Coil-to-Rod Transition of Conjugated Polymers Prepared by Cyclopolymerization of 1,6-Heptadiynes
journal contributionposted on 17.09.2013 by Eun-Hye Kang, Tae-Lim Choi
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We report the conformational change resulting from the coil-to-rod transition in conjugated polymers prepared by the cyclopolymerization of 1,6-heptadiyne derivatives (poly(cyclopentenylene-vinylene), PCPV). By aging a PCPV solution under various conditions, we observed dramatic changes in their absorption spectra (appearance of a 0–0 vibronic peak) and an increase in the Mark–Houwink–Sakurada shape parameter, thereby confirming the coil-to-rod transition of the polymer. Further studies using NMR spectroscopy and various control experiments demonstrated that the coil-to-rod transformation resulted from the cis-to-trans isomerization of the conjugated olefins by a radical mechanism.