Polymer‐dispersed liquid‐crystal polymers (PDLCPs). Morphology of the LCP droplets

Abstract

“Synthetic blends” of a flexible polymer forming the matrix and a liquid‐crystalline polymer (LCP) forming the dispersed phase have been prepared by transesterification of PET with a mixture of sebacic acid (S), 4,4′‐diacetoxybiphenyl (B) and 4‐acetoxybenzoic acid (H) in the mole ratio 1:1:2. A change of the synthesis conditions causes marked variations of the chemical composition and the morphology of the phases. The SEM investigation of the inner morphology of the LCP droplets of blends consisting of two phases with fairly different aromatic content has shown that the LCP macromolecules are aligned tangentially at the matrix surface boundary, and that the nematic director configuration is toroidal. When the two phases have closer chemical composition, and are therefore supposed to possess improved mutual compatibility, a perpendicular anchoring of the LCP fibrils to the matrix cavity surface, and an axial configuration of the nematic director, are observed. The expected effect of the nematic configuration of the LCP droplets on their ability to deform into fibrils under appropriate flow conditions is preliminarily discussed.

Effect of polymerization conditions on the microstructure of a liquid crystalline copolyester

“…The above considerations suggest that the results of previous studies,1–3 indicating that a blocky microstructure of the SBH copolyesters is obtained whenever the mole fraction of H in the monomer mixture exceeds about 50%, can only be explained on the basis of two equally important assumptions: (1) that as polymerization proceeds, the reaction mixture becomes biphasic and (2) that there is a thermodynamic tendency toward compositional differentiation of the two phases, rather than homogenization. This conclusion agrees with previous results found by some of us,14–16 showing that the transesterification of PET with the same mixture of monomers employed in this work fails to produce a random copolyester, as would be expected in a homogeneous reaction medium, and leads to distinctly biphasic materials just because the segregation of a fairly ordered liquid–crystalline phase provides an enthalpy gain that pushes the process in the ordering direction.…”