Single-step solution polymerization of poly(alkylene terephthalate)s: synthesis parameters and polymer characterization

Poly(alkylene terephthalate)s represent one of the most frequently used polymer classes worldwide. Well-known examples include poly(ethylene terephthalate) (n = 2) and poly(butylene terephthalate) (n = 4). The conventional synthesis method for these polymers is based on melt polycondensation, a two-stage process performed under harsh conditions that includes the synthesis of an intermediate prepolymer and the presence of a catalyst, which may induce toxicity issues. The present work reports on a straightforward single-step solution polycondensation method performed under mild conditions and in the absence of a catalyst. A homologous series of poly(alkylene terephthalate)s (n = 5 − 10) of molar masses up to 20 000 g mol −1 and dispersity <2.4 was synthesized and characterized thoroughly. Great attention was given to the thermal properties assessment by using state-of-the-art techniques and a highly sensitive prototype technique called rapid heat − cool DSC. Similar to melt-synthesized polyesters, a particular odd − even trend of the thermal properties versus the number of methylene groups within the monomer unit was revealed. To the best of our knowledge, this is the first report covering a single-step solution-based polycondensation performed in the absence of a catalyst that results in highly reproducible polyesters possessing unaltered thermal properties compared to polyesters synthesized through industrially applied conventional routes.