SEGMENTAL DYNAMICS IN POLYSTYRENE ULTRATHIN FILMS STUDIED BY SINGLE MOLECULE FLUORESCENCE DE-FOCUS MICROSCOPY

摘要

@@Segmental dynamics of polymers under confinement is a very interesting topic in polymer physics(7, 2). The significance of the researches in this field also lies in the fact that it is related to the fundamental knowledge underlying numerous technologies and applications, such as coating, adhesion, microelectronic industry, nano-fabrication, etc. Polymer films with very small thickness comparable to the polymer chain dimension (for example, the radius of gyration, Rg) offers the ideal model systems for the investigation of confined polymers. According to previous studies(i), systems of this kind exhibit very unique glass transition behavior which is correlated with the segments dynamics directly compared with the bulk states. The most noticeable feature is the shift of glass transition temperature (T_g) compared with the bulk values. Studies show that this behavior may originate from a number of reasons: spatial confinement, free surface effect, polymer-substrate interactions, etc. Although various methods have been employed to explore the physical origins of the shift of T_g under polymers under confinement, unambiguous conclusion is yet not clear.