Phase transitions on adsorption of macromolecules

Abstract

The general theory of the conformational transition on adsorption of the individual macromolecule on a solid surface is developed. The statistical sum of the macromolecule on the surface is constructed by the method of generating functions. It is shown that change in the equilibrium state of the chain from the free to adsorbed on a rigid adsorbent comes about for a certain critical adsorption energy of the units, i.e. has the character of a phase transition (for N → ∞). An equation is constructed relating the critical adsorption energy to the characteristics of the chain and adsorbent. The order of the phase transition is analyzed and it is shown that it is determined by the distribution function of the lengths of the loops formed by the free chain relative to the virtual surface drawn through it, the geometric equivalent of the adsorbent. An expression is obtained for the order of the phase transition including the dimensionality of the free volume and adsorbent (the number of measurements according to which the extent of the adsorbent is infinite) and the exponent in the dependence of the size of the free chain on the degree of polymerization. The possibility of diverse phase transitions on adsorption of the macromolecules is shown.