Electrophoretic deposition of polymer chains: a Monte Carlo study of density profile and conformation

Effects of molecular weight (L-c) and field strength (E) on conformation of polymer chains and their density are investigated at the surface and bulk of a driven chain system in three dimensions with a Monte Carlo simulation. As the polymer chains deposit on the surface, a linear density gradient de velops in low field. While the gradient becomes steeper on increasing the f ield in low L-c, onset of oscillation in the polymer density profile appear s with higher L-c, above a characteristic value of field (E-c) which decrea ses with increasing molecular weight. The substrate coverage (theta (j)) ex hibits a rapid increase on increasing the Field and tends to decline at hig h fields. In the bulk, the polymer density decreases rapidly with the molec ular weight while the substrate coverage (theta (j)) decays exponentially, theta (j) similar to e(-beta Lc). The radius of gyration (R-g) of chains un dergoes a crossover from SAW to rodlike conformation in the bulk on increas ing the field. On the surface, chains are longitudinally compressed with a sub-SAW conformation, i.e., the scaling exponent v similar to 0.50 - 0.55(R -g similar to L-c(-v)). Nonmonotonic response with opposite trend is observ ed in the variation of the longitudinal (minimum) and transverse (maximum) components of the radius of gyration with the field.