Substrate Effects on Glass Transition and Free Surface Viscoelasticity of Ultrathin Polymeric Films

It has been observed that glass transition temperature (Tg) of ultrathin polymeric films was different with bulk material. The reason for the changes in Tg for ultrathin films are still unclear, but one of commonly proposed idea is role of free surface and substrate effects. In the present study, we investigate the free surface and substrate effects on dynamic and viscoelastic properties of ultrathin polymeric films by employing nano particle embedment method on both single and multilayer films. By applying Hutcheson and McKenna’s viscoelastic contact mechanic approaches onto our experimental results, we are able to obtain rheological properties of the film surface.