Statistical thermodynamics and configurational structure of chains confined between surfaces. Part 1.—Excluded-volume chains confined between a pair of non-adsorbing planes

Abstract

The problem of the excluded-volume chain confined between a pair of parallel plates has been tackled using a Monte Carlo simulation approach. The configuration generation technique devised previously for tetrahedral chains on a single surface has been suitably modified to take account of the second surface. The calculations are directed to the evaluation (a) configurational free-energy changes with variation in interplate separation, which in turn lead to the determination of the force of steric repulsion and (b) configurational properties relating to the mean dimensions of the chain and structure of the interfacial region. Both terminally anchored and non-anchored chains (with no segment/surface interactions) are considered. It is found that although the two systems possess similar forces of steric repulsion, only the terminally anchored chain gives rise to the stabilisation of the plates at all separations. In the presence of the non-anchored, excluded-volume chain, the plates are stabilised at large interplate distances but destabilised at small separations. Terminal anchoring causes the chain to expand and produces significant asymmetry in the system with the result that the values of the configurational quantities with respect to the two surfaces are unequal and the segment density distributions are skewed.