Structure and Conductivity of Semiconducting Polymer Hydrogels

Journal Article · Thu Apr 14 00:00:00 EDT 2016 · Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry

DOI:https://doi.org/10.1021/acs.jpcb.6b02202· OSTI ID:1370241

Huber, Rachel C. ^[1]; Ferreira, Amy S. ^[1]; Aguirre, Jordan C. ^[1]; Kilbride, Daniel ^[1]; Toso, Daniel B. ^[1]; Mayoral, Kenny ^[1]; Zhou, Z. Hong ^[1]; Kopidakis, Nikos ^[2]; Rubin, Yves ^[1]; Schwartz, Benjamin J. ^[1]; Mason, Thomas G. ^[1]; Tolbert, Sarah H. ^[1]

---

1. Univ. of California, Los Angeles, CA (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that typically 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. Lastly, 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.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Molecularly Engineered Energy Materials (MEEM)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Institutes of Health (NIH); National Science Foundation (NSF)
• Grant/Contract Number: SC0001342; AC02-76SF00515
• OSTI ID: 1370241
• Journal Information: Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry, Vol. 120, Issue 26; Related Information: MEEM partners with University of California, Los Angeles (lead); University of California, Berkeley; Eastern Washington University; University of Kansas; National Renewable Energy Laboratory; ISSN 1520-6106
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY