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Non‐conjugated pendant electroactive polymers (NCPEPs) are an emerging class of polymers that offer the potential of combining the desirable optoelectronic properties of conjugated polymers with the superior synthetic methodologies and stability of traditional non‐conjugated polymers. Despite an increasing number of studies focused on NCPEPs, particularly on understanding fundamental structure‐property relationships, no attempts have been made to provide an overview on established relationships to date. This review showcases selected reports on NCPEP homopolymers and copolymers that demonstrate how optical, electronic, and physical properties of the polymers are affected by tuning of key structural variables such as the chemical structure of the polymer backbone, molecular weight, tacticity, spacer length, the nature of the pendant group, and in the case of copolymers the ratios between different comonomers and between individual polymer blocks. Correlation of structural features with improvedπ‐stacking and enhanced charge carrier mobility serve as the primary figures of merit in evaluating impact on NCPEP properties. While this review is not intended to serve as a comprehensive summary of all reports on tuning of structural parameters in NCPEPs, it highlights relevant established structure‐property relationships that can serve as a guideline for more targeted design of novel NCPEPs in the future.

 

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.

 

Recent work has identified surface energy as a key figure of merit in predicting the morphology of bulk heterojunction organic solar cells and organic alloy formation in ternary blend organic solar cells. An efficient way of tuning surface energy in conjugated polymers is by introducing functionalised side chains. Here, we present a systematic study on a family of poly(3-hexylthiophene) (P3HT)-based random copolymers bearing five different functionalised side chains (ester, ether, diether, carbamate, nitrile) prepared by direct arylation polymerization (DArP) in terms of their effectiveness in tuning surface energy. This study also exemplifies the superior functional group tolerance in DArP compared to more traditional polymerization procedures. Water droplet contact angle measurements revealed that especially carbamates are highly effective in tuning surface energy, increasing the surface energy from 21.2 mN m −1 with P3HT to 25.5 mN m −1 and 28.6 mN m −1 in 25% and 50% carbamate functionalized copolymers, respectively. Importantly, by introducing a two-carbon-spacer between the conjugated backbone and the functional group, optical and electronic properties of P3HT could be largely maintained in the copolymers as determined by UV/Vis, cyclic voltammetry and space charge limited current hole mobility. 

Initial reports on the novel Cu-catalyzed direct arylation polymerization (Cu-DArP) stated that it required the use of aryl iodides. Herein, we report the first Cu-DArP methodology using more accessible and practical aryl-bromides with catalytic Cu, leading to a range of conjugated polymers with good molecular weights (up to 17.3 kDa) and an undetectable level of defects.