Glass transition of thermotropic polymers based upon vanillic acid, p-hydroxybenzoic acid, and poly(ethylene terephthalate)

✍ Scribed by Xin-Gui Li; Mei-Rong Huang; Gui-He Guan; Tong Sun

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 615 KB
• Volume: 59
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19960103)59:1<1::aid-app1>3.0.co;2-y

✦ Synopsis

SYNOPSIS

Differential scanning calorimetry (DSC) and dynamic mechanical and thermomechanical analyses are used to study the glass transition temperature (T,) of the thermotropic liquid crystalline polyesters prepared by molten polycondensation of 4-acetoxyvanillic acid (V), 4-acetoxybenzoic acid (B), and poly(ethy1ene terephthalate) (E). The polyesters exhibit two glass transition ranges at 66-83 as well as 136-140°C, which are attributed to E segmental motion in the E-rich/B-rich phases of the polyesters, as well as to the local mobility of the B component in the B-rich phase. The lower T, of the polyesters increases with an increase in the B and V unit contents or with increasing heating rate in the DSC measurements, but the higher T, decreases slightly. The experimental Tc values are compared with the T, values predicted from three equations on the basis of the sequence distribution and the monomer reactivity ratio of the polyesters. Uematsu's, Johnston's, and Couchman's equations all give a better fit with the experimental results.