Ya.S. Freidzon

Thermotropic liquid crystalline polymers—19. Peculiarities of the liquid crystalline structure of cholesterol-containing polymers☆

Abstract Phase transitions and structure of cholesterol-containing polymers, poly(cholesteryl-ω-acryloyloxyalkanoates) and poly(cholesteryl-ω-methacryloyloxyalkanoates), were examined by differential scanning calorimetry. X-ray studies and polarization microscopy. The polymers are shown to form smectic and cholesteric mesophases. Models for the packing of macromolecules in the liquid crystalline state are suggested. The cholesteric structure of the polymers is characterized by layer ordering in the arrangement of mesogenic groups. The cholesteric mesophase of the polymers was found to exhibit selective light reflection in the u.v.-region and circular dichroism.

Thermotropic liquid crystalline polymers—22. Optical properties and structure of some cholesteric copolymers

Abstract Copolymers of the nematogenic monomer, p -(ϵ-acryloyloxycaproyloxy)- p ′-methoxyphenylbenzoate, with various cholesterol-containing monomers were synthesized. The copolymers were shown to form mesophases of the cholesteric type. The dependence of the selective reflection of light on copolymer composition was studied. The copolymers with low content of chiral groups form monochromic cholesteric mesophases, with the cholesteric helix pitch being independent of temperature; the helix for copolymers with high content of chiral groups increases its pitch with increase of temperature.

Thermotropic liquid-crystalline polymers XXIII. Peculiarities of uniaxial orientation of comb-like liquid-crystalline polymers under mechanical stress

Abstract The structure of oriented samples of liquid-crystalline side-chain polymers has been studied by X-ray diffraction. The arrangement of the different fragments of the macromolecules is shown to be dependent on the mesophase type of the initial melt. The orientation of the nematic melt leads to parallel alignment of mesogenic groups along the fibre axis. In the smectic melt, the smectic layers are arranged along the fibre axis with the mesogenic groups normal (SA and SB) or tilted (SC and SF) to it.

Specific features of liquid-crystalline comb-like polymers with mesogenic groups

Abstract The results of structural investigation of the new type of the liquid-crystalline thermotropic methacrylic polymers are discussed. These polymers contain mesogenic groups as models for cholesteric, nematic and smectic types of low-molecular liquid crystals. The groups are attached to the backbone through methylene bridges of various lengths. The polymers of the first group have amorphous structure; the polymers of the second group are characterized by liquid crystalline structure and those of the third group can exist in both crystalline and liquid-crystalline states, manifesting properties of enantiotropic liquid crystals. The temperatures and heats of phase transitions have been determined. It is shown that the ability to realize the liquid-crystalline state of comb-like polymers with mesogenic groups depends on and is determined by the proceess of ordering of these groups.

Liquid-crystalline state of cholesterol-containing monomers

Abstract A series of cholesterol-containing monomers was synthesized: cholesteryl esters of N-acryloyl-ω-aminocarboxylic acids, N-methacryloyl-ω-aminocarboxylic acids, ω-acryloyloxycarboxylic acids and ω-methacryloyloxycarboxylic acids. The mesomorphic properties, temperatures and heats of transitions of monomers were investigated in comparison with the cholesteryl alkanoates. The temperature range of cholesteric mesophase of monomers—derivatives of oxycarboxylic acids was shown to be wide. Such monomers can be used in thermographic composites and for synthesis of the liquid-crystalline polymers.

Structure and properties of liquid crystal polymers containing cholesterol

Abstract An investigation has been made of the structure and properties of cholesteryl esters of poly-N-methacryloyl-ω-aminocarboxylic acids differing in the length, n , of the pendant alkyl substituent (PChMAA- n ) and copolymers of ChMAA- n with n-alkylacrylates and n-alkylmethacrylates. The effect of the length of the methylene chain linking the cholesterol groups with the main chain has been considered, as well as the frequency with which the cholesterol groups are positioned in the structure and the properties of the polymers under investigation. It has been shown that, when the number of methylene links in the pendant alkyl radical, n , is greater or equal to 5, the polymers form a liquid crystal (LC) phase in the glassy, highly elestic and viscous low conditions. Schemes for the packing of the macromolecules of the polymers containing cholesterol in the LC condition are put forward.

Features of layer orderliness of cholesterol-containing polymers☆

Abstract The structure of cholesterol-containing homopolymers in the smectic and cholesteric mesophases has been studied by the X-ray method. It is shown that the polymers form a smectic mesophase of the S A -type in which the side mesogenic groups are arranged perpendicular to the planes of the smectic layers with the co-existence of two types of packing-with antiparallel disposition of the mesogenic groups and with overlap of the terminal aliphatic substituents. In the cholesteric mesophase layer order in the arrangement of the mesogenic groups exists. A scheme of packing of the macromolecules in the cholesteric mesophase is proposed.

The synthesis and structural investigation of polymers and copolymers of the cholesterol ester of methacryloyl-ω-hydroxypentadecanoic acid☆

Abstract The results of the synthesis and structural analysis and study of certain physicochemical properties of the cholesterol ester of methacryloyl-ω-hydroxypentadecanoic acid are presented, as well as those of the polymers and copolymers of the latter monomer with butyl methacrylate and butyl acrylate. The transition temperatures have been identified and the polymer and copolymer structures investigated. The fact of the formation of a liquid crystalline structure in the glass-like, high elastic and viscous flow states is proved. Boundary conditions have been found under which the liquid-crystalline state is realized for the copolymers, and a study has been made of the effect of the conditions of formation of films of the homopolymers on their ability to display optical anisotropy.

Structure formation in liquid crystalline polymers containing cholesterol

Abstract Polarization luminescence, spectropolarimetry, X-ray diffractometry, electron microscopy and optical microscopy were used to examine structure formation in polymers containing cholesterol and homopolymers of cholesteric ester of N-methacryloyl-ω-amino lauric acid and its copolymers with butylmethacrylate of different compositions. It was shown that in solutions of these polymers in non-polar solvents near the point of phase separation conformation transition is observed which is accompanied by the formation of a perfect intramolecular structure. A comparison of the structure and properties of polymer films, obtained from different solvents suggests that the formation of an intramolecular structure is a requisite condition of the liquid crystalline state in films.

Features of molecular mobility in solutions of comb-like polymers with mesogenic groups in their side chains

Abstract The molecular mobility of cholesteryk ether of poly(methacryol-ω-hydroxyundecanoic acid) in dilute solution was studied by the dielectric method. The polymer exhibits cooperative internal motion with unusually high correlation times, similar to those previously observed in solutions of polymers with diphenycyanide groups in their side chains. The effects of the structure of the side chain, of polymer molecular mass and of the thermodynamic quality of solvent on the parameters of the relaxation process were studied. In solutions of this type of polymers, elements of structural order are assumed to exist.