  The film thickness dependence of crystal growth is investigated for isotactic
polystyrene (it-PS) in thin films, the thickness of which is from 20nm down to
4nm. The single crystals of it-PS grown at 180 in the ultrathin films show the
morphology typical in the diffusion-controlled growth: dense branching
morphology (DBM), fractal seeweed (FS). The characteristic length of the
morphology, i.e. the width of the branch, increases with decreasing film
thickness. The thickness dependence of the growth rate of crystals shows a
crossover around the lamellar thickness of the crystal, 8 nm. The thickness
dependences of the growth rate and morphology are discussed in terms of the
diffusion of chain molecules in thin films.

Soft Condensed Matter