End group modification in poly(ethylene terephthalate)

The esterification reaction between the hydroxyl end groups in PET and trif luoroacetic acid on stirring at room temperature has been observed and stud ied. The reaction, which we refer to as end-capping, was found to be comple te after 5 days. We demonstrate that whilst the reaction leads to modificat ion of the end groups there is no significant degradation of the polymer ch ains. Proton nuclear magnetic resonance has been used to probe the kinetics of the reaction, and a pseudo first-order reaction rate constant of (7.8 /- 1.8) x 10(-6) s(-1) has been obtained. The results of this study may hav e implications for other polyester systems where strong acids are used as s olvents. (C) 1999 Elsevier Science Ltd. All rights reserved.