Abstract
4, 4′-Dihydroxy-3, 3′, 5, 5′-tetramethoxybiphenyl HMB) was prepared from 2, 6-dimethoxyphenol. Polyesterification of HMB with terephthaloyl, isophthaloyl and sebacoyl chloride were carried out by the low temperature solution polycondensation and the interfacial polycondensation. The polyterephthalate having inherent viscosity (ηinh) of 1.42 was obtained by the interfacial poly-condensation. The low temperature solution polycondensation using chloroform as a solvent gave the polyisophthalate having ηinh, of 0.73 and the polysebacate, ηinh of 0.43.
Thermal properties of the polyesters obtained were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The starting temperature of decomposition (Td) of each polymer was determined by TG. Td′s of the polyterephthalate, polyisophthalate and polysebacate were 341, 345 and 315°C respectively. The difference of thermal stability between the polyesters with methoxyl groups in biphenyl units and those without methoxyl groups was not prominent.
X-ray diffraction diagram of the polyterephthalate showed a crystalline pattern. However, no thermal transition such as melting were observed in the DSC of this polymer. X-ray diffraction diagrams of the polyisophthalate and polysebacate did not show any crystalline pattern. Glass transition temperatures of these polymers were observed at 252 and 94°C, respectively, in DSC measurements.
