Evidence that three-regime kinetics is inherent to formation of a polymer brush by a grafting-to approach

Abstract

Results are presented supporting the hypothesis that a three-regime kinetics profile, regardless of chemical structure of the polymer chains, molecular weight, type, of solvent and identity of the grafting surface, is inherent to polymer brushes formed by the grafting-to approach. However, the manifestation of the three-regime kinetics profile depends on grafting conditions, e.g., grafting temperature and concentration of free polymer in solution. Too high a temperature or solution concentration can lead to compression of the three distinct regimes on the time axis into what appears to be single-step brush formation, whereas low enough temperature and concentration leads to manifestation of all three regimes of kinetics. Also found was that, even when three regimes of kinetics were in evidence, grafting to a gold surface is much faster than grafting to a derivatized silica surface. Finally, the kinetics of the transition from mushroom to brush, denoted as the third regime, was found by fitting to a classical mathematical model of autocatalysis to be consistent with an autocatalytic process.