Dependence of the transitional properties of polystyrene-based side-chain liquid-crystalline polymers on the chemical nature of the mesogenic group (original) (raw)
Related papers
Journal of Polymer Science Part A: Polymer Chemistry, 1989
Copolymerization of monomers containing the disiloxane unit in the spacer component and linear triple-core mesogens with comonomers containing linear double-core mesogens, or laterally attached triple-core mesogens was carried out radically. The effect of copolymer composition and monomer structure on the mesomorphic properties of the obtained copolymers was investigated in detail. The copolymers with a comonomer content up to 50 mol-%, exhibit an enantiotropic nematic phase, whereas the parent homopolymers containing triple-core mesogens exhibit a smectic phase. The copolymer containing more than 50 mol-To of the comonomer shows no mesophase. The isotropization temperature of the copolymers decreases with increasing comonomer content. However, the glass transition temperature is almost unchanged upon introduction of the comonomer unit. In case of copolymers containing laterally attached mesogens, a smectic phase was observed below the temperature range of the nematic phase. Consequently, the mesophase and the temperature range of the liquid-crystalline state can be controlled by the introduction of the comonomer unit whose parent homopolymer does not exhibit any mesophase.
Liquid Crystals, 2008
Side-chain liquid-crystalline copolymers containing both a mesogenic (carbazolylmethy1ene)aniline group as the electron donor and a mesogenic (4'-nitrobenzylidene)aniline group as the electron acceptor with alkylene spacers of different lengths were prepared. The thermal stabilization and the induction of the smectic phases were observed for the copolymers containing spacers with similar lengths. For example, the copolymer containing both a hexamethylene spacer in the carbazolyl group and a trimethylene spacer in the nitrophenyl group exhibited a smectic phase from 77 to 191 "C, though the smectic phase did not appear in both homopolymers. On the other hand, these tendencies were not seen for the copolymers with spacers of a large variation in the length, i.e., undecamethylene and ethylene spacers. Thus, it is revealed that the thermal stability and the induction of the smectic phases in the copolymers are influenced to a large extent by the degree of overlapping between the mesogenic side groups through the electron donor-acceptor interaction.
Synthesis and structure of liquid-crystalline side-chain polymers
Pure and Applied Chemistry, 2000
The synthesis, structure and some properties of therrn6tropic liquid crystalline polymers with side xnesogenic groups are discussed. Approaches towards the synthesis of such systems are presented, as well as the data revealing the relationship between the molecular structure of the liquid-. crystalline polymers and the type of mesophase formed. The structure of smectic, nematic and cholesteric mesophases as well as models of chain packing in them are analyzed. The possibility to affect the strtcture of a liquid-crystalline polymer by an electric field is demonstrated.
Most of traditional chiral side-chain liquid crystalline polymers (SCLCP) depend on pendant chiral mesogenic units to introduce chirality in their structure, with the polymer backbones being usually achiral. In this work, we asymmetrically synthesize several enantiomerically pure norbornene monomers functionalized with achiral mesogenic units, and further apply ring-opening metathesis polymerization technique to prepare series of side-on and end-on SCLCPs with an optically active polynorbornene main chain and achiral mesogens. Their physical properties are fully characterized by NMR, UV, CD, GPC, TGA, DSC, polarimetry, polarized optical microscopy and small-angle X-ray scattering. The obtained side-on SCLCPs display the tendency of forming nematic, i.e. achiral mesophases, in strong contrast with the chiral nematic (cholesteric) mesophase exhibited by their comparative end-on analogues. The proposed explanation for this phenomenon is that the chiral backbones and the laterally attac...