Exploiting α-/ω-Reactivities during Polymerization for Controlled Heterotelechelic Poly(carbazole)s

The preparation of poly(N-alkyl-3,6-carbazole)s with defined alpha-/omega-end groups is investigated using a commercial Buchwald-type pre-catalyst. The applied excess of monofunctional aryl halide favored the Suzuki-Miyaura catalyst-transfer polymerization (SCTP) mechanism, leading to heterotelechelic polymers with defined molar masses, narrow dispersities, and high chemical yields (>85%). Notably, the absence of monofunctional aryl halide leads to quantitative formation of conjugated p-type poly-(carbazole) macrocycles and the formation of longer chains via step-growth. The SCTP conditions lead to quantitative alpha-end group identity and up to 50% omega-end group identity due to the incomplete in situ post-polymerization capping step. The end groups were analyzed in depth by MALDI-ToF mass spectrometry on the basis of isotope simulations and relative end group distributions. The fractionation via preparative SEC yielded isolated polymer batches up to 6000 g/mol, very low dispersity values (<1.1), and confirmed end group identities (alpha: >99%, omega: up to 50%), including reactive azide and/or protected boronic ester end groups.

Automated summary

This study investigates the preparation of poly(N-alkyl-3,6-carbazole)s with defined alpha-/omega-end groups using a commercial Buchwald-type pre-catalyst. It is found that an excess of monofunctional aryl halide favors the Suzuki-Miyaura catalyst-transfer polymerization (SCTP) mechanism, resulting in heterotelechelic polymers with defined molar masses, narrow dispersities, and high chemical yields.