Structure and Conductivity of Semiconducting Polymer Hydrogels

Nikos Kopidakis, Rachel Huber, Amy Ferreira, Jordan Aguirre, Daniel Kilbride, Daniel Toso, Kenny Mayoral, Hong Zhou, Yves Rubin, Benjamin Schwartz, Thomas Mason, Sarah Tolbert

Research output: Contribution to journalArticlepeer-review

16 Scopus Citations

Abstract

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that self-assembles into rod-like micelles in water, with the conjugated polymer backbone running along the length of the micelle. At modest concentrations (∼10 mg/mL in aqueous solutions), PFT forms hydrogels, and this work focuses on understanding the structure and intermolecular interactions in those gel networks. The network structure can be directly visualized using cryo electron microscopy. Oscillatory rheology studies further tell us about connectivity within the gel network, and the data are consistent with a picture where polymer chains bridge between micelles to hold the network together. Addition of tetrahydrofuran (THF) to the gels breaks those connections, but once the THF is removed, the gel becomes stronger than it was before, presumably due to the creation of a more interconnected nanoscale architecture. Small polymer oligomers can also passivate the bridging polymer chains, breaking connections between micelles and dramatically weakening the hydrogel network. Fits to solution-phase small-angle X-ray scattering data using a Dammin bead model support the hypothesis of a bridging connection between PFT micelles, even in dilute aqueous solutions. Finally, time-resolved microwave conductivity measurements on dried samples show an increase in carrier mobility after THF annealing of the PFT gel, likely due to increased connectivity within the polymer network.

Original languageAmerican English
Pages (from-to)6215-6224
Number of pages10
JournalJournal of Physical Chemistry B
Volume120
Issue number26
DOIs
StatePublished - 2016

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-66809

Keywords

  • gel networks
  • hydrogels
  • PFT

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