Influence of chemical structure on glass transition temperatures of poly(propylene terephthalate) and poly(propylene isophthalate)

Poly(propylene terephthalate)

1 Systematic IUPAC name: poly(oxypropyleneoxyterephthaloyl).

(PPTP) and poly(propylene isophthalate)

2 Systematic IUPAC name: poly(oxypropyleneoxyisophthaloyl).

(PPIP) were prepared by melt polycondensation. Different fractions with number-average molar masses in the range 5 000 ? 20 000 g·mol^?1 were obtained and their respective glass transition temperatures (T_g) determined by calorimetry. The solubility parameters of the polymers were obtained by viscosity measurements in different solvents and were found to be 9,4 and 9,5 cal^1/2·cm^?3/2 (19,2·10³ and 19,4·10³ J^1/2·m^?3/2) for PPIP and PPTP, respectively. The glass transition temperatures were compared with those reported for analogous polyesters and it was shown that intramolecular interactions highly influence the T_g of these polyesters, whereas the effect of intermolecular interactions seems to be less important.