X-ray Reflectivity Evaluation of the Thermal Cycling Effects in Methylcellulose Thin Films

Abstract

Changes in the layer thickness and roughness of as-prepared methylcellulose (MC) films with thermal cycling were studied using the X-ray reflectivity technique. It was found that thermal stress induced by rapid and slow thermal cycling brings no apparent changes in the surface and interface roughness after thermal cycling. On the other hand, some reduction of layer thickness was observed. With rapid thermal cycling, the relative shrinkage of the films is much higher at a maximum of 5% change at 15 cycles. With slow thermal cycling, it remains at a maximum of 3.6% even after 20 thermal cycles. Such film shrinkage is highly dependent on the initial film thickness and the amount of absorbed water molecules in the film.