Influence of Isosorbide on Glass-Transition Temperature and Crystallinity of Poly(butylene terephthalate).

Copolyesters of isosorbide and 1,4-butane diol were prepared by Ti(OBu)4-catalyzed transesterifications with dimethyl terephthalate in bulk at temperatures up to 250°C. The content of isosorbide was considerably lower than expected from the feed ratio and the molar masses were low, so that no DSC measurements were conducted. Copolycondensations of isosorbide and 1,4-butane diol with terephthaloyl chloride were either performed in dichloromethane at 40°C or in toluene at 100°C. The second method gave the higher molar masses. However, both series of polycondensations had the content of isosorbide roughly paralleled the feed ratios in common. The DSC measurements revealed that even 6 mol% of isosorbide is sufficient to raise the glass-transition temperature (Tg) by 10-12°C (up to 55°C). With 50 mol% of isosorbide, the Tg reaches 100°C. Yet, incorporation of isosorbide also reduces the melting temperature Tm and the degree of crystallinity, and a mol percentage above 30% prevents crystallization completely. In summary, incorporation of isosorbide allows for fine-tuning of Tg and Tm of poly(butylene terephthalate) over a wide range. [ABSTRACT FROM AUTHOR]