Synthesis of a novel liquid crystalline copolyester with fractile structure

Poly ( ethylene terephthalate-co-p-oxybenzoate) (PET/HBA) is the first reported liquid crystalline polyester, and has higher strength than that of poly( ethylene terephthalate) (PET). However, there are two problems for the PET/HBA copolyester, chemical structure control and normal mechanical properties. Stepwise feed mode of p-oxybenzoate (HBA) can solve the first problem. The other should be solved by adding some flexible or non-linear monomers, but it will decrease the oriented mechanical properties. According to the fractile theoretic calculation, a fractile monomer, trihydroxy benzene (TOP), was introduced into the chain of PET/HBA copolyester to reduce the melting point and improve the processing properties of PET/HBA copolyester,and finally to increase the oriented and normal mechanical properties. The effects of copolycondensation time, acetylization time, pressure, TOP and HBA concentrations on the inherent viscosity of novel fractile copolyester were investigated. The effects of TOP and HBA concentrations on the melting point and isotropic temperature of novel fractile copolyester were also studied. A novel copolyester with fractile structure was obtained. With the increasing of TOP concentration, there were a maximum of the inherent viscosity and a minimum of the melting point for the novel copolyester. The melting point was lowered 10degreesC or more than that of PET/HBA copolyester. But the isotropic temperature and liquid crystalline texture of the copolyester was not changed with the increasing of TOP concentration. So, the range of liquid crystalline was enlarged.