Polystyrene layers grafted to epoxy-modified silicon surfaces

Carboxylic acid- and anhydride-terminated polystyrenes of different molecular weights from 4500 to 672 000 were grafted from melt onto silicon substrates modified with epoxysilane monolayer. The grafted chains are densely packed with a density close to the known value for the bulk material. The tethered polymer layers are very smooth, uniform, mechanically stable, and cover homogeneously the modified silicon. At the degree of polymerization (N) close to the critical molecular weight, the grafting process is the most effective, resulting in the grafted unperturbed macromolecules. We suggest that the grafting from the reactive polymer melt is controlled by steric constraints through the minimum available free volume between the grafted macromolecules, which is reachable by another reactive end. This volume correlates with the size of monomeric unit and varies very Little with the molecular weight.