Polymer Degradation and Stability 30 (1990) 181-193 Surface Electrochemical Reactions and the Subsequent Degradation of Solid-phase Poly(ethylene terephthalate) at a Cathode A. A. Pud Institute of BioorganicChemistry,Academyof Sciencesof the Ukrainian SSR, Murmanskaya Str. 5, 252660, Kiev-94, USSR (Received 23 September 1989; accepted 23 November 1989) ABSTRACT Electrochemical and spectral methods have been usedfor the investigation of surface electrochemical reactions and reducing degradation (ECRD) of polyethylene terephthalate (PETP) in the presence of O.05 M of N(C4H9) J. This type of degradation occurs due to the electrochemical reduction of the terephthalate groups of PETP macromolecules in the region of the three- phase polymer-electrode-solution interface during cathodic polarization of the electrode. The electrochemical behaviour of PETP and its degradation products have been studied. This has allowed us to propose a mechanism of PETP ECRD which includes two-electron reduction of the terephthalate groups, decay of charged macromoleeules, transition of charged fragments into the solution volume and their protonation. Analysis of the dependence of the degree of PETP ECRD (~) on the quantity of electricity (Q) which passed through the system, permitted us to suggest the equation ct = 1 - exp ( - kQ) to describe satisfactorily the initial stage of polymer ECRD. INTRODUCTION The characteristics of electrochemical electron transfer reactions with the functional groups of polymer in solution are determined to a great extent by the donor-acceptor properties of these groups, by their interaction, by the conformation of the macromolecules, by the diffusion rate of the latter in the neighbourhood of the electrode, 1 by their orientation and mobility in the field of the electric double layer (EDL) of the electrode and by the 181 Polymer Degradation and Stability 0141-3910/90/$03"50 © 1990ElsevierSciencePublishers Ltd, England. Printed in Great Britain