Towards a theory of the coil-globule transition in comb-like macromolecules

The existing theory of the coil-globule transition in linear chains is extended in the present paper to the class of comb-like macromolecules. If the degree of polymerization is sufficiently great, the globule formed has a spherically symmetrical structure with a large spatially uniform core; in the surface layer, the density of side-chain ends decreases rather more slowly than does the density of main-chain links; the coil-globule transition occurs in the same way as in a linear chain. If the degree of polymerization is not very large, and only the ends of the side chains interact (have poor solubility), the interacting links form a drop-like nucleus of the globule and the continuous chain surrounds this nucleus; in order to describe the system, it is necessary to know only the equilibrium concentration of a saturated solution of the separated links, not any other characteristics of the volume interactions; the coil-globule transition occurs as a first order phase change; on going from a linear chain to a star-shaped chain, the transition temperature falls monotonically in the case of a flexible main chain but passes through a maximum in the case of a rigid main chain.