Sergei L. Shmakov

Phase processes and energetics of spontaneous change in the dimensions of acetate fibers in nitromethane vapors

The phenomenon of cyclic change (elongation and contraction) in the dimensions of acetate filaments and monofibers in the vapors of nitromethane as a specific solvent is quantitatively described. An algorithm for calculating the energy characteristics of the deformation, including the specific work, is developed. The longitudinal viscosity is estimated according to the deflection of a horizontally stretched sample. It is shown that the stereomeric structure of the polysaccharide is altered in the process of cyclic change in the filament dimensions, as is confirmed by reversal of the sign of specific optical rotation. The resultant data are interpreted in terms of phase (amorphous vitreous versus liquid-crystal states) and conformational transitions.

Optical activity of the anisotropic solutions of cellulose acetates in mesophasogenic solvents

The optical activity of the cholesteric liquid crystalline phases of solutions of cellulose diacetate in nitromethane and dimethylsulfoxide was studied. These systems exhibited optical activity anisotropy (i.e. the value of the specific optical rotation [α] varied with the orientation of the specimen). The contributions of the isotropic component and the anisotropic components of [α] were identified. The harmonic decomposition of the anisotropic component identified the separate contributions from the primary and secondary structures of the polymer and from the supramolecular twisted helicoidal structure of the cholesteric phase.

Algorithm to calculate limiting cumulative particle size distribution functions from turbidimetric data.

An algorithm is offered for finding the range within which cumulative particle size distribution functions can be located in consistency with experimental turbidimetric data at a number of wavelengths. It is based on linear programming and minimization techniques. Several tests were performed. The lower right-hand branch of the corridor was found to locate near the initial distribution function.

Optical-activity anisotropy of ordered phases in cellulose acetates

The optical activity of anisotropic solutions of cellulose diacetate in nitromethane and dimethyl sulfoxide and of diand triacetate films with vitrified ordered structure has been studied. The systems under study are characterized by high specific optical rotation [α], suggesting formation of a cholesteric mesophase. The value of [α] is found to depend on the angle of rotation of the samples relative to the direction of the polarization vector of an incident light beam in the plane perpendicular to this beam (the anisotropy of optical activity). This dependence (indicatrix) shows an irregular pattern and, when plotted in Cartesian coordinates, can be described with a distorted sinusoid. The data on the resolution of indicatrices into harmonic constituents and isolation of contributions due to isotropic components and anisotropic components, each of which is determined by the structural element with the corresponding asymmetry, are analyzed.

Phase Analysis of the Cellulose Triacetate-Nitromethane System

A comprehensive study was made on the cellulose triacetate-nitromethane system to explore its phase separation within ranges 2–25 wt.% and by means of polarization light and electron microscopy, the turbidity spectrum method, differential thermal and X-ray analyses, and rheological techniques. The physical state of the polymer was identified within the phase coexistence boundaries on the phase diagram which included three types of phase separation (amorphous (with a UCST at and wt.%), crystal, and liquid crystal). The boundaries of the regions determining the coexistence of the liquid crystal (LC) and the partly crystal phase were found to be inside the region of amorphous liquid-liquid phase separation. For cellulose ester-solvent systems, this state diagram is the first experimental evidence for the possibility of coexistence of several phases with amorphous, LC, and crystal polymer ordering.