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Catalyst-Free Click Polymerization of Thiol and Activated Internal Alkynes: A Facile Strategy toward Functional Poly(β-thioacrylate)s

Thiol–yne
click polymerizations have become efficient synthetic
tools for the construction of linear and hyperbranched polysulfides
with advanced functionalities. However, the polymerization reaction
of internal alkynes and thiols has been rarely utilized to prepare
functional polymers. In this work, a catalyst-free click polymerization
between activated internal alkyne and thiol was developed. The polymerizations
of 4,4′-thiodibenzenethiol (1) with dibutynoates
(2) and diphenyl­propiolates (3) were
performed in N,N-dimethyl­formamide
(DMF) at 60 °C, producing poly­(β-thioacrylate)­s (PTAs)
with high molecular weights (Mw up to
50300) and high stereoregularities (Z content up
to 84%) in high yields (up to 91%). The click polymerization can be
conducted smoothly in an open atmosphere without protection against
moisture and oxygen. The resultant PTAs possess good solubility in
common organic solvents and high optical transparency. Thanks to the
high contents of sulfur atoms, ester groups, and aromatic rings in
the polymers, their thin films show high refractive indices (n > 1.63) in the wavelength region of 400–1700
nm.
Moreover, the PTAs containing tetraphenylethene moieties exhibit aggregation-induced
emission characteristics.