Journal
MACROMOLECULES
Volume 49, Issue 2, Pages 547-553Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.macromol.5b02261
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Funding
- National Science Foundation under an AGEP GRS supplement [DMR-1004576]
- NSF [CHE-1310453]
- DOE Office of Science User Facility [DE-AC05-00OR22725]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1310453] Funding Source: National Science Foundation
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The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. The brushes were synthesized with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were more polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. The origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.
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