No abstract

In this paper the glass transition temperature (T g) in thin polymer films has been studied. Ellipsometry has been used to measure T g of poly(α-methylstyrene) (PAMS) thin films as a function of the film thickness for two molecular weights. When the films were thinner than a few hundred angstroms, substantial reduction in T g was apparent. The T g depression pattern did not show the difference between molecular weights. The Michaelis−Menten equation was adapted and used to fit the experimentally obtained T g data. From this analogized Michaelis−Menten function fitting, the fitting parameters T g, ∞ and ξ could be obtained. The obtained T g, ∞ corresponded with the bulk T g, and the parameter ξ was correlated with the statistical segment length. A continuous multilayer model was proposed and derived to describe the effect of surface on the observed T g reduction in thin films, and the depth-dependent T g profile was obtained. These results showed that T g at the top surface was much lower than the bulk T g and gradually approached the bulk T g with increasing distance from the edge of the film. The model and equation were modified to apply for the polymer coated on the strongly favorable substrate and the freely standing film.

We demonstrated a self-assembly of two different kinds of nanoparticles simultaneously directed on a monolayer film of diblock copolymer micelles via physical and chemical arrangements. We first incorporated gold nanoparticles physically around the micelles of a monolayer film of PS-PVP micelles having a short-range hexagonal order. Iron oxide nanoparticles were then synthesized chemically in the PVP core area of the ordered micelles, resulting in a mosaic nanopattern of magnetic iron oxide nanoparticles surrounded by metallic gold nanoparticles. Thus, we were able to direct two kinds of nanoparticles to self-assemble in the specific positions as an example of controlled fabrication of nanometer-sized building blocks.