Phosphorus-containing thermotropic liquid crystalline copolyesters (BDQTE) with higher molecular weight and thermal stability

lower thermo-transition temperature and broader mesogenic temperature region

based on p-acetoxybenzoic acid (ABA)

terephthalic acid (TPA)

ethylene glycol (EG) and 2(6-oxido-6H-dibenz1

2oxaphosphorin-6-yl)-hydroquinone (DOPO-HQ)

have been synthesized via melting pre-polymerization along with solidstate polymerization (SSP).Thermal properties of the solid-state-polymerized BDQTE (SSP-BDQTE) were investigated via thermomechanical analyzer (TMA)

thermogravimetric analyzer (TGA)

differential scanning calorimeter (DSC) and polarized optical microscopy (POM).Through the investigations on intrinsic viscosity (［η］)

viscous flow temperature (Tf) and the carboxyl group-concentration (［COOH］) of the target copolyesters at different SSP stages

synthetic conditions and the control mechanism of SSP were also briefly discussed.Results suggested that increases of the SSP temperature and time had positive influences on the progression of polymerization

and an obvious diffusion-controlled mechanism existed in the SSP courses of BDQTE.When the SSP temperature reached 235℃

SSP-BDQTE with the optimal above-mentioned properties could be obtained.At the early stage of SSP carried out at 235℃

with the increase of reaction temperature and time

［η］

Tf and ［COOH］ of the SSPBDQTE changed sharply

but changed very slowly and even unchanged after about 6 h.