Molecular weight and chain architecture dependence of glassy compliance of ultrathin freely standing polymer films

Glassy compliance of ultrathin linear polystyrene films of different molecular weights was investigated with the novel nanobubble inflation techniques developed in our lab. Previous work by O'Connell, Hutcheson and McKenna [1] indicates that the glassy compliance decreases as the film thickness decreases for a polystyrene sample with molecular weight of 1M g/mol. However the glassy stiffening is not nearly as dramatic as that observed in the rubbery plateau regime [2]. Preliminary results in the present work show that the glassy compliance decreases as the molecular weight increases. We are now examining a three-arm star polystyrene with branch molecular weight the same as that of the lower molecular weight linear material and eight-arm stars will also be investigated with the purpose of determining chain architecture effects on the glassy and rubbery behaviors of ultrathin polymer films. \\[4pt] [1] P.A. O'Connell, S.A. Hutcheson and G.B. McKenna, J. Polym. Sci. Part B. Polym. Phys. Ed., \textbf{46}, 1952 (2008). \\[0pt] [2] P.A. O'Connell and G.B. McKenna, Eur. Phys. J. E, \textbf{20}, 143 (2006).