Facile, Efficient Routes to Diverse Protected Thiols and to Their Deprotection and Addition to Create Functional Polymers by Thiol−Ene Coupling

Carbazole, dinitrobenzoate, phenol, pyridine, and 4-cyano-4‘-alkoxybiphenyl side groups were grafted onto pendant vinyl groups of polybutadiene (PB) by thiol−ene addition to yield functional polymer of polydispersity equal to that of the precursor material. Synthesis protocols that are clean (>90% conversion to desired product) and scalable were developed to incorporate a protected thiol group into functional precursors. The resulting acetyl or benzoyl thioesters are suitable for long-term storage, and are conveniently deprotected and added to polymer in a matter of hours in a straightforward procedure that does not require isolation of the thiol intermediate. Alternatively, PB functionalization could be achieved with equal success by reaction with β-mercaptoethanol (BME), and subsequent esterification of the incorporated hydroxyl groups with a suitable acyl halide. The chemistry described can potentially be applied to add any side group onto any polymer, copolymer, or block copolymer displaying pendant vinyl groups.