A series of vinyl sulfonate and vinyl sulfonamide monomers as Michael acceptors were synthesized and utilized to explore its features by systematic study of the monomer reactivity towards thiol in Photo-base catalyzed thiol-Michael reactions. Furthermore, the multifunctional derivatives were implemented in designing crosslinked polymeric material for improved mechanical properties. Previously, our group has reported the thiol-vinyl sulfone networks containing high weight fractions of sulfone groups which exhibited an improved T<sub>g</sub> at ambient temperature. The efficiency and versatility displayed by click Michael type additions to vinyl sulfone prompted us towards vinyl sulfonate and vinyl sulfonamide group.<br/>On investigating the scope of the designed Michael-acceptors with a systematic kinetic study, it demonstrated that the vinyl sulfonate reactivity is significantly higher than acrylate while acrylate exhibited slightly higher reactivity when compared to vinyl sulfonamide. The relative rates of the Michael addition to unsaturated sulfonate, sulfone, ester, and amides could be related to the electrophilicity of the enoyl carbon. The lower reactivity of vinyl sulfonamide as compared to vinyl sulfonate could be attributed to the lower electronegativity of the nitrogen instead of oxygen.<br/>The designed multifunctional derivatives where transformed to form uniform network polymers with the neat stoichiometric mixtures (per functional group concentration) of commercial thiol PETMP and ester free thiol SiTSH. As it is a neat thiol-Michael network polymer, it possess the attributes of step-growth reaction which includes high functional group conversion as well as uniform network structure. Our investigation demonstrated that the thiol-vinyl sulfonamide cross-linked polymers exhibited high glass transition temperatures, along with improved hydrolytical stability, thermal stability and mechanically strengthened material.

Development of vinyl sulfonate and vinyl sulfonamide: Its implementation in thiol-michael crosslinking polymerization

255th National Meeting (2018)

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