NONEQUILIBRIUM CHARACTERISTICS OF A 2-DIMENSIONAL ULTRATHIN-FILM PREPARED BY THE WATER CASTING METHOD

A two-dimensional ultrathin film was defined as being a film thinner t han the dimension of an unperturbed Gaussian chain in the three-dimens ional state. The segment density of an unperturbed chain in equilibriu m in the two-dimensional solid state was investigated using a Monte-Ca rlo simulation. When the film thickness exceeds 30% of twice the radiu s of gyration of a three-dimensional unperturbed chain, the segment de nsity is not particularly high in comparison with the three-dimensiona l state. This means that a polymer chain will behave as a two-dimensio nal unperturbed chain in the equilibrium state of a two-dimensional ul trathin film, as in a three-dimensional solid state. Therefore, the ex cess expansion of a polymer chain in a two-dimensional ultrathin polys tyrene film with a thickness comparable to twice the radius of gyratio n of a three-dimensional unperturbed chain might arise from non-equili brium characteristics. In addition, the relaxation behaviour of a two- dimensional ultrathin film of a styrene-butadiene-styrene (SBS) triblo ck copolymer was investigated by transmission electron microscopy. The two-dimensional ultrathin SBS film contracted and decomposed into two phases (polystyrene and polybutadiene) from the one phase right after the film preparation. This indicates that the two-dimensional ultrath in film was in a distinct non-equilibrium state right after spreading a solution on the water surface.