Simulated glass transistion in free-standing thin polystyrene films

In this article, we investigate the glass transition in polystyrene melts and free-standing ultra-thin films by means of large-scale computer simulations. The transition temperatures are obtained from static (density) and dynamic (diffusion and orientational relaxation) measurements. As it turns out, the glass transition temperature of a 3 nm thin film is 60 °K lower than that of the bulk. Local orientational mobility of the phenyl bonds is studied with the help of Legendre polynomials of the second-order P2(t). The and relaxation times are obtained from the spectral density of P2(t). Our simulations reveal that interfaces affect and -relaxation processes differently. The relaxation rate is faster in the center of the film than near a free surface; for the relaxation rate, an opposite trend is observed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1160-1167, 201