Surface-Induced Chain Alignment of Semiflexible Polymers

Semiflexible polymers tend to spontaneously align parallel to an impenetrable surface, creating a mean aligning field. The backbone segments interact with the aligning field, further enhancing the chain alignment. Using molecular dynamics (MD) simulations of bead-spring chains, we demonstrate that the thickness of the aligned layer is about a persistence length L_p for semiflexible polymers in the isotropic phase. To investigate the effect of nematic coupling on the surface-induced alignment, we develop a lattice version of self-consistent field theory (SCFT) for semiflexible chains. We predict that the strength and range of the alignment increase with increasing nematic coupling, quantified by the nematic coupling constant α. The impenetrable surface acts as a perturbation on the chain alignment, and the nematic coupling α amplifies the perturbation. By comparing the SCFT predicted order parameter profile for chains near an impenetrable surface to MD simulations, we can estimate α for semiflexible polymers.