Reversible temperature-induced transformations of poly(N-ethyl-4-vinylpyridinium) complexes with dodecyl sulfate in aqueous salt solutions

Supramolecular organization of complexes formed by poly(N-ethyl-4-vinylpyridinium bromide) and sodium dodecylsulfate in aqueous salt solutions was studied as a function of temperature and concentration of the complexes. It was shown that a decrease in temperature and/or concentration of complexes led to their reversible disaggregation into a molecularly dispersed (“unipolymer”) state. The ratio between the components in complex particles remained unchanged in this case. It was first found that phase separation in aqueous solutions of the complexes upon temperature elevation is accompanied by the precipitation of a nonstoichiometric complex.     

EPR spin probe and spin label studies of some low molecular and polymer micelles

The rotational mobility of spin probes of different shape and size in low molecular and polymer micelles has been studied. Several probes having nitroxide fragment localized either in the vicinity of micelle interface or in the hydrocarbon core have been used. Upon increasing the number of carbon atoms in hydrocarbon chain of detergent from 7 to 13 (sodium alkyl sulfate micelles) or from 12 to 16 (alkyltrimethylammonium bromide micelles) the rotational mobility of spin probes is decreased by the factor 1.5–2.0. The spin probe rotational mobility in polymer micelles (the complexes of alkyltrimethylammonium bromides and polymethacrylic or polyacrylic acids) is less than mobility in free micelles of the same surfactants. The study of EPR-spectra of spin labeled polymethacrylic acid (PMA) indicated that formation of water soluble complexes of polymer and alkyltrimethylammonium bromides in alkaline solutions (pH 9) does not affect the polymer segmental mobility. On the other hand, the polymer complexes formation in slightly acidic water solution (pH 6) breaks down the compact PMA conformation, thus increasing the polymer segmental mobility. Possible structures of polymer micelles are discussed.     

Some EPR spin probe and spin label studies of polymer systems

The application of EPR spin probe and spin label technique for solving the two problems of polymer physical chemistry is considered. The first problem is the determination of conformational state and chain sizes in amorphous solid polymers. This determination is based on the analysis of the intramolecular dipolar broadening of EPR spectra of spin labelled macromolecules in glassy solvents or in the bulk of unlabeled polymers at 77 K. The second problem is the determination of molecular mobility and structure of two polymer colloid systems: (a) the complex of colloidal silica and synthetic polycation macromolecule and (b) polymer-surfactant micellar organized systme.     

Higher order symmetrizer and application to an unusual transport equation

We study a class of stationary transport equation with nonlocal low-order tems We obtain the existence and uniqueness of a solution in sobolev spaces     

求解复杂湍流的非线性涡黏性系数模型和代数应力模型

非线性涡黏性系数模型和代数应力模型联系了线性涡黏性系数湍流模型和完整的微分 雷诺应力模型.随着它们受到日益关注,其形式也越来越多样化.本篇综述的目的是对这些模 型加以总结并比较它们之间的共同点及不同之处,指出它们与完整微分雷诺应力模型之间的 关系,以及相对于线性涡黏性系数模型而言它们在预报流场上所具有的优势.     

Complexing of Polymethacrylic Acid Esters with ZnCl2 in Solutions of Their Monomers

Abstract

The processes of ZnCl₂ selective sorption by macromolecules of polymethyl methacrylate and polybutyl methacrylate in binary mixtures with ZnCl₂ have been studied using light scattering and equilibrium dialysis methods. It has been shown that to a certain concentration of ZnCl₂, its average concentration in the volume of macro-molecular coils is equal to that of the complexing agent in the solution, i.e., the parameter of the selective sorption β = 0. However, for the system PBMA-BMA-ZnCl₂ with increasing [ZnCl₂], a negative value of β is observed. After the “threshold” concentration of [ZnCl₂]: methyl methacrylate = 0.08, butyl methacrylate = 0.15, an increase in the selective sorption of ZnCl₂ concentrations is found. The interaction of ZnCl₂ with macromolecules of polymethyl methacrylate and polybutyl methacrylate is accompanied by a change in the steric parameter and in the thermodynamic quality of the solvent. A probable mechanism of ZnCl₂ interaction with polymer coils is discussed.

Many reactions involving the participation of macromolecules occur in multicomponent solutions, and the distribution of solvent components, within and outside of a polymer coil, can considerably affect the process features. Hence, the behavior of macromolecule in binary solvents is important in the study of the physical chemistry of polymer solutions. Radical polymerization in the presence of complexing agents (CA), where the latter considerably influence the kinetic features of the reaction [1, 2], is an example of a process in which these effects should be manifested. In particular, in methyl methacrylate (MMA) polymerization an increase in CA (ZnCl₂) concentration results in an increase in the chain propagation constant, influences the composition of copolymers, and can cause a sharp drop in the bimolecular termination constant. It has been assumed that the latter is connected with the specific interaction of CA molecules with the propagating macroradicals [3, 4].

This paper reports on studies of the behavior of methacrylic polymers in the binary solvent monomer- ZnCl₂. These studies permitted us to simulate the polymerizing system and to learn the effects of complexation on the equilibrium flexibility of a macromolecule. These data are also of independent interest because they permitted us to elucidate the specific characteristics of complexing with the participation of macromolecular ligands.     

Molecular organization and dynamics of micellar phase of polyelectrolyte-surfactant complexes: ESR spin probe study

Molecular dynamics and organization of the micellar phase of complexes of linear polyelectrolytes with ionogenic and non-ionogenic surfactants was studied by the ESR spin probe method. Complexes of polyacrylic acid (PAA) and sodium polystyrenesulfonate (PSS) with alkyltrimethylammonium bromides (ATAB), as well as complexes of poly-N,N'-dimethyldiallylammonium chloride (PDACL) with sodium dodecylsulfate (SDS) were studied. The micellar phase of such complexes is highly organized molecular system, molecular ordering of which near the polymeric chain is much higher than in the 'center' of the micelle, it depends on the polymer-detergent interaction, flexibility of polymeric chain and length of carbonic part of the detergent molecule. Complexes of polymethacrylic acid (PMAA) with non-ionic detergent (dodecyl-substituted polyethyleneglycol), show that the local mobility of surfactant in such complexes is significantly lower than in 'free' micelles and depends on the number of micellar particles participating in formation of complexes.     

Untersuchung der wasserl?slichen Polyelektrolytkomplexe auf der Basis von Natriumpolvacrylat und 5,6-Ionenbromid

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