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Encapsulation of Poly(3-hexylthiophene) J‑Aggregate Nanofibers with an Amphiphilic Block Copolymer

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journal contribution
posted on 27.11.2012, 00:00 by Jian Gao, Amanda Kamps, So-Jung Park, John K. Grey
Poly­(3-hexylthiophene) (P3HT) nanofibers (NF) displaying J-aggregate exciton coupling behavior are encapsulated with the amphiphilic block copolymer (BCP), poly­(3-hexyl-thiophene)-block-poly­(ethylene-glycol), (PHT20-b-PEG108). Encapsulation results in the formation of hierarchical superstructures, and the BCP coating is expected to exert a mild chemical pressure on the periphery of the NFs. Photoluminescence from encapsulated NF superstructures show line shape distortions due to self-absorption of the 0–0 transition which is consistent with preservation of J-aggregate character (intrachain order). Detailed resonance Raman spectra of encapsulated BCP-NF structures show no discernible changes in the P3HT aggregation state, and overtone and combination bands involving the symmetric stretching CC (∼1450 cm–1) and C–C (∼1380 cm–1) backbone modes are observed. These features permit quantitative estimates of vibrational mode-specific excited state structural displacements using a time-dependent Raman intensity analysis which is not possible from conventional vibronic analysis of optical lineshapes.