Investigating the Degradability and Optoelectronic Properties of π‑Conjugated Polymers with 1,2,4-Chalcogenadiazole Linkers

As the world is now facing the inevitability of forever
plastics,
all new high-performance polymers require careful design. Building
on our previous work on the degradable 1,2,4-oxadiazole linker for
conjugated polymers, we investigate the effects of chalcogen substitution
in the linker on the optoelectronic and degradation properties of
the π-conjugated polymers. Small molecule models were used to
demonstrate the photodegradation of the linkers in the presence of
methanol. The syntheses of polymers containing 1,2,4-thiadiazole and
1,2,4-selenadiazole linkers by direct heteroarylation polymerization
are reported. As heavier chalcogen atoms are substituted into the
1,2,4-chalcogenadiazole linker, the optical HOMO–LUMO gap becomes
smaller. This effect is due to the stabilization of the HOMO and destabilization
of the LUMO as heavier chalcogen atoms are substituted. The polymers
incorporating the 1,2,4-oxadiazole and 1,2,4-thiadiazole linkers show
evidence of photodegradation by 1H NMR and gel permeation
chromatography.