Rapid synthesis and post-polymerization modification of poly(vinylene sulfide) via sequential nucleophilic thiol-yne/ene click reactions

Click chemistry has emerged as a versatile and robust polymerization technique for the construction of functional polymers. In this work, organocatalyst-mediated consecutive thiol-yne and thiol-ene click reactions were performed for the synthesis and modification of the electron-deficient poly(vinylene sulfide) (PVS) structure. PVS was prepared within an hour in the presence of 1,4-diazabicyclo[2.2.2] octane (DABCO) and in an anti-Markovnikov fashion, with a high molecular weight (M_n = 12.9 kDa) and high stereoregularity (88% E-isomer). Following various optimization studies using 1-propanethiol as the model thiol, the obtained PVS was modified with various thiols in chloroform for 10 min using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, resulting in thioacetal main chain polymers. The scope of thiols used in the modification studies spans from alkyl and cycloalkyl to aromatic and allylic, and the polymers were obtained with varying efficiencies. Primary alkyl and aromatic thiols exhibited high efficiencies ranging from 87% to 100%. Similar high efficiencies were found for secondary mercaptans (70% and 92%); however, a very low efficiency (5%) was found for a tertiary mercaptan due to steric hindrance. It is believed the proposed indirect polythioacetal synthesis method holds the potential to be utilized in bio-related applications and material science.