Investigations at NIST on the influence of polymer-polymer excluded volume and polymer-surface interactions on the formation and swelling of end-grafted polymer layers are reviewed. Recent theoretical modeling of grafted layers having a low grafting density and variable surface and excluded volume interaction is summarized and the results are compared with the theory of grafted layers having a high grafting density brushes and with NIST measurements on model end-grafted polymer layers. The low grafting density theory and measurements both indicate that polymer-surface interactions can exert a substantial influence on the dimensions of grafted chain layers. The role of polymer-surface and excluded volume interactions on the growth of the polymer layer from a polymer solution is next considered. The modeling idealizes the chain grafting process as a random sequential adsorption of domains representing the polymer molecules where the degree of interpenetration is adjusted to model variable solvent quality. Both the theoretical modeling and experiments indicate that excluded volume interactions exert a strong influence on the final structure of the grafted chain layer. Finally, the swelling and elasticity of polymer brushes is compared to gels. It is suggested that it is reasonable to consider a grafted polymer layer to be a variety of gel where the crosslinks are constrained to lie on a surface.
Citation: Polymer Preprints
Pub Type: Journals
brush, gel, grafted polymer layers, random sequential adsorption, renormalization group