Effect of flexibility of polymer chains on the kinetics of adsorption of polymer mixtures from solutions

The study of the kinetics of adsorption of polymers from solutions of mixtures of polymers with different thermodynamic flexibility (sigma) of polymer chains, such as cellulose triacetate (CTA) (sigma = 6.0) and poly (butylmethacrylate) (PBMA) (sigma = 2.0) has been done. Aerosil was used as an adsorbent. Adsorption parameters, such as an adsorption value (Gamma), adsorption interaction energy (Q) and degree of the adsorbent surface coverage (theta) were determined by infrared spectroscopy. The adsorption rate (V = partial derivative Gamma/partial derivative t) at different parts of the kinetic characteristics, and diffusion coefficients (D) in the adsorption process also were calculated. The values of the diffusion coefficients (D = 5.0 x 10(-12) to 7.0 x 10(-14)) determined for binary and ternary polymer solutions indicate high restraint of polymer macromolecules in the solutions. In such conditions, the adsorption rate is limited by the integration of the new adsorbing macromolecules to the already formed adsorption layer for establishing the equilibrium conformation. The data on the adsorption interaction energy and the degree of the adsorbent surface coverage for both polymers by adsorption from binary and ternary solutions are discussed. The obtained results provide a possibility to determine the relationship between the kinetic and thermodynamic parameters that affect the structure of the adsorption layer in the process of establishing the adsorption equilibrium. (C) 2007 Elsevier B.V. All rights reserved.