Stereoregular pendant electroactive polymers with extended pendants via post‐polymerization copper catalyzed azide‐alkyne cycloaddition

Abstract

Recent work on non‐conjugated pendant electroactive polymers (NCPEPs) has demonstrated significant impacts of structural parameters such as backbone stereoregularity and the spacer connecting the pendant to the backbone on properties, most notably on charge carrier mobilities. Tuning of the pendant group however has not been reported for stereoregular NCPEPs. Here we present a family of novel isotactic poly((carbazolyl‐alkyl‐triazolyl)methyl methacrylates) (PCzATMMAs) for which the effects of increasing the pendant group from carbazole to 3,6‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)‐carbazole were investigated. Based on unsuccessful post‐polymerization functionalization with this extended group via previously reported transesterification and thiol‐ene methodologies, we report functionalization via copper‐catalyzed azide‐alkyne cycloaddition which was demonstrated to be highly effective. The effect of spacer length was also investigated for comparison with previously established effects with alkyl spacers. Within the family of PCzATMMAs, hole mobilities were found to increase with longer spacer length and with thermal annealing. The incorporation of an extended pendant with alkyl solubilizing chains was found to result in a lower hole mobility than the equivalent polymer with an unfunctionalized pendant group. Importantly, the copper catalyzed azide‐alkyne cycloaddition proved to be an effective method of post‐polymerization functionalization for stereoregular NCPEPs when extending beyond a simple carbazole pendant.

Stereoselective Polymerization of 3,6-Disubstituted N-Vinylcarbazoles

“…Hole-transport measurements identified a direct relationship between increasing hole conductivity and isotacticityhighlighting the key role polymer stereochemistry can play in tuning electronic properties. − The Lewis acid/Bronsted acid co-catalyst system used to engender isotacticity required cryogenic temperatures, which precluded the polymerization of functionalized vinyl carbazoles due to the solubility of such derivatives . In a complementary strategy, Thompson and co-workers synthesized nonconjugated poly­(methacrylate) polymers that have pendant N- vinyl carbazoles. − Notably, the isotactic polymers demonstrated orders of magnitude higher transport properties than their atactic counterparts . These studies motivate the discovery of synthetic methods to access stereoregular derivatives of diversely substituted PNVCs to enable further structure–property studies …”