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RESEARCH PRODUCT

Influence of molecular weight and polydispersity on phase behaviour of polyesters with laterally fixed or cross-shaped mesogens

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Abstract To supplement previous studies of polyesters with laterally attached and cross-shaped mesogens the influence of molecular weight and molecular weight distribution on the phase behaviour has been investigated. For that purpose two polyesters have been fractionated by preparative gel permeation chromatography under high pressure and observed by polarizing microscopy and DSC measurements. A monotropic nematic polyester with laterally attached mesogens shows changing phase transitions up to a molecular weight of 10 000 (Mw); at higher molecular weight only the clearing transition is still slightly influenced. The molecular weight distribution at an average molecular weight of 15 000 (Mw) has no influence on the melting and clearing temperatures, but does effect recrystallization. The tendency to recrystallize decreases with increasing polydispersity, with increasing aberration from a monomodal molecular weight distribution. The recrystallization and the melting enthalpy are most distinguished at mole...