Orientation of Phenyl Rings and Methylene Bisectors at the Free Surface of Atactic Polystyrene. Clancy, Thomas C.; Jang, Jee Hwan; Dhinojwala, Ali; Mattice, Wayne L. Institute of Polymer Science, The University of Akron, Akron, OH, USA. Journal of Physical Chemistry B (2001), 105(46), 11493-11497. CODEN: JPCBFK ISSN: 1089-5647. Journal written in English. CAN 136:70318 AN 2001:766903 CAPLUS

Atomistically detailed models of free-standing thin films and the bulk structure of amorphous atactic polystyrene were produced by reverse mapping from equilibrated coarse-grained models. The bridging technique employed in the simulation allows the generation of a moderate sized atomistic system (6 independent parent chains of C400H402, 4812 atoms) with a more reasonable computational effort than is required when all of the construction is performed on chains expressed with atomistic detail. Reverse mapping from the coarse-grained model to the atomistically detailed model is found to be straightforward, without ring piercing or concatenation. The calcd. surface energy (38 ± 10 erg/cm2) is in reasonable agreement with prior exptl. findings. The surface of the thin films is enriched in Ph rings. The rings at the surface tend to be oriented so that they are pointing outward, but rings in the middle of the thin film show no preferred orientation. In contrast with the Ph rings, the bisectors for the methylene groups show little tendency for orientation, even when the methylene groups are close to the surface. These observations in the simulation are in qual. agreement with conclusions reported recently (Gautam et al.,2000) and (Briggman et al., 2001), based on the application of new spectroscopic techniques to the characterization of polymer surfaces.