ESTER INTERCHANGE REACTIONS IN POLY(ETHYLENE-TEREPHTHALATE) - OBSERVATION USING SMALL-ANGLE NEUTRON-SCATTERING

Ester interchange reactions have been studied in poly(ethylene terephthalate) (PET) by means of small-angle neutron scattering (SANS). Cast film PET samples containing 20 wt% deuterated PET chains were prepared at low temperature. The SANS molecular weight of the as-prepared specimens agrees with the g. p. c. value and the molecular dimensions are close to the unperturbed value. Samples were then annealed at temperatures of 150 degree C-300 degree C at times from 10-600 min. If ester interchange occurs in a blend sample, block copolymer chains are formed with the blocks consisting of protonated and deuterated sequences. The SANS M//w obtained from these samples is an apparent M//w, the M//w of the blocks, and is lower than the g. p. c. value. Ester interchange is shown to be rapid in the melt and also to take place at a slower rate at temperatures 15 degree C below T//m, in general agreement with previous studies. An apparent clustering effect at elevated temperatures is also reported.