Characterization of Styrene-Vinyl Alcohol Copolymers by CP-MAS NMR Spectroscopy

The first solid-state characterization of statistical copolymers of vinyl alcohol and styrene (poly(VA-stat-St)) by cross-polarization magic angle spinning (CP-MAS) spectroscopy is described. Poly(VA-stat-St) is not available from the traditional feedstocks styrene (St) and vinyl acetate (VAc) due to a mismatch in reactivity ratios. BN 2-vinylnaphthalene (BN2VN) is a synthetic solution to this challenge as it copolymerizes with activated monomers (e.g., styrene, methyl methacrylate), and the BN naphthalene side chain can be oxidatively converted to hydroxyl (-OH) side chains. While high levels of BN2VN incorporation are readily achieved (e.g., > 75 mol % BN2VN), prior work has identified that poly(VA-stat-St) is poorly soluble in organic solvents when the molar fraction of VA exceeds 0.50, presumably due to the hydrophilic character of the hydroxyl group as well as possible interchain hydrogen bonding. Circumventing this solubility challenge, we describe quantitative solid-state C-13 CP-MAS spectra demonstrating high conversion (85-99%) of poly(BN2VN-stat-St) to poly(VA-stat-St). 11B CP-MAS confirmed the removal of organoborane functional groups.

Automated summary

This study presents the first solid-state characterization of statistical copolymers of vinyl alcohol and styrene using cross-polarization magic angle spinning (CP-MAS) spectroscopy. The research overcomes the compatibility issue of traditional feedstocks and achieves high conversion rates through a synthetic solution.