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

The weighted-density functional approach for polymer liquids near inte rfaces is generalized to freely jointed and stiff-chain molecules of a rbitrary length. The site-site approximation to the intermolecular int eraction potential is used for chains composed of tangent spheres, gra fted 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 monol ayer is discussed in relation to its dependence on the number of side branches of the star polymer and their stiffness. With increasing surf ace 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 flo ating branches. The other transition, from a monolayer with grafted br anches lying flat at the surface to a monolayer with upright orientati on of grafted branches, takes place when there is a strong attraction of grafted branches to the surface.