Seminars Archive

Onset of thermal degradation of ultrathin polyacrylamide films: An XPS, NEXAFS and XRR study

Abstract
There are several pathways through which a polymer can degrade such as
thermal, photo-induced, 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°C. The rate of degradation was found to saturate after
~3 hours 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°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.