To obtain lower chain length dispersity in surface-initiated (SI) polymer brushes, brushes were grown by ATRP in the presence of an end-capping group. Growing the SI brushes on high surface area nylon filters provided sufficient polymer for characterization after surface cleavage. SI grafting-from brushes are reported to exhibit a concentration gradient with the monomer concentration increasing with increasing distance from the surface. This gradient has been proposed to increase the growth rate of longer chains at the expense of shorter ones, as the active polymer ends move further from the surface. Limiting the DP of the polymer chains by the addition of a monomer that is known to propagate very slowly, such as a-methyl styrene (aMS), might be expected to limit the growth of fast-growing chains, giving the shorter chains a chance to catch up. As a comparison, we synthesized solution-grown polymers with the same monomer to aMS ratios. GPC and NMR analysis of the cleaved brushes showed a decrease in dispersity in both systems, but with the DP tending to higher in the SI system. The proposed mechanism and prospect of the approach to SI brush growth will be presented.

Effect on dispersity of end-capping in ATRP-grown surface-initiated brushes

2019 Spring National Meeting

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