Phase transitions in adsorbed polymer systems

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Abstract
The conformational properties of an adsorbed polymer obtained elsewhere by means of statistical mechanics are discussed. The polymer is modelled by a string of beads (monomer units) connected by freely rotating bonds and is free to move in a three-dimensional continuum half-space. The conformation properties: the number and the mean square end-to-end distance of beads on the wall, the density of beads of the wall, and the centre-of-mass of the polymer, are tabulated as a function of the adsorption energy parameter W. Like lattice models, this continuum theory predicts a phase transition at a critical value of W=Wc However, unlike lattice models, it is amenable to quantitative analysis. Numerical results for W are presented for real polymer–solvent/substrate systems assuming that the adsorption energy of a monomer unit is due to dispersion interactions. It is found that physically accessible temperature induced adsorption/desorption phase transitions are possible. Also suggested is the theoretical possibility of these phase transitions being induced by varying the dielectric properties of the solvent, e.g. by appropriate admixture.

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