Adsorption of Random Copolymer on a Chemically Heterogeneous Periodic Stripe-Patterned Surface

Abstract

The adsorption of a single random copolymer chain containing correlations in a sequence on the chemically heterogeneous periodic surface with the alternating striped texture is studied theoretically. The problem is solved within the framework of a partially directed walk polymer model in three dimensions using the generating functions approach and the annealed disorder approximation for averaging over the ensemble of random sequences of units in the copolymer. Dependences of the adsorption transition point on the composition of the random copolymer and the degree of correlation in the random sequence of units for various periodic surfaces are presented. It is shown that for compositionally symmetric and weakly symmetric surfaces there is the optimal composition of the random copolymer and the degree of correlation in the sequence of units, at which the inverse temperature corresponding to the adsorption transition point has a local minimum. In the case of the compositionally symmetric surface, the “optimal” random copolymer is also symmetric in composition. For surfaces with a pronounced composition asymmetry the best adsorbent is a homopolymer complementary to sites that prevail on the surface. The degree of asymmetry range, in which the dependence of the inverse transition temperature on the copolymer composition and the correlation parameter exhibits the local minimum, is fairly narrow.