The effect of molecular weight on the dynamics of adsorbed poly(N-isopropylacrylamide) at particle surfaces in water

The relaxation dynamics of poly(N-isopropylacrylamide) (PNIPAM) at surfaces of poly(N-tert-butylacrylamide) latex particles was studied to determine t he influence of molecular weight on the relaxation process of interfacial P NIPAM chains. The relaxation dynamics of adsorbed PNIPAM layers under the p resent experimental conditions was postulated to include the extended-to-lo opily adsorbed state transition of tightly adsorbed chains and the diffusio n of tenuously adsorbed or dangling chains, combined with a slow conformati onal equilibrium. The dynamics was described by a nonexponential rate proce ss. The relaxation times calculated were found to show a weak dependence on molecular weight. The kinetic constraints for the relaxation in the presen t system are believed to be stronger than those in the normal polymer adsor ption from solutions.