The molecular design of functional polymer surfaces

Date of Completion

January 2001


Engineering, Chemical




In many commercial applications of polymer systems it is important to be able to control the chemical constituents that reside at the surface. One of the more direct approaches to control surface functionality is through the use of functional homopolymers. The goal of this research is to understand the general behavior of functional polymer surfaces. A self-consistent mean field approach was used to calculate surface composition depth profiles for functional polymers of a variety of architectures. The results obtained from the model demonstrate how the location of the functional group along the chain, the number of adjacent functional groups and the surface energy difference between backbone and functional group units can be changed to design polymers that optimize either the location of low or high surface energy functional groups at polymer interphases. The optimum position for one low energy functional group is at the chain end. The degree of surface segregation of two low energy functional groups that are adjacent at one chain end is more than twice that for a chain with one low energy functional group at one chain end. The optimal structure for segregation of two high energy groups on a single chain is to position them together at the chain center. These theoretical results demonstrate that adjacency of functional groups is the most effective architectural variable for enhancing the degree of surface segregation in functional polymers. ^ To complement the theoretical study two different chain architectures were investigated experimentally: end and center fluorosilane functional polystyrene. Surface sensitive techniques confirmed that the end-functional architecture is the optimum one to create low energy surfaces. The surface structure and composition of blends of end-functional polymers and parent homopolymers and the restructuring phenomenon for surfaces of end functional homopolymers, in the glassy state was examined using the self consistent lattice model. The theoretical predictions were directly compared to experimental data. An active approach at controlling polymer surface properties was also investigated using azobenzene dye molecules. ^