Roughening, deroughening, and nonuniversal scaling of the interface width in electrophoretic deposition of polymer chains

Growth and roughness of the interface of deposited polymer chains driven by a field onto an impenetrable adsorbing surface are studied by computer simulations in (2+1) dimensions. The evolution of the interface width W shows a crossover from short-time growth described by the exponent β₁ to a long-time growth with exponent β₂(>β₁). The saturated width increases, i.e., the interface roughens, with the molecular weight L_c, but the roughness exponent α (from W_s∼L^α) becomes negative in contrast to models for particle deposition; α depends on the chain length—a nonuniversal scaling with the substrate length L. Roughening and deroughening occur as the field E and the temperature T compete such that W_s≈(A+BT)E^-1/2.