Longer time kinetics of collapse transition of polymer-surfactant complexes at interfaces near to collapse temperatures.

The later stages of the collapse transition kinetics of fractionated poly(N-isopropylacrylamide) (PNIPAM) chains at interfaces in the presence of the surfactant sodium dodecyl sulfate (SDS) were studied for molecular weights ranging from 4.5x10(5) to 1.6x10(6). The interfacial PNIPAM-SDS complexes were quickly heated to the temperatures that were near to the collapse transition temperatures. The longer time collapse of the PNIPAM-SDS complexes at interfaces was found to proceed through two stages. The collapse kinetics at the later stages was interpreted in terms of a "globule growth" model. It was found that under the experimental conditions, the fast relaxation time was independent of the molecular weight, whereas the slow relaxation time was weakly dependent on the molecular weight.