INFLUENCE OF SURFACE INTERACTION AND CHAIN STIFFNESS ON POLYMER-INDUCED ENTROPIC FORCES AND THE DIMENSIONS OF CONFINED POLYMERS

The theories of Dolan and Edwards [Proc. R. Soc. London Ser. A 337, 50 9 (1974)] and Eisenriegler et al. [J. Chem. Phys. 77, 6296 (1982)] for Gaussian chains confined between parallel plates and to a half-space are generalized to chains having arbitrary stiffness. The generalized theory exploits a recently discovered relation between semiflexible po lymers and Euclidean-type Dirac fermions in which ''flexible'' and ''s tiff'' polymers correspond to the nonrelativistic (massive) and relati vistic (massless) limits of the Dirac propagator, respectively. We sho w that half-space and parallel-plate problems are interrelated and thi s allows for a simplified and unified treatment of confined semiflexib le polymers. The properties of confined semiflexible chains exhibit a complicated dependence on the polymer-surface interaction and chain st iffness. Results for polymer dimensions and entropic Casimir-like forc es between plates are consistent with those obtained previously for fl exible chains and corresponding results are obtained for semiflexible polymers. The new results for the forces between plates, having a semi flexible polymer in the gap, exhibit qualitative agreement with experi mental data on confined chains at nonvanishing concentrations.