Semicrystalline Polymers via Ring-Opening Polymerization: Preparation and Polymerization of Alkylene Phthalate Cyclic Oligomers

Abstract

Preparation of cyclic oligomeric alkylene phthalates via pseudo-high dilution condensation of alkylene diols with iso- and terephthaloyl chlorides and conversion to high molecular weight polyesters via ring-opening polymerization is described. Sterically unhindered amines such as quinuclidine or 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyze the condensation significantly faster than other tertiary amines and are useful for carrying out this conversion in high yield, in the first direct reaction of diol and diacid chloride to form cyclic polyesters. The mixtures of oligomeric cyclics melt at 150−200° C, providing liquids of low viscosity. Ring-opening polymerization using tin or titanate catalysts affords high molecular weight polymers within minutes. Complete polymerization of PBT oligomeric cyclics can be achieved at 180−200 °C, significantly below the polymer's melting point of 225 °C, and with molecular weights as high as 445 × 10³. Polymers formed via such a process are more crystalline than conventionally prepared polyesters.