Transverse layering of molecular gyration spheres in spin-coated atactic polystyrene (aPS) films, for film thickness R≤ 4Rg (Rg = unperturbed gyration radius), causes an increase in free energy that does not follow the (Rg/R)−2 dependence of planar confinement and is explained by invoking a fixed-range, repulsive, modified P\"{o}schl-Teller intermolecular potential, its strength decreasing with increase in R. Vacuum ultraviolet spectroscopy reveals a change in 'physical dimers' of adjacent pendant benzene rings of aPS from 'oblique' to 'head-to-tail' configuration as film thickness goes from 9Rg to 2Rg. This reduces cohesion by reducing dimer dipole moment. Thus a new phase of aPS, the nanoconfined phase, ordered but with lower cohesion than bulk, is formed.
@article{arxiv.cond-mat/0610138,
title = {Nanoconfined Polystyrene: A New Phase},
author = {Sudeshna Chattopadhyay and Alokmay Datta and Avijit Das and Angelo Giglia and Stefano Nannarone and Nicola Mahne},
journal= {arXiv preprint arXiv:cond-mat/0610138},
year = {2007}
}