The effect of curing reaction on mesophase-rich islands of segmented main chain liquid crystalline oligoesters

A liquid crystalline oligoester (LCO), based on 4,4′-diacetoxybiphenyl and sebacic acid was prepared by melt-transesterification as a model. The LCO was cured in presence of a mixture of 75:25 of diglycidyl terephthalate and triglycidyl trimellitic acid ester (D&TGE), as a curing agent. In this paper, the effect of curing reaction on mesophase-rich islands of segmented main chain liquid crystalline oligoesters was investigated based on a model of hierarchical structure. We carried out depolarizing transmittance measurements, optical microscopy observations and Fourier transform infrared spectroscopy on the samples, which was cured at isothermal and non-isothermal conditions. The sample has been cured at its liquid crystalline state and the results showed that the mesophase-rich islands are locked in, even at room temperature. The size of domains was smaller in the cured state in comparison to the islands that were formed before the curing of LCO. The liquid crystalline oligoester, which was cured at its isotropic state, the sample remained at this order and no optical activity was observed in that. Further experiments revealed that the mesomorphic behavior of the sample before and after the curing reaction differs, and the curing process strongly influenced the liquid crystalline features of the sample.