화학공학소재연구정보센터
Macromolecules, Vol.27, No.6, 1617-1626, 1994
Structure of Adsorbed Polymer Layers - Molecular Volume Effects
A new continuum model for homopolymer adsorption is developed within the framework of self-consistent field theory. The model differs from previous lattice-based and continuum models in that it properly accounts for polymer stiffness in the idealization of a polymer molecule as a chain of segments and it allows segments and solvent molecules to have differing partial molar volumes. The altered balance of mixing enthalpy and entropy has quantitative implications for the structure of adsorbed polymer layers. Beginning with a heuristic development of a free energy balance for the system, functional minimization of the free energy determines the appropriate form of the self-consistent field. The field appears in a modified diffusion equation which governs the spatial distribution of polymer. This equation is solved via a regular perturbation expansion in powers of reciprocal polymer molecular weight. Retention of only the first term precludes tails but allows a semianalytical solution. We explore the effects of varying polymer-solvent interactions and partial molar volumes upon adsorbed layer structure, and we compare predicted polymer adsorbed masses and layer thicknesses with experimental values.