Huber Rachel C, Ferreira Amy S, Aguirre Jordan C, Kilbride Daniel, Toso Daniel B, Mayoral Kenny, Zhou Z Hong, Kopidakis Nikos, Rubin Yves, Schwartz Benjamin J, Mason Thomas G, Tolbert Sarah H
Department of Chemistry and Biochemistry, UCLA , Los Angeles, California 90095-1569, United States.
Department of Microbiology, Immunology & Molecular Genetics, and Biomedical Engineering Program, UCLA , 609 Charles E. Young Drive South, Los Angeles, California 90095, United States.
J Phys Chem B. 2016 Jul 7;120(26):6215-24. doi: 10.1021/acs.jpcb.6b02202. Epub 2016 Apr 29.
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.
聚（芴-alt-噻吩）（PFT）是一种共轭聚电解质，在水中自组装成棒状胶束，共轭聚合物主链沿胶束长度方向排列。在适度浓度下（水溶液中约10 mg/mL），PFT形成水凝胶，这项工作重点在于了解这些凝胶网络中的结构和分子间相互作用。网络结构可通过冷冻电子显微镜直接观察。振荡流变学研究进一步向我们揭示了凝胶网络内的连通性，数据与聚合物链在胶束之间桥接以维持网络结构的情况一致。向凝胶中添加四氢呋喃（THF）会破坏这些连接，但一旦去除THF，凝胶会比之前更强，可能是由于形成了更相互连接的纳米级结构。小聚合物低聚物也可使桥接聚合物链钝化，破坏胶束之间的连接并显著削弱水凝胶网络。使用Dammin珠模型对溶液相小角X射线散射数据进行拟合，支持了即使在稀水溶液中PFT胶束之间存在桥接连接的假设。最后，对干燥样品进行的时间分辨微波电导率测量表明，PFT凝胶经THF退火后载流子迁移率增加，这可能是由于聚合物网络内连通性增加所致。
