NEW THERMOTROPIC COPOLY(KETO ESTERS) BASED ON 3,4'-DISUBSTITUTED BENZOPHENONES

Two isomeric benzophenone derivatives, 3-hydroxy-4'-carboxy- and 4-hyd roxy-3'-carboxybenzophenone, were synthesized and used to prepare new home-and copoly(keto esters) with some commercial comonomers. Polymeri zations were performed both by solution and melt polycondensation meth ods which affect the inherent viscosity and solubility of the resultan t products. Yields were always almost quantitative independently of th e synthetic method employed. All the samples exhibited very high therm al stability. Phase behaviour and morphology of the polyesters have be en investigated by differential scanning calorimetry (DSC) analysis an d optical microscopy. A liquid-crystalline (LC) phase was observed in most of the specimens containing commercial hydroxy acids in percentag es higher than 30 mol-%, while both homopolymers melt to an isotropic liquid. Preliminary gravimetric sorption experiments, using acetone as a penetrant, were carried out on films prepared from some of the copo lymers able to give both isotropic non-crystalline and nematic LC morp hologies. The penetrant sorption was strongly reduced by the presence of the frozen nematic LC phase that behaves similarly to the conventio nal crystalline ordered state.