aggregates containing two to four L molecules in cooperation with two to three other W molecules. At higher W content, these aggregates are gradually cleaved to single L molecules enwrapped by a hydration shell anchored in an O-H***N hydrogen bond. At all compositions of the mixture, the various hydrate forms are in fast mutual exchange with a correlation time on the order of 1 x 10(-5) s.


Hybrid Polymeric Micelles Based on Poly(styrene-b-2-vinyl-1-methylpyridinium iodide-b-ethylene oxide) and Tungstate

April 2009

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30 Reads

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2 Citations

Polymer Journal

Poly(styrene-b-2-vinyl-1-methylpyridinium iodide-b-ethylene oxide) (PS-PVMP-PEO) was synthesized by quaternizing poly(2-vinyl pyridine) block of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) with iodomethane. Then, PS-PVMP-PEO/ tungstate hybrid micelles were prepared by binding tungstate to the PVMP block at neutral pH in aqueous solutions. The hybrid micelles were characterized by various techniques like dynamic light scattering, scanning electron microscopy, transmission electron microscopy, and zeta-potential measurements. It was found that the PS-PVMP-PEO/tungstate hybrid micelles have a spherical structure with a hydrodynamic diameter ranging from 80 to 120 nm depending on the amount of the incorporated tungstate.Keywords: Triblock Copolymer, Core-Shell-Corona, Tungstate, Hybrid Micelle, Stimuli-Responsive Micelle


Complex Structure and Dynamics of Diblock Copolymers in a Mixture of Partially Miscible Solvents

February 2008

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9 Reads

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1 Citation

We have investigated the structure of self‐organized microemulsions made of two partially miscible solvents emulsified by a diblock copolymer. We have found that above the phase separation temperature Tc the solution is almost homogeneous while at temperatures below Tc the solution is microphase separated into a periodic lattice generally with body centered morphology. The lattice points are occupied by micelles that contain the minority solvent. Transmission electron microscopy shows that the micelles are first formed at random positions in the sample in the vicinity of Tc and on further cooling they self‐organize into the three‐dimensional network. The dynamical properties of this system were investigated by dynamic light scattering and pulsed‐field gradient NMR. Seven processes could be identified that correspond to (in order of increasing relaxation time) thermal diffusion, self‐diffusion of solvent molecules, cooperative diffusion, self‐diffusion of polymer chains, self‐diffusion of micelles, cluster diffusion and diffusion of grains.


Three-Dimensional Analysis of Dynamic Light Scattering Data: Application to Self-Organized Polymer Solutions

January 2007

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10 Reads

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6 Citations

International Journal of Polymer Analysis and Characterization

Semi-dilute solutions of diblock copolymers in selective partially miscible solvent mixtures have been studied by dynamic light scattering and pulsed-field gradient NMR. Several dynamic modes have been identified as cooperative diffusion, polymer self-diffusion, and cluster diffusion. Their temperature dependences changed dramatically at a certain temperature, below which solutions underwent self-organization. Interpretation of the complex behavior of the dynamic processes observed has been made. The importance of a 3-D representation of the distributions of relaxation times is demonstrated.


New insights on the solution behavior and self-assembly of polystyrene/poly(2-vinylpyridine) ‘hairy’ heteroarm star copolymers with highly asymmetric arms in polar organic and aqueous media

November 2005

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52 Reads

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35 Citations

Polymer

The solution behavior and self-assembly of a ‘hairy’ heteroarm star copolymer polystyrene/poly(2-vinylpyridine) containing 20 fairly short polystyrene and 20 long poly(2-vinylpyridine) arms was studied in 1,4-dioxane–methanol mixtures and in acidic aqueous solutions. The copolymer forms reversible micelles in 1,4-dioxane–methanol mixtures. Since the conformation of the unimolecular heteroarm star (unimer) with collapsed insoluble PS arms and stretched soluble PVP arms resembles the spherical core/shell micelle, the solubility of the copolymer in the selective solvent is fairly high and the multimolecular micelles are formed by only few heteroarm stars. Both heteroarm stars (in pure 1,4-dioxane) and micellar systems (composed of both micelles and unimolecular heteroarm stars (unimers) in 1,4-dioxane–methanol mixtures) may be transferred in acidic aqueous media by dialysis. Polyelectrolyte behavior of unimer stars was studied in detail in acidic aqueous media. Static and dynamic light scattering measurements show that heteroarm stars interact electrostatically over long distances in low ionic strength solutions. Experimental data indicate that the charged stars may form temporary shell interacting (electrostatically stabilized) aggregates at elevated concentrations.


Small-Angle Neutron Scattering from Solutions of Diblock Copolymers in Partially Miscible Solvents†

March 2005

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9 Reads

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12 Citations

Macromolecules

We report on small-angle neutron scattering experiments from diblock copolymers A−B dissolved in a mixture of partially compatible solvents a and b (an extended abstract of this work has been published in Bull. Am. Phys. Soc. 2004, March). Block A is polystyrene, while block B is polyisoprene, polybutadiene, or hydrogenated polyisoprene. Solvent a is dimethylformamide, which is a good solvent for block A and a bad solvent for block B, and vice versa for solvent b, namely, cyclohexane. There is a range of temperatures and concentrations somewhat above as well as below the coexistence curve of the two solvents where the samples, though remaining macroscopically homogeneous, are microphase-segregated, presumably between a-rich and b-rich domains separated by interfaces covered with the diblock copolymer. For the various copolymers studied, we find cubic or hexagonal structures with local order only at high temperatures, but long-range ordered structures below the coexistence curve. The characteristic structural dimensions are in the range 60−110 nm and depend on both the polymer concentration and relative amount of solvents. We also show that the chains at the interface are slightly extended, as described by the value a = 0.65 of the Flory exponent that exceeds the value for free chains with excluded volume, a = 0.60.


Amphiphilic Block Copolymer Micelles with Hydrophobically Modified Shells

October 2003

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9 Reads

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3 Citations

Molecular Simulation

The conformational behavior of hydrophobically modified shell-forming poly(methacrylic acid) (PMA) blocks in 1,4-dioxane–water solutions of polystyrene-block-poly(methacrylic acid) (PS-PMA) micelles was studied by a combination of several experimental methods (static and quasielastic light scattering, fluorescence techniques and atomic force microscopy). The nonradiative energy transfer (NRET) studies with fluorescently tagged samples show that the hydrophobic anthracene groups attached to the ends of PMA blocks try to avoid the aqueous medium and return closely to the PS core, forcing PMA chains to loop back. Computer modeling (Monte Carlo and mean-field calculations) was performed to get better insight into the conformational behavior. Computer studies reproduce the behavior on the semi quantitative level.


Hybrid Block Copolymer Micelles with Partly Hydrophobically Modified Polyelectrolyte Shells in Polar and Aqueous Media: Experimental Study Using Fluorescence Correlation Spectroscopy, Time-Resolved Fluorescence, Light Scattering, and Atomic Force Microscopy †

August 2003

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8 Reads

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36 Citations

The Journal of Physical Chemistry B

The structure and behavior of amphiphilic block copolymer micelles with partly hydrophobically modified polyelectrolyte shells were studied in 1,4-dioxane-water mixtures and in purely aqueous media by a combination of several experimental techniques. The studied hybrid micelles are formed by 20 wt % of a modified polystyrene-block-poly(methacrylic acid), PS-N-PMA-A, double-tagged by one pendant naphthalene between blocks and one anthracene at the end of the PMA block and by 80% of either nontagged PS-PMA or polystyrene-block-poly(ethylene oxide), PS-PEO. The cores of micelles contain pure PS, while the shells contain either PMA-A/PMA or PMA-A/PEO mixed chains. The double tagging by naphthalene and anthracene allows for a nonradiative energy transfer (NRET) study aimed at the estimate of donor-trap distances within one micelle. The fluorometric study suggests that the hydrophobic anthracene tag at the end of shell-forming PMA block tries to avoid the aqueous medium and is buried in the shell, forcing the PMA chain to loop back toward the core. Since the stability of hybrid micellar solutions is guaranteed by favorable interactions of stretched unmodified shell-forming chains (which are in excess in the system) with the aqueous solvent, the reduced entropy of the loop-forming chains does not play such an important role as in micelles with 100% tagging. Hence, we conclude that a higher fraction of the anthracene-tagged chains may return closer to the core-corona interface than in the case of 100% tagged micelles.


Fluorescence Correlation Spectroscopy Using Octadecylrhodamine B as a Specific Micelle-Binding Fluorescent Tag; Light Scattering and Tapping Mode Atomic Force Microscopy Studies of Amphiphilic Water-Soluble Block Copolymer Micelles † , ‡

May 2003

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6 Reads

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33 Citations

Langmuir

Amphiphilic multimolecular block copolymer micelles of polystyrene-block-poly(methacrylic acid) and polystyrene-block-poly(ethylene oxide) were investigated by fluorescence correlation spectroscopy (FCS) in aqueous media using octadecylrhodamine B (ORB) as a micelle-specific probe, together with UV-visible absorption and other fluorescence techniques (steady-state spectroscopy and depolarization and time-resolved fluorescence decay measurements). The aim of the study was to show that the fluorescence techniques alone provide sufficient information on the micellar system, allowing, thus, for the fully conclusive study. Other techniques, such as static and quasi-elastic light scattering and atomic force microscopy were used just for comparison to prove the reliability of the FCS results and estimate their accuracy. The binding kinetics of ORB to micelles in aqueous solutions accompanied by association-dependent changes in UV-vis and fluorescence spectra and the binding equilibrium were also studied because knowledge of them is necessary for the correct interpretation of the FCS results.


Citations (48)


... Nanoparticles used in pharmaceutics are defined as colloidal particles ranging from 10 to 400 nm, in which the active agent is dissolved, loaded, sorbed, encapsulated, or covalently bound. To date, a wide range of carrier nanoparticles of various nature and structure has been developed: dendrimers [6], liposomes [7,8], polymeric NPs [9][10][11], inorganic compounds [12], etc. Biodegradable polymers are of particular interest for the development of drug delivery systems: carriers based on these polymers degrade after performing their function and do not harm the body. There are various natural and synthetic biodegradable polymers, among which lactide based polymers are widely used. ...

Reference:

Nanoformulations of Drugs Based on Biodegradable Lactide Copolymers with Various Molecular Structures and Architectures
Solvents and Self-Organization of Polymers
  • Citing Book
  • January 1996

... 13,17,23,25 Compared to microfluidic techniques, dialysis, which also relies on the principle of solvent interdiffusion, remains the simplest approach to achieve near-equilibrium BC self-assembly without time-scale restrictions. [26][27][28] However, morphology changes of BC structures can be hardly monitored in real time using dialysis bags or tubings unless samples are collected for further analysis. Yet, this approach suffers from a few limitations: i) the polymer concentration cannot be kept constant during regular dialysis, ii) morphology changes occurring over narrow ranges of solvent composition can be overlooked, iii) sampling disrupts dialysis equilibrium, iv) physical aging of collected samples before any analysis is inevitable. ...

Association of polystyrene-poly(methacrylic acid) block copolymers in aqueous media
  • Citing Article
  • April 1991

... Studies using Light Scattering and Atomic Force Spectroscopy on polyelectrolyte complexes of PS-b-PMA and poly (2-vinylpyridine) (P2VP) in 1,4-dioxane-water mixture have shown that the PMA-rich complex is stable at higher pH (>5) and the PVP-rich complex remains stable at a lower value of pH (< 4) [24]. Time-Resolved Fluorescence, Light Scattering, and Atomic Force Microscopy experiments on the hydrophobically modified PS-b-PMA micelles tagged with anthracene near PMA region in dioxane/water mixture have shown that the tagged PMA corona region tend to move towards the core-corona interface as compared to the non-tagged shell, due to the incompatibility of the solvent molecules towards the hydrophobic tagged PMA-anthracene chains [25]. ...

Hybrid Block Copolymer Micelles with Partly Hydrophobically Modified Polyelectrolyte Shells in Polar and Aqueous Media: Experimental Study Using Fluorescence Correlation Spectroscopy, Time-Resolved Fluorescence, Light Scattering, and Atomic Force Microscopy †
  • Citing Conference Paper
  • August 2003

The Journal of Physical Chemistry B

... Therefore, the role of PVP is considered as crucial to form the hollow mesoporous silica spheres. Previous literature (Tsitsilianis et al., 2000, Thibaut et al., 2000 had shown that using a given amount of PVP in a basic aqueous solution, the formation of spherical aggregates is observed. The hydrophilic parts of PVP is at the outer interface with solvent. ...

Polystyrene/Poly(2-vinylpyridine) Heteroarm Star Copolymer Micelles in Aqueous Media and Onion Type Micelles Stabilized by Diblock Copolymers + , ‡
  • Citing Article
  • August 2000

Langmuir

... Otherwise, a wrong dependence of the hydrodynamic radii on polymer concentration will be observed, i.e., a too small radius will be obtained at low polymer concentration [161]. A good example for a suitable dye-polymer combination is octadecyl rhodamine B (ORB) which was found to be a suitable dye for probing the micellization of PS-poly(methyl acrylate) (PMA) block copolymers [164]. In this block copolymer, the ORB binds strongly to the core-shell interface of the PS-PMA micelles with its nonpolar aliphatic tail buried in and partially adsorbed to the PS core. ...

Fluorescence Correlation Spectroscopy Using Octadecylrhodamine B as a Specific Micelle-Binding Fluorescent Tag; Light Scattering and Tapping Mode Atomic Force Microscopy Studies of Amphiphilic Water-Soluble Block Copolymer Micelles † , ‡
  • Citing Article
  • May 2003

Langmuir

... The average molecular weight was controlled by the mole ratio of the catalyst to the monomer to be from 1.3 Â 10 3 to 3.0 Â 10 4 . The number average molecular weight of the low molecular weight nylon 4 (M n , 1.3 Â 10 3 ) was estimated from the 1 H NMR and TOF-MS analyses and the weight average molecular weight of the relatively high molecular weight one (M w , 3.0 Â 10 4 ) was determined by viscometry [28]. Nylon 6 (M w , 3.7 Â 10 4 ) provided by Teijin Co. (Tokyo, Japan) was purified by reprecipitation using 2,2,2-trifluoroethanol (TFE) and acetone as a solvent and a precipitant, respectively. ...

Properties of dilute polypyrrolidone solutions
  • Citing Article
  • January 1974

Collection of Czechoslovak Chemical Communications

... [335,336,340] In purely organic assemblies, homopolymers (HPs), identical or chemically-similar to one of the BCP blocks, have shown capability to swell the core of micelles. [341][342][343][344][345][346] The swelling-induced increase in the micelle core dimeter was found to be related to the relative molecular weight (µ) and the volume fraction (φ) of the HP in relation to its BCP analogue, the compatibility of the solvent for the HP, the degree of chemical incompatibility of the HP and corona forming BCP block (χ HP,A;BCP,B ) and the incompatibility of the two BCP blocks(χ A,B ). [341][342][343][344][345][346] Transitions in the micelle morphology as well as macroscopic phase separation were observed upon increases of µ and φ beyond a critical limit. ...

Solubilization of homopolymers and copolymers by block copolymer micelles in dilute solutions
  • Citing Article
  • June 1981

Die Makromolekulare Chemie

... Konak, et al. 36 report on the diffusion of block copoly- mer micelles through solutions of linear polystyrene, as shown in Figure 18. The block copolymer was a 74 kDa Kraton G-1650 polystyrene-hydrogenated polybutadiene-polystyrene that forms 4.8 MDa 23 nm radius micelles. ...

Diffusion of block copolymer micelles in solutions of a linear polymer
  • Citing Article
  • February 1982

Die Makromolekulare Chemie Rapid Communications

... The morphology of the micelles formed above the critical micelle concentration (CMC) can be spherical, cylindrical, or vesicular depending on the packing parameter of the BCP chains, which is influenced by the attributes of the BCP blocks (i.e., the volume occupied by the core-forming chains, the interfacial area, and the maximum length of the insoluble chains). Asymmetric diblock copolymers can give rise to either hairy (starlike) micelles or crew-cut micelles depending on the relative length of the corona-forming block (long or short, respectively) [24][25][26][27][28]. ...

Block copolymer micelles near critical conditions
  • Citing Article
  • June 1985

Journal of Colloid and Interface Science