Onset Kinetics of Thermal Degradation of Ultrathin Polyacrylamide Films

摘要

There are several pathways through which a polymer can degrade such as thermal, photoinduced, biological, chemical and mechanical. The thermal degradation process of polymers is widely studied because of both academic and industrial interest. Here we have investigated the kinetics of thermal degradation and structural modification of polyacrylamide ultrathin films as a result of heat treatment at the degradation onset temperature. The chemical analysis of the material was performed using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption Fine structure (NEXAFS) spectroscopy. The formation of imide functionalities was found to occur on the polymer chains with simultaneous breakdown of amide groups, The kinetics of the degradation products obtained from quantitative analysis of the XPS spectra shows that the thermal degradation of the major part of the polymer occurs within the First 30 min of heating at the onset temperature of 220 degrees C. The rate of degradation was found to saturate after similar to 3 h of heating. The structural aspects of the heated films were studied using X-ray reflectivity (XRR). Analysis of the reflectivity data shows that the thickness of the film decreases and the electron density increases after prolonged heating at 220 degrees C. From the amplitude of the reflectivity data, it was found that the interfacial morphology of the film stays almost unmodified and the film retains the polymeric property even after undergoing thermal degradation. The final onset degradation product obtained was ultrathin films of polymer containing 60% and 40% mono- and bicyclic imide functionalities, respectively.