Layering and relaxation in molecular films of a photosensitive polyacrylate from X-ray reflectivity and in elastic neutron scattering experiments

Abstract

In this paper we study the eOE ect of ultraviolet (UV) illumination on the microscopic structure of molecular layers of a photosensitive fragile polymeric glass former. In particular we show that the increased time relaxation and the reduced mobility of thin molecular multilayers recently reported using highprecision pump±probe ellipsometric experiments correlate with a geometrically induced layering eOE ect which was con®rmed by synchrotron X-ray re¯ectivity experiments. Furthermore the results agree also with recent inelastic± quasielastic neutron scattering measurements of the coupling between the photosensitive side chains and the polymeric main chain. The observed layering is destroyed upon UV illumination. The signi®cance of such results on the glass transition behaviour of this material is discussed.