Depleting Depletion: Maintaining Single-Walled Carbon Nanotube Dispersions after Graft-to Polymer Functionalization

Adam Clancy, Hannah Leese, Noelia Rubio, David Buckley, Jake Greenfield, Milo Shaffer

Research output: Contribution to journalArticle

5 Citations (Scopus)
16 Downloads (Pure)

Abstract

Grafting polymers onto single-walled carbon nanotubes (SWCNTs) usefully alters properties but does not typically yield stable, solvated species directly. Despite the expectation of steric stabilization, a damaging (re)dispersion step is usually necessary. Here, poly(vinyl acetate)s (PVAc's) of varying molecular weights are grafted to individualized, reduced SWCNTs at different concentrations to examine the extent of reaction and degree of solvation. The use of higher polymer concentrations leads to an increase in grafting ratio (weight fraction of grafted polymer relative to the SWCNT framework), approaching the limit of random sequentially adsorbed Flory "mushrooms" on the surface. However, at higher polymer concentrations, a larger percentage of SWCNTs precipitate during the reaction; an effect which is more significant for larger weight polymers. The precipitation is attributed to depletion interactions generated by ungrafted homopolymer overcoming Coulombic repulsion of adjacent like-charged SWCNTs; a simple model is proposed. Larger polymers and greater degrees of functionalization favor stable solvation, but larger and more concentrated homopolymers increase depletion aggregation. By using low concentrations (25 μM) of larger molecular weight PVAc (10 kDa), up to 65% of grafted SWCNTs were retained in solution (at 65 μg mL-1) directly after the reaction.
Original languageEnglish
Pages (from-to)15396-15402
Number of pages7
JournalLangmuir
Volume34
Issue number50
DOIs
Publication statusPublished - 18 Dec 2018

ASJC Scopus subject areas

  • Materials Science(all)

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