CONFORMATIONAL PROPERTIES OF LINEAR AND STAR POLYMERS GRAFTED TO A SOLID-SURFACE

The weighted-density functional approach for polymer liquids near interfaces is generalized to freely jointed and stiff-chain molecules of arbitrary length. The site-site approximation to the intermolecular interaction potential is used for chains composed of tangent spheres, grafted to the planar solid surface. The gradual collapse of a monolayer of grafted linear chains and star polymers with decreasing temperature is described. The specificity of conformations in the collapsed monolayer is discussed in relation to its dependence on the number of side branches of the star polymer and their stiffness. With increasing surface coverage, two first-order phase transitions are also described in the films of stars with stiff chains. One of them is an order-disorder transition in the dense layers parallel to the surface, packed by floating branches. The other transition, from a monolayer with grafted branches lying flat at the surface to a monolayer with upright orientation of grafted branches, takes place when there is a strong attraction of grafted branches to the surface.