Localization and stretching of polymer chains at the junction of two surfaces

We present a molecular dynamics study on the stretching of a linear polymer chain that is adsorbed at the junction of two intersecting flat surfaces of varying alignments. We observe a transition from a two-dimensional to one-dimensional (1D) structure of the adsorbed polymer when the alignment, i.e., the angle between the two surfaces that form a groove,theta, is below 135 degrees. We show that the radius of gyration of the polymer chain R-g scales as R-g similar to N-3/4 with the degree of polymerization N for theta = 180 degrees (planer substrate), and the scaling changes to R-g similar to N-1.0 for theta < 135 degrees in good solvents. At the crossover point, theta = 135 degrees, the exponent becomes 1.15. The 1D stretching of the polymer chain is found to be 84% of its contour length for theta <= 90 degrees. The center of mass diffusion coefficient D decreases sharply with.. However, the diffusion coefficient scales with N as D similar to N-1, and is independent of theta. The relaxation time tau, for the diffusive motion, scales as tau similar to N-2.5 for theta = 180 degrees (planar substrate), which changes to tau similar to N-3.0 for theta <= 90 degrees. At the crossover point, the exponent is 3.4, which is slightly higher than the 1D value of 3.0. Further, a signature of reptation-like dynamics of the polymer chain is observed at the junction for theta = 90 degrees due to its strong 1D localization and stretching. (C) 2014 AIP Publishing LLC.