American Chemical Society
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Chiroptical Properties of a Benzotriazole–Thiophene Copolymer Bearing Chiral Ethylhexyl Side Chains

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journal contribution
posted on 2016-12-15, 09:53 authored by Stephanie L. Fronk, Yueqin Shi, Martin Siefrid, Cheng-Kang Mai, Caitlin McDowell, Guillermo C. Bazan
Conjugated polymers containing alternating thiophene units and benzotriazole structural units bearing either chiral (S)-2-ethylhexyl (PBTz-Th*) or racemic 2-ethylhexyl side chains (PBTz-Th) were synthesized. Characterization by optical absorption spectroscopy of both PBTz-Th* and its racemic counterpart reveal aggregated chains, even at dilute concentrations in good solvents. The presence of a chiral substituent permits characterization via circular dichroism (CD) spectroscopy. CD spectra provide evidence of chiral aggregates of PBTz-Th* chains even at 0.01 mg/mL in dichlorobenzene. When PBTz-Th* solutions are diluted with PBTz-Th, the resulting CD spectrum suggests that PBTz-Th* chains are chiral in the aggregate. Chiral ordering is also found to translate from aggregates in solution to the solid state.