Structure and Conductivity of Semiconducting Polymer Hydrogels.

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.

POLARON DYNAMICS. Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies.

The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.

Computerized self-monitoring and technology-assisted feedback for weight loss with and without an enhanced behavioral component.

OBJECTIVE: The purpose of this study was to develop and evaluate a 12-week weight management intervention involving computerized self-monitoring and technology-assisted feedback with and without an enhanced behavioral component. METHODS: 120 overweight (30.5±2.6kg/m(2)) adults (45.0±10.3 years) were randomized to one of three groups: computerized self-monitoring with Basic feedback (n=45), Enhanced behavioral feedback (n=45), or wait-list control (n=30). Intervention participants used a computer software program to record dietary and physical activity information. Weekly e-mail feedback was based on computer-generated reports, and participants attended monthly measurement visits. RESULTS: The Basic and Enhanced groups experienced significant weight reduction (-2.7±3.3kg and -2.5±3.1kg) in comparison to the Control group (0.3±2.2; p<0.05). Waist circumference and systolic blood pressure also decreased in intervention groups compared to Control (p<0.01). CONCLUSIONS: A program using computerized self-monitoring, technology-assisted feedback, and monthly measurement visits produced significant weight loss after 12 weeks. However, the addition of an enhanced behavioral component did not improve the effectiveness of the program. PRACTICE IMPLICATIONS: This study suggests that healthcare professionals can effectively deliver a weight management intervention using technology-assisted strategies in a format that may complement and reduce face-to-face sessions.