13C‐NMR spectroscopic analysis of vinyl groups in styrene–divinylbenzene networks

Publisher Website
Google Scholar
Abstract
p‐Divinylbenzene (DVB) 13C‐labeled at the methine carbon of the vinyl group was copolymerized in suspension with styrene at 70, 70–95, and 135–155°C using 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The number of unreacted vinyl groups in each copolymer was determined by 13C CP–MAS NMR analysis of solid samples, direct polarization 13C‐NMR analysis of CDCl3‐swollen gels, and bromination. Results from the three methods agree methods agree qualitatively. Even the 1% DVB‐crosslinked networks contained 40% unreacted DVB‐vinyl groups when prepared by high conversion polymerization at 70°C and 16% unreacted DVB‐vinyl groups when polymerization was finished at 95°C. The analyses were also applied to some commercial crosslinked polystyrenes. Every sample examined contained pendent vinyl groups