Polymer globule as a nanoreactor

Peculiarities of chemical reactions inside polymer globules with sizes falling in the nanometric range have been theoretically studied. The simplest example of a polymer-catalyzed bimolecular reaction between two low-molecular-weight compounds has been considered to illustrate the advantages of conducting chemical transformations in globular solution of macromolecules. Under theoretical examination of polymer-analogous transformations of polymer molecules, the possibility has been shown of reaction-induced conformational transitions between their coil and globular states. Besides, a pronounced effect has been revealed of the preferential sorption of low-molecular-weight reagents on composition of copolymers formed

New statistical approach to the description of spatial inhomogeneous states in heteropolymer solutions

It is shown that the free energy of polymer systems is a nonlocal functional of the distribution of monomer density, unlike usual low-molecular systems. A general statistical approach is proposed, which takes into account corresponding nonlocal effects for the polymers containing macromolecules of various chemical composition and chemical structure. The phase diagram is set up for solutions of linear heteropolymers, alternation of monomer units in the macromolecules of which obey Markovian statistics. it is shown that a melt of the Markovian multi-block copolymers undergoes a third-order phase transition to superstructure with symmetry of body-centered cubic lattice whose period depends essentially on the parameters of monomer units interactions

Development of a quantitative theory of polycondensation

This review presents the first systematic treatment of the voluminous literature on the theory of polycondensation. Processes for obtaining homo- and copolymers with linear and branched macromolecules are considered. Emphasis is on a thorough discussion of various polycondensation models, and the methods of their solution for the calculation of the statistical characteristics of the chemical structure of polymers. The effects on these characteristics of the process modes for thermodynamically and kinetically controlled regimes of a polycondensation are analyzed in detail

Phase transitions in block copolymers resulting in a discontinuous change of the spatial period of mesophases

The phase behavior of a melt of two-scale multiblock copolymers has been theoretically studied in the framework of the Weak Segregation Limit theory with a two-component order parameter. The existence of a thermodynamically stable mesophase with two scales of the space periodicity has been revealed for a melt of monodisperse nonperiodic heteropolymers. For the first time a discontinuous change with temperature of the spatial period of the mesophases has been predicted.

Molecular Inhomogeneity and Amplitude of Scattering of the Products of Diblock Copolymer Degradation

Expressions are derived for the distributions in size and composition of the macromolecular products of random degradation of diblock copolymers with arbitrary block length distributions. Equations for the calculation of the angular dependence of the static structure factor of these products formed at different depths of degradation are presented. General regularities of the evolution of the spinodal of the polymer melt in the course of this reaction are analyzed. Proceeding from the general theory developed, examples concerning degradation processes of diblock copolymers with particular block length distributions are provided.

Effect of polydispersity on the structure factor of a melt of binary multiblock copolymers with a two-length-scale macromolecular architecture

A theoretical study on the effect of polydispersity of two-length-scale binary multiblock copolymers on the shape of the structure factor is presented. A bifurcation diagram is constructed showing the partition of the parameter space into domains differing in the way in which the homogeneous melt loses thermodynamic stability. When the polydispersity of the two-length-scale multiblock copolymers is high enough the phase diagram may contain a surface of double spinodal points separating regions of trivial and nontrivial spinodal branches. The information about the location of these regions is an indispensable prerequisite for the construction of a phase diagram, because the type of temperature-induced phase transition caused by the loss of thermodynamic stability of the homogeneous state depends on the range of values of the block copolymer parameters

On thermodynamic stability of heteropolymer mesophases formed under weak segregation regime

Conditions of local and global thermodynamic stability of spatially-periodic mesophases formed in an incompressible melt of binary monodisperse copolymers with molecules of arbitrary chemical structure are theoretically scrutinized. For the first time a bifurcation analysis of the Landau free energy in the first harmonic approximation is carried out. Based upon this analysis, feasible scenarios of bifurcation and phase transitions between mesophases of different morphology are discussed. The description of thermodynamic behavior of some systems is presented to exemplify the implementation of the approach proposed

Collaborative Studies of Thermo-Oxidative Degradation of Styrene Isoprene Diblock Copolymer

Mechanisms and dynamics of thermo-oxidative degradation of styrene-co-isoprene (SI) diblock at a temperature above the order–disorder transition temperature, Todt, have been investigated both experimentally and theoretically. The structural development of SI during degradation was monitored by optical microscopy, and the reduction of molecular weight and molecular weight distribution during the degradation was determined by gel permeation chromatography (GPC). The degradation process was modeled in the framework of a kinetic model based on the framework of the Flory principle. The theoretical predictions were compared with the GPC results. Fourier transformed infrared spectroscopy (FTIR) experiment was conducted in situ during the thermo-oxidative degradation of the SI copolymers, to gain further insight into the chemical modification mechanisms, the reduction of unsaturated double bonds and the formation of carbonyl and hydroxyl groups