Nanoscale probing a glass transition temperature of heterogeneous azo-polymers using atomic force microscopy

Abstract

Azo-polymer materials found diverse applications in many interdisciplinary areas, including frequency conversion, surface relief grating and others. In such devices, stratified polymer systems are often used, in which each layer ranges from 5 nm to 100 nm in thickness. One of the key characteristics of the polymer is the glass transition temperature Tg, which indicates the thermal stability of polymer, depending on its thickness and environment. The method for determining Tg that used in this work is based on recording the dependence of the oscillation phase of an atomic-force microscope probe on the sample temperature. To study the possibility of determining the local Tg, a cross section of a multilayer polymer system, polyethylene/polyamide with the layer thicknesses of 50-100 nm, is used. Tg is measured by a change in the phase of oscillation of the cantilever, which is caused by the loss of energy of the cantilever due to the change in Gibbs energy of the polymer during the thermal expansion. It was possible to measure the local temperature within the glass transition points of the sample and for chemical identification methods used different areas of enhanced optical microscopy (nano - Raman and nano-IR).