COMMENSURATE AND INCOMMENSURATE CONFORMATIONS IN A SIMPLE-MODEL OF CRYSTALLINE HELICAL POLYMERS

We investigate a simple model of crystalline helical polymers which includes interchain interactions and the effects of non-zero temperatures. The object is to determine the conditions under which incommensurate phases are possible at high temperatures. We find a fundamental difference between lattices of two-fold symmetry and those of the higher symmetry typified by a hexagonal lattice. For helices of a preferred handedness, only two-fold symmetry prevents the formation of incommensurate structures. In higher symmetries incommensurate helices are almost always formed at sufficiently high temperatures.