Thomas Hölzl, Markus Wittkop, Stefan Kreitmeier, Hans L. Trautenberg and Dietmar Göritz
We discuss structural aspects of three-dimensional polymer melts undergoing glass transition. Our Monte Carlo study is based on the well known bond-fluctuation model including van der Waals interaction and bond-length potential. Results are presented for different cooling rates and a wide range of temperatures. The glass-transition temperature, Tg, was determined by the significant change in various static and dynamic quantities, such as the static structure factor of individual polymer chains and the incoherent scattering function. Below Tg, the latter is characterized by division into a Debye-like short-time regime and two separate time regimes with stretched-exponential behaviour. Further investigation by means of block density distribution analysis revealed an inhomogeneous, non-Gaussian distribution of mass below Tg. A direct proof for the existence of cavities and clusters of effective monomers has been given by visualization via a two-dimensional projection technique.