EFFECT OF FREE POLYMER ON THE STRUCTURE OF A POLYMER BRUSH AND INTERACTION BETWEEN 2 POLYMER BRUSHES

Self-consistent-field (SCF) calculations are presented of a planar gra fted polymer layer that interacts either with free polymer chains or w ith another grafted layer. Three different systems are studied. The fi rst is a grafted polymer layer immersed in a polymer solution. The int eraction between grafted and free polymer can significantly influence the grafted polymer volume fraction profile. For grafted chains that a re strongly stretched the lattice calculations are compared with the t heory of Zhulina, Borisov, and Brombacher (Macromolecules 1991, 24, 46 79). Good agreement is found when the free chain length is far smaller than the grafted chain length. The scaling behavior of the penetratio n of free polymer into the grafted layer is also studied for this syst em. In the second type of system the interaction between two grafted l ayers in the absence of free polymer is considered. The lattice calcul ations agree well with the theory of Zhulina et al. In the third syste m free polymer is present between the interacting grafted layers. If t his free polymer has a small chain length, its main effect on the inte raction free energy is the compression of the free grafted layers, and only repulsion is found. However, for larger chain lengths a depletio n attraction between the grafted layers appears.