SURFACE-TETHERED POLYMERS IN POLYMERIC MATRICES

Recently Budkowski et al. used nuclear reaction analysis to study polymer brushes consisting of end-tethered deuterated polystyrene tails within a polystyrene homopolymer matrix. They measured the concentration-depth profile as a function of the surface coverage sigma of tails and the degree of polymerisation of the matrix. For the matrix with the largest degree of polymerisation, the variation of the effective brush thickness L with sigma can be fitted by the apparent power law L is-proportional-to sigma(q) with q = 0.54 +/- 0.06. This scaling law is not expected theoretically for surface-tethered polymers exposed to a polymeric matrix consisting of chemically identical chains (chi = 0, where chi is the interaction parameter). In the present note we would like to propose an explanation based on the fact that mixtures of deuterated and protonated polystyrene chains are characterized by a small (but non-zero) value of chi.