New route to poly(alkylene terephthalate)s by reaction of dimethyl terephthalate with cyclic carbonates

A new route to poly(alkylene terephthalate)s by melt reaction of dimethyl terephtalate (DMT) with cyclic aliphatic carbonates such as ethylene carbonate and propylene carbonate is described. Poly(butylene carbonate) was used instead of the cyclic monomer for the synthesis of poly(butylene terepthalate). The polymers prepared by this alternative way presented a reduced amount of carboxyl end groups. These end groups are responsible for the poor thermal and hydrolytic stability of poly(alkylene terephthalate)s industrially prepared from DMT or phthalic acids and the corresponding diols. The thermal studies conducted on poly(propylene terephthalate) samples, obtained by this innovative procedure, confirmed the expected higher thermal stability. A detailed study of the mechanism, using a model compound, of this new route for polyesters synthesis together with a complete characterisation of the polymers prepared, is described.