Economic Sulfur Conversion to Functional Polythioamides through Catalyst-Free Multicomponent Polymerizations of Sulfur, Acids, and Amines

Sulfur utilization is a global concern
because of its abundant
nature sources and the safety or environmental problems caused by
its burning or oxidation during storage, while sulfur-containing polymers
are popular materials in virtue of their fascinating properties such
as metal coordination ability, high refractive indices, and semiconducting
property. The synthesis of sulfur-containing polymers is challenging,
especially directly from elemental sulfur. Herein, catalyst-free and
scalable multicomponent polymerizations (MCPs) of all commercially
available elemental sulfur, dicarboxylic acids, and diamines were
reported to facilely construct 12 polythioamides with diverse and
well-defined structures, high molecular weights (Mw’s up to 86 200 g/mol), and excellent yields
(up to 99%) from elemental sulfur. Besides commonly used aliphatic
diamines, aromatic diamine monomers are also applicable to these multicomponent
polymerizations, affording polythioamides with unique rigid structures
and improved functionality as compared to those of the previously
reported polythioamides. These polythioamides can be applied in gold
recovery, which could extract a trace amount of Au3+ from
practical acidic leaching solution of discarded electronic waste selectively,
rapidly (1 min), sensitively (10 ppb), and efficiently (>99.99%)
with
high extraction capacity up to 0.60 g· Au3+/g to directly
afford high-purity elemental gold after pyrolysis. The MCPs could
make use of both abundantly existing sulfur waste and trace amounts
of precious gold residue in electronic wastes, demonstrating their
great potential in resource utilization.