Side chain length affects backbone dynamics in poly(3-alkylthiophene)s

Pengfei Zhan, Wenlin Zhang, Ian E. Jacobs, David M. Nisson, Renxuan Xie, Albree R. Weissen, Ralph H. Colby, Adam J. Moulé, Scott T. Milner, Janna K. Maranas, Enrique D. Gomez

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Charge transport in conjugated polymers may be governed not only by the static microstructure but also fluctuations of backbone segments. Using molecular dynamics simulations, we predict the role of side chains in the backbone dynamics for regiorandom poly(3-alkylthiophene-2,5-diyl)s (P3ATs). We show that the backbone of poly(3-dodecylthiophene-2-5-diyl) (P3DDT) moves faster than that of poly(3-hexylthiophene-2,5-diyl) (P3HT) as a result of the faster motion of the longer side chains. To verify our predictions, we investigated the structures and dynamics of regiorandom P3ATs with neutron scattering and solid state NMR. Measurements of spin-lattice relaxations (T1) using NMR support our prediction of faster motion for side chain atoms that are farther away from the backbone. Using small-angle neutron scattering (SANS), we confirmed that regiorandom P3ATs are amorphous at about 300 K, although microphase separation between the side chains and backbones is apparent. Furthermore, quasi-elastic neutron scattering (QENS) reveals that thiophene backbone motion is enhanced as the side chain length increases from hexyl to dodecyl. The faster motion of longer side chains leads to faster backbone dynamics, which in turn may affect charge transport for conjugated polymers.

Original languageEnglish (US)
Pages (from-to)1193-1202
Number of pages10
JournalJournal of Polymer Science, Part B: Polymer Physics
Issue number17
StatePublished - Sep 1 2018

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry


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