(316f) Impact Of Segmental Mobility On The Thermal And Mechanical Properties Of Thin Polymer Films

The thermal properties, especially T_g, of polymer thin films have been studied extensively for polystyrene, as functions of different physical properties ranging from surface energy of the support to molecular weight. Generally, T_g decreases with respect to the bulk value below a critical film thickness of approximately 30 nm. However, the presence of residual solvent can suppress or even eliminate the thickness dependence on Tg.¹ Minimizing required cooperative segmental motion has been suspected to be the root of this behavior,¹ and some modified styrenic-repeat unit structures tend to support this claim.²

Here we extend these studies to a homologous series of poly(alkyl methacrylates), whose bulk T_g and local segmental dynamics are directly related to the alkyl chain length. The impact of these small changes in the repeat structure on T_g, coefficient of thermal expansion (CTE), and Young's modulus is examined as a function of the film thickness.

References: 1. C.J. Ellison, R.L. Ruszkowski, N.J. Fredin, J.M. Torkelson. Physical Review Letters 2004, 92, 095702.

2. C.J. Ellison, M.K. Mundra, J.M. Torkelson. Macromolecules 2005, 38, 1767.