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Polymer microgels, micrometer-sized cross-linked polymer particles, are considered to be a promising type of advanced materials for a wide range of applications. To enhance the microgels’ applicability, it is essential to incorporate various functional groups into a microparticle polymer network. Yet, the availability of functional groups for the interaction with surroundings depends strongly on the properties of the polymer network and has a great impact on further effective usage. In this theoretical study, we address this question and, with the help of coarse-grained molecular dynamics computer simulations, assess the segmental mobility and accessibility of functional groups bound to polymer network depending on microgel architecture and solvent quality. Additionally, we evaluate the minimum number of functional groups needed to facilitate the hopping mechanism between the functional groups (i.e., charge transfer). As an example of practical implementation of the obtained results, we estimate the optimal network topology for redox-active microgels to provide the maximum charge capacity for the dispersion electrolyte in redox-flow batteries.

We have designed and synthesized two wide bandgap new donor‐acceptor (D‐A) copolymers consisting of the same alkylthiazole‐substituted benzo[1,2‐b;4,5‐b′]dithiophene (BDTTz) donor unit and but different acceptor units, i.e., thiazolo[5,4‐d]thiazole (TTZ) (P122) and 1,3,‐4 thiadiazole (TDz) (P123) and investigated their optical and electrochemical properties. We have employed these copolymers as donor and fullerene (PC71BM) and narrow bandgap non‐fullerene (Y6) as acceptor, to fabricate binary and ternary bulk heterojunction polymer solar cells (PSCs). The overall power conversion efficiency (PCE) of optimized binary bulk heterojunction PSCs based on P122:Y6 and P123:Y6 is 12.60% and 13.16%, respectively. The higher PCE for PSCs based on P123than P122counterparts may be associated with the broader absorption profile of the P123and more charge carrier mobilities than that for the P122active layer. With the incorporation of small amount of PC71BM into either P122:Y6 or P123:Y6 binary blend, the corresponding ternary PSCs showed an overall PCE of 14.89% and 15.52%, respectively, which is higher than the binary counterparts using either Y6 or PC71BM as acceptor. Incorporating the PC71BM in the binary host blend increases the absorption in the 300–500 nm wavelength region, generating more excitons in the active ternary layer and helping to dissociate the excitons into free charge carriers more effectively. The more appropriate nanoscale phase separation in the active ternary layer than the binary counterpart may be one of the reasons for higher PCE.

The phase transitions of poly(N-isopropylacrylamide) (PNIPAM) in water–methanol mixed solutions were studied in detail by high-sensitivity differential scanning calorimetry. From this study, the dependences of the transition temperature, enthalpy, heat capacity increment, and width on the methanol molar fraction (xMeOH) were obtained. The transition temperature passed through a minimum at the methanol molar fraction xMeOH* ∼ 0.35. At xMeOH< xMeOH*, the transition enthalpy decreased quickly with the methanol content and became so small that it could not be measured, even with an increase in the polymer concentration by a hundred times (up to 150 mg mL–1). Furthermore, over this xMeOHrange, the transition heat capacity increment being negative remained practically constant, but the transition width sharply increased. The transition thermograms were quantitatively described by the Okada–Tanaka theory, which takes into account the role of the polymer–solvent interaction cooperativity in the polymer thermoresponsivity. In terms of this approach, it is assumed that over the defined range of methanol content, PNIPAM possesses the cooperative hydro-solvation structure in the form of water–methanol complexes. The energetics of this structure smoothly decreases with the increase in the methanol content up to a complete disappearance of the structure at xMeOH> xMeOH*. In this range of the methanol content, the phase behavior of PNIPAM seems to be dictated by regularities typical of polymer solutions in organic solvents, that is, how the Flory–Huggins parameter depends on temperature.

Changes in the affinity of the swollen and collapsed forms of a thermoresponsive polymer gel for targeted ligands can be directly estimated using a thermodynamic approach based on high-sensitivity differential scanning calorimetry (HS-DSC). For macromolecular ligands (proteins) bound to the gel, this method provides information on changes in their conformational stability, which is of crucial importance for the biological or pharmaceutical activity of the protein. We used HS-DSC for the study of interactions of two widely administrated drugs—gemfibrozil and ibuprofen—and two globular proteins—α-lactalbumin and BSA—with hydrogels of the cross-linked poly(methoxyethylaminophosphazene). The gel collapse resulted in a substantial increase in the gel affinity for the drugs. We obtained quantitative estimations of the affinity of the collapsed gels depending on the gel structure, pH, concentration of NaCl, and phosphate buffer (an inductor of the thermoresponsivity). The gels retained a high affinity for the drugs in the near-physiological conditions (ionic composition and pH). The binding curves of globular proteins to the gels in the swollen and collapsed states were obtained. The different proteins demonstrated the preferential binding to the swollen or collapsed state of the gels, presumably depending on the protein surface hydrophobicity. The proteins bound to the gel subchains retain their native tertiary structure and, therefore, maintain their functionality when immobilized in the polyphosphazene hydrogels.

The interactions between ions and phospholipids are closely associated with the structures and functions of cell membrane. Instead of conventional aqueous systems, we systematically investigated the effects of inorganic ions on the self-assembly of lecithin, a zwitterionic phosphatidylcholine, in cyclohexane. Previous studies have shown that addition of inorganic salts with specific divalent and trivalent cations can transform lecithin organosols into organogels. In this study, we focused on the effect of monovalent alkali halides. Fourier transform infrared spectroscopy was used to demonstrate that the binding strength of the alkali cations with the phosphate of lecithin is in the order Li+> Na+> K+. More importantly, the cation–phosphate interaction is affected by the paired halide anions, and the effect follows the series I–> Br–> Cl–. The salts of stronger interactions with lecithin, including LiCl, LiBr, LiI, and NaI, were found to induce cylindrical micelles sufficiently long to form organogels, while others remain organosols. A mechanism based on the charge density of ions and the enthalpy change of the ion exchange between alkali halides and lecithin headgroup is provided to explain the contrasting interactions and the effectiveness of the salts to induce organogelation.

We investigated energetics of binding of multifunctional pyranine ligands to hydrogels of the cross-linked poly(methoxyethylaminophosphazene) (PMOEAP) from data on the thermotropic volume phase transition of the gels by means of high-sensitivity differential scanning calorimetry. Dependences of the transition temperature, enthalpy, and width on the concentration of pyranines were obtained, and the excess transition free energy as a function of the pyranine concentration was calculated. We found that the affinity of the gels for the pyranine ligands increased very significantly upon the gel collapse. The intrinsic binding constants and free energies of binding of the ligands to the gels in the collapsed state were estimated from the DSC data. They revealed a significant increase in the hydrogel affinity for pyranines proportional to the number of anionic groups in the ligand structure. The affinity of the PMOEAP hydrogels for the multifunctional ligands was not affected by an increase in the cross-linking density of the gels and only slightly reduced by physiological salt concentrations.

Poly(ethylaminophosphazene) (PEAP) in salt-free aqueous solution does not reveal thermoresponsive properties but acquires thermoresponsivity upon addition of various poly(protic acid)s. Energetics of the salt-induced phase separation transition of the PEAP solutions upon heating was investigated by high-sensitivity differential scanning calorimetry at pH 3.5. At low concentrations of poly(carboxylic acid)s (10–100 mM), the transition temperature and enthalpy vary from 90 to 25 °C and from 1.5 to 35 J g–1, respectively, depending on the pKa1and the apparent hydrophobicity of the acids. Dependences of the transition parameters (Tt, Δth, and Δtcp) on the citrate buffer concentration were obtained. The binding curve of citrate anions to PEAP was derived. High concentrations of sulfate anions (0.1–0.8 M) induced a marginal phase transition at high temperatures. A mechanism of the PEAP thermoresponsivity is proposed. The Okado–Tanaka model for cooperative hydration of macromolecules is used to quantitatively describe the energetics of the thermoresponsive behavior of PEAP.

In this paper, for the first time, we report the results of molecular dynamics simulation of the electrode/electrolyte interface of a Li–O2cathode under potentials close to experimental values in 1 M dimethyl sulfoxide (DMSO) solution of LiPF6salt. Electric potential profiles, solvent structuring near the electrode surface, and salt ion distributions are presented and discussed here as well as potentials of mean force (PMFs) of oxygen and its reduction products. The latter would be of a great use for future theoretical studies of reaction kinetics as PMF is essentially the work term required for reaction rate constant estimations. At the electrode/electrolyte interface under realistic potentials, oxygen anions are effectively pushed out of the reaction layer, making the second reduction of superoxide anion hardly probable. This indicates that the main cause of the electrode surface passivation should be lithium superoxide presence near the electrode surface. The way to suppress the passivation is to shift the equilibrium Ȯ2–+ Li+⇌ LiO2to the side of separately solvated ions, for example, by using solvents resulting in lower free energy of the ions. This conclusion is in agreement with the hypothesis stating that high donor number solvents lead to dominant solution Li2O2growth and significantly higher cell discharge capacities.

Two donor–acceptor (D–A) backbone copolymers with different fused ring acceptors, i.e., dithieno [2,3‐e:3′,2′‐g]isoindole‐7,9(8 H)‐dione (DTID) and dithieno[3′,2′:5,6;2″,3″:7,8]naphtho[2,3‐d]imidazol‐9(10 H)‐one (DTNID) and same benzo[1,2‐b:4,5‐b′]dithiophene with alkylated aromatic side as side chains (BDTT) donor, denoted as P133and P135are synthesized and used as donor along with narrow bandgap nonfullerene Y6 acceptor for the preparation of polymer solar cells (PSCs). The dielectric constant of P135:Y6 is higher than that of P133:Y6 due to the strong electron deficient ability of DTNID compared to DTID, which fostered exciton dissociation and charge transport, constrained charge recombination, and ultimately boosted the power conversion efficiency of P135:Y6 to 15.11%, which is higher than P133:Y6 (10.24%). Therefore, these investigations confirm the pronounced potential of fused ring DTNID as an acceptor unit for emerging D–A copolymers for PSCs with high efficiency. The power conversion efficiency for P135:Y6 (15.11%) is higher than that for P133:Y6 (10.24%), which is attributed to the efficient charge separation and transport due to the high dielectric constant of the former blend, owing to the reduced exciton binding energy due to the two polar carbonyl groups in P135 donor–acceptor copolymer.

We present results of an experimental study concentrated on performance optimization of highly sensitive Pb $_{1-x}$Sn $_x$Te(In) terahertz photodetectors perspective for applications in the terahertz astronomy. The optimization was reached trough variation of the regime of persistent photoconductivity quenching by radio-frequency pulses. It is demonstrated that the quenching effectiveness rises rapidly with decreasing the radio-frequency in a quenching pulse. In certain regimes, the quenching boosts the photoresponse after the end of the radio-frequency pulse. Possible mechanisms of the radio-frequency quenching of the terahertz persistent photoconductivity in Pb$_{1-x}$ Sn$_x$Te(In) are discussed.

Two novel regular terpolymers that are of D-A1–D-A2 type and contain benzothiadiazole and 2,5-dibromo-8-dodecanoylbenzo[1,2-b:3,4-b′:5,6-d″]trithiophene (P1) or 2,8-dibromo-5-dodecanoylbenzene[1,2-b:3,4-b′:5,6-d″]trithiophene (P2) acceptor units with the same thiophene donor were synthesized through Stille coupling, and their optical and electrochemical properties were investigated. The highest occupied molecular orbital (HOMO) and lowest unoccupied (LUMO) molecular orbital energy levels of these terpolymers indicate that there is sufficient LUMO offset with PCBM for efficient exciton dissociation, and their deeper HOMO levels ensure the high open-circuit voltage for the resultant bulk heterojunction solar cells. Measurements on the solar cell devices also confirm that compared to those based on P2the devices based on P1possess a higher short-circuit photocurrent (Jsc) as well as a higher fill factor (FF), which is attributed to the lower bandgap and higher hole mobility for P1, whereas the Vocis higher for the devices that are based on P2, which may be a result of P2 having a lower HOMO energy level than P1. The optimized polymer solar cells fabricated using P1:PC71BM (DIO/CF) and P2:PC71BM (CF/DIO) for the active layers showed a PCE of 7.19% and 6.34%, respectively. Atomic force microscopy (AFM) images of P1:PC71BM blend films show that they exhibit more suitable morphology with favorable interpenetrating networks, which favors high Jscand FF. Moreover, P1exhibits a more crystalline nature than P2that also favors the charge transport. This may be a result of better molecular packing, more distinct phase separation of the blended films, as well as a reduction of charge recombination.

We discuss the solution properties of polymers with a highly anisotropic rigidity which bend rather freely in a plane (the plane of main flexibility) and are extremely rigid in the direction perpendicular to this plane. Examples of these polymers are the ladder polymers recently synthesized or living polymers formed by the aggregation of peptide rodlike fragments. These polymers have a much higher out of plane persistence length l2than their in-plane persistence length l. In the first paper of this series, we mostly inverstigate the conformation of single chains in solution (at extremely low concentrations). The conformation of an isolated chain with a highly anisotropic rigidity essentially depends on the dimensionless parameter Ω= l2d2l-3where d is the chain diameter. For small values of Ω, (l2∼l), the chain behaves as a standard semiflexible chain with isotropic rigidity. For large values of $\Omega, (\Omega \gtrsim 1)$, the chain adopts a one-dimensional rodlike conformation at length scales smaller than l, an anisotropic disc-like conformation at intermediate scales (corresponding to a contour length L such that $l\lesssim L \lesssim l_2$) and a three-dimensional swollen coil conformation at larger length scale. In the intermediate range of $\Omega, l^2/d^2\lesssim \Omega\lesssim 1$, the same three regimes are expected but the excluded volume interactions do not play any role in the disc-like regime. At the end of the paper we discuss qualitatively the possible liquid crystalline phases (with nematic or smectic symmetry) which can emerge in these solutions at higher concentration.

The thermodynamics of the bicomponent melts of linear chains A and unknotted unentangled closed chains B (trivial rings) is considered within the framework of the usual Flory approach. It is shown that such melts exhibit a compatibility enhancement in comparison with the corresponding melts of linear chains. The reason for such effect is due to the topological entropy gain of mixing of A- and B-chains: if B-chains are unentangled since the A-chains play the role of a “diluent” softening the topological restrictions imposed on the B-chains. This result is in agreement with recent experimental findings of McKnight et al.

The microphase separation transition in the weakly charged polyelectrolyte gels immersed in poor solvent and undergoing collapse transition is studied in the weak crystallization approximation. The chain connectivity in the gel is taken into account viaintroducing “polarization" term first proposed by de Gennes. It is shown that in this case the gel can undergo multistage jump–like collapse where the intermediate states can have regular microstructures of different symmetry. The availability of numerous metastable states in the collapse region may lead to the pronounced hysteresis effects. These results are compared with some of the recent experimental findings.

A microscopic theory of the mixtures of polymer chains and colloidal particles immersed in a common solvent is developed on the basis of the RISM integral equation technique. The obtained general equations enable the calculation of the correlation functions and thermodynamic characteristics of the system at an arbitrary ratio of the components. The theory is used for a comprehensive study of interaction of small spherical particles with flexible polymer chains in the regimes of weak and strong adsorption of the macromolecules on the surface of the particles. The temperature and concentration regions characterized by different effect of the polymer on stability of the colloidal dispersion are determined. The corresponding temperature–concentration diagrams of state are constructed.

The viscosity of a fluid can be measured by observing the motion of a probe sphere (or ball) in a centrifuge tube filled with this fluid. The hydrodynamic behavior of the probe ball moving in the centrifuge tube has been solved theoretically. We have got the universal relationship (for balls of a given material and size in a given tube) between the terminal ball velocity, the fluid viscosity and the centrifuge acceleration using the only adjustable parameter — the rotational friction coefficient between the ball and the tube. The rotation of the centrifuge tube in the horizontal plane induces an inertia force which is counterbalanced by the friction force acting on the ball. As a result, the ball moves along the tube with some characteristic speed, which is a measure of the viscosity of the fluid. This speed was calculated in the lubrication approximation. The gravitational acceleration causes the ball to move very close to the bottom of the centrifuge tube. In this situation, the gravity is balanced by a “levitation” force introduced and calculated in the present paper. The origin of this force is the formation of the “bubble” behind and below the moving ball. The theoretical development on the terminal velocity for the ball moving very near the bottom of the horizontal centrifuge tube is tested by using a specially designed centrifuge for two types of balls and a wide set of viscosity standards. Excellent agreement between theory and experiment suggests that we have developed a new approach to measure high viscosities of fluids at low shear rates which might be especially useful for the investigation of polymer melts.

We report on the influence of oxidation on features of surface electron states in PbSe films—materials belonging to the family of topological crystalline insulators Pb $_{1-x}$Sn$_x$Se. These states are detected through observation of the photoelectromagnetic effect induced by terahertz laser pulses. It is demonstrated that highly conductive surface electron states in PbSe are inherent to the semiconductor itself and are not related to the material oxidation. This allows excluding surface states induced by oxidation as a reason for high surface conductivity in topological crystalline insulators based on Pb$_{1-x}$ Sn$_x$ Se.

This paper reviews unusual photoelectric effects observed in doped narrow-gap PbTe-based semiconductors exposed to intense terahertz laser pulses. It is shown that in some cases these effects are due to those (nontrivial) local electronic states that, unlike ordinary, spectrally defined impurity states, are linked to the quasi-Fermi level, whose position can be varied by changing the degree of photoexcitation.

Self-consistent field theory and dissipative particle dynamics simulations are used to demonstrate the controlled positioning and alignment of cylindrical domains by chemical surface patterns in an asymmetric slit. Self-assembly of the copolymer melt is simulated near dense and sparse surface patterns, both with one and two characteristic length scales. In particular, we compare the effect of a hexagonal pattern, sparse rectangular pattern, and triangle pattern. The parallel alignment of microdomains between preferentially attractive homogeneous surfaces is shown to transform into the stable perpendicular hexagonal phase in the case of the substrate patterns, which commensurate with the hexagonal morphology in the bulk. For the sparse rectangular pattern, when two different length scales of interactions are involved, and for the sparse hexagonal pattern, we observe that the self-assembly of diblocks multiplies the density of the surface patterns by a factor of 2 and 4, respectively. A 2-fold resolution enhancement was found for sparse triangle pattern with two characteristic length scales. The analysis of the circularly averaged structure factor allowed us to distinguish the structure orientation in a film. Additional peak in the region of small lateral wave numbers is attributed to undulational deformations of cylinder domains under preferable film boundaries. This theoretical work serves to rationalize modern nanolithographic fabrication of high-spatial-frequency arrays using lower-spatial-frequency templates.

We report herein the synthesis of a novel type of hybrid compound that consists of a poly(ethylene oxide) (PEO) functionalized β-sheet peptide sequence covalently linked to an alkylated quaterthiophene moiety. Compounds of this class are highly promising for technological applications because their self-assembly and stimuli-responsive behavior, which is mainly caused by the peptide moieties, combined with the potential semiconducting properties of oligothiophenes provides unprecedented opportunities for the design of advanced materials at the nanoscale in such areas as, for example, organic electronics and sensor design for chemical and biomedical applications. The compound presented herein is experimentally shown to form stable fibrillar aggregates that are visualized by both transmission electron and atomic force microscopy. We developed a theoretical methodology to study the possible intermolecular arrangements and their characteristic features with the help of all-atom MD simulations, while simultaneously incorporating available experimental data into the model. Large-scale atomistic simulations of several fibrillar aggregates with different molecular arrangements were performed. The results of the simulations are compared with experimental data, which leads to the proposition of a likely model for the arrangement of the individual molecules within the observed aggregates.

The conformational behavior of a single AB block copolymer is studied by Monte Carlo simulation. The A‐A and A‐B interactions have the character of excluded volume interactions while the B units attract each other; the attractive B blocks can move along the chain. The collapse transition of the chain with increasing attraction between the B units is analyzed. Intrachain separation of the A and B units takes place in the course of the chain collapse with the formation of “globule with a tail” conformations. The globule is formed by the attractive moving B blocks while the tail consists of the swollen A segments. The model of AB block copolymer with moving B blocks can describe the behavior of interpolymer complexes between a long macromolecule and shorter polymer chains.

Novel magnetorheological elastomers MRE based on a highly elastic silicone rubber filled with carbonyl iron magnetic particles of 3–5 and 3–50 µm are synthesized. The effect of an external homogeneous magnetic field on the viscoelastic properties of these materials is studied by dynamic experiments shear oscillations on a rheometer. It is shown that the magnetic response of the MRE increases with a decrease of the strain. At 1 deformation both the storage and loss moduli of the new MRE demonstrate a giant response to the magnetic field, namely, an increase of more than two orders of magnitude in both moduli in a field of 300 mT is observed. In addition, these new MREs show a twofold increase of the damping ratio, which is important for their application as tunable vibration absorbers.

This review highlights recent advances achieved by different groups with various molecular simulation approaches for the prediction and fine‐tuning of the supramolecular organization of thiophene derivatives, oligo‐ and polythiophenes. The focus is on functionalized oligo‐ and polythiophenes, including bio‐inspired thiophene/peptide copolymers (“molecular chimeras”). The subject matter of the article is divided up into subsections covering electronic and structural properties of single molecules, solution and solid‐state self‐assembly, amorphous polythiophene and polymer blends, thiophene‐based nanomechanical devices, self‐organization on substrates and applications. A number of examples are used to provide experimental data with which to compare the theoretical predictions.

We deposited single individual macromolecules of chitosan directly from their solutions in supercritical carbon dioxide onto a substrate surface and applied SFM method to analyze the macromolecular conformation. By means of image processing of many different SFMcontours of the visualized individual macromolecules, we determined the scaling exponent ν, which describes the correlation between mean square endtoend distances and contour lengths of the adsorbed macromolecules. It was revealed, that the macromolecules, deposited from scCO2and visualized by SFM, tended to adopt rather extended conformation. The scaling exponent νwas found to be in range of 0.78–0.8, which was slightly above the 34 value, corresponding to 2D selfavoiding walk statistics. Good adhesion of chitosan coatings directly deposited from scCO2is expected.

Summary: In this work, we discuss a simple evolutionary algorithm that introduces a “selection pressure” under which two‐letter (AB) copolymer sequences can mutate and transform into the sequences tuned to microphase separation transition (MIST). In particular, we are interested in determining how a sequence of A and B units should be organized in order to reach maximum length scale for MIST at a given AB composition. It is found that such sequences are similar to those known for tapered or gradient copolymers exhibiting strong composition inhomogeneity along their chain. The problems of the evolution of copolymer sequences are considered from the viewpoint of emerging of information complexity in the sequences in the course of this evolution.

Summary:We studied coil‐globule transitions in stiff‐chain amphiphilic macromolecules via computer modeling and constructed phase diagrams for such molecules in terms of solvent quality and persistence length. We showed that the shape of the phase diagram essentially depends on the macromolecule degree of polymerization. Relatively short amphiphilic molecules always form a spherical globule in a poor solvent, and the coil‐globule transition includes one or two intermediate conformations, depending on the chain's stiffness. These are a disk‐like globule in case of high enough Kuhn segment length, and a pearl necklace‐like structure of spherical micelles and a disk‐like globule in case of relatively flexible chains. The phase diagram of a long stiff amphiphilic chain was found to be more complex still. Thus three specific regions can be distinguished in the poor solvent region, depending on the chain stiffness. These correspond to a cylindrical globule without any specific backbone ordering, a cylindrical globule containing blobs with collagen‐like ordering of the chain, and co‐existence of collagen‐like and toroidal globules. In the intermediate transition region in this case, apart from the pearl necklace‐like conformations with spherical micelles, necklace conformations can be also observed where the polymeric chain has collagen‐like ordering within each bead.

We propose a model of molecular motor based on diblock copolymer strongly adsorbed on a patterned surface. One of the blocks of the copolymer is modeled as field responsive. It is shown that time‐periodic collapse‐readsorption of the responsive block leads to the directed motion (reptation) of the molecule along the “track” provided by the surface pattern. Both the Langevin dynamics (LD) technique of computer simulation for the bead‐spring model and numerical solution of the Newton equations of a simplified (toy) model of the copolymer are used. The physical reason of directionality of the motion is shown to be an anisotropy of the friction of the molecule with the surface.

We synthesised P4VP bromides with octyl and dodecyl pendant groups; the bromide anions in these polymer salts were further substituted with dodecylsulfate or bis(2-ethylhexylsuccinate) anions. Direct SFM visualisation of the original P4VP chains, of the macromolecular salts and of their complexes, showed that the attachment of the pendant groups and especially the complexation with the surfactants promotes stretching of the macromolecules while adsorbing on mica substrate. On the other hand, viscosimetry showed that in solution (chloroform) the comb‐like chains and their complexes with dodecylsulfate had more compact conformations than those of the original P4VP. The scaling exponents describing the correlation between the contour length and the end‐to‐end distance of the adsorbed macromolecules were found to be ca. 3/4, which is indicative of 2D self‐avoiding walk statistics.

The works on mathematical modeling of interfacial polycondensation are reviewed over the period since 1970s up to now. Attention is primarily paid to the techniques of local and macrokinetic modeling. Two approaches to the theoretical description of polycondensation have been formed up to date. The first one is based on analytical or semianalytical solution of differential balance equations using the stationary mass transfer approximation. The second one consists in numerical solution of the system of reaction–diffusion equations for the diffusion boundary layer of the reaction phase. The advantages and drawbacks of these approaches, specific features of their realization, basic results, as well as ways of combining these methods are discussed. A possibility of building a general model of interfacial polycondensation as a hierarchical combination of kinetic, local, and macrokinetic models is shown. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2698–2724, 2006

Summary:Poly(4‐vinylpyridinium) bromides containing octyl and dodecyl pendant groups were synthesized. Bromide anions in these polymer salts were substituted with dodecylsulfate and bis(2‐ethylhexylsuccinate) anions using ion‐exchange reactions. Initially, P4VP and its derivatives loaded with hydrophobic groups were deposited on a mica surface from diluted solutions in chloroform for visualization. Images of single adsorbed macromolecules were obtained using scanning force microscopy. Original P4VP chains form partially compacted self‐intersecting coils. Loading the polymer chains with large hydrophobic groups and especially the increase in the number of alkyl tails (see Figure) per monomer unit of the polymer chain leads to the stretching of the coils, and the comb‐like macromolecules adopt more and more extended self‐avoiding 2D conformations when deposited on the substrate.

Summary:We have performed analysis of protein sequences treating them as texts written in a “protein” language. We have shown that repeating patterns (words) of various lengths can be identified in these sequences. It was found that the maximum word lengths are different for proteins belonging to different classes; therefore, the corresponding values can be used to characterize the protein type. The suggested technique was first applied to analyze (decompose into words) normal (literature) texts written as a gapless symbolic sequence without spaces and punctuation marks. The tests using fiction, scientific, and popular scientific English texts proved the relative efficiency of the technique.

The free-radical copolymerization of N-vinylcaprolactam and N-vinylimidazole (at an initial comonomer ratio of 85: 15, mol/mol) initiated by a persulfate-tertiary amine redox system in 10% aqueous DMSO at 25 and 65°C (at temperatures below and above the temperature of phase separation in the reaction system, respectively) yielded macromolecular products that were subsequently separated into thermally precipitating and nonprecipitating fractions. Investigations of these fractions by capillary viscometry, static and dynamic laser light scattering, and high-sensitivity DSC showed that macromolecules of both types of copolymers are strongly associated in aqueous solutions. Upon heating of solutions of thermally nonprecipitating fractions, additional aggregation takes place and this phenomenon is accompanied by a decrease in the size of particles without loss in their solubility until at least 70°C is reached. As for the set of properties exhibited in aqueous solutions, the thermally nonprecipitating fraction of the copolymer synthesized at 65°C may be assigned to protein-like macromolecules.