Thermoelectric Enhancement by Compositing Carbon Nanotubes into Iodine-Doped Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene].

Free-standing iodine-doped composite samples of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with carbon nanotubes (NTs) showed thermoelectric (TE) power factors (PFs) up to 33 μW·m·K after optimizing multiple factors, including: (1) sample fabrication solvent, (2) doping time, (3) average MEH-PPV molecular weight, (4) NT fraction in the composite, and (5) use of single-wall versus multi-wall nanotubes (SWNT and MWNT, respectively). Composite fabrication from halogenated solvents gave the best TE performance after iodine doping times of 2-4 h; performance drops substantially in ∼20 h doped samples. TE performance dropped after at least 24 h of removal from iodine vapor but was fully restored upon re-exposure to the dopant.

One- and two-photon photochemistry and photophysics of poly(arylenevinylene)s containing a biphenyl moiety.

Photochemical and photophysical properties were investigated for poly(arylenevinylene)s containing a flexible biphenyl "hinge" unit by applying one-photon (OP) and two-photon (TP) excitation to explore excited-state properties. The poly(arylenevinylene)s were poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(4,4'-dihexyloxy-3,3'-biphenylenevinylene)] (1), poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-dihexyloxy-3,3'-biphenylenevinylene)] (2), and poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-biphenylenevinylene)] (3). Effective emission quantum yields and related photonic properties were evaluated on a realistic per-chromophore basis using effective conjugation lengths based on the Strickler-Berg relationship.

The aggregation of reverse micelles. A computer simulation.

We have developed a computer simulation to model the formation of reverse micelles in two dimensions. Several of the qualitative results obtained from these calculations agree with experimental observations. Specifically, we have shown that the chain length has a large influence in determining the size and shape of the aggregate.

Conformational transitions of polypeptides in ternary solvent systems.

Phase diagrams for conformational transitions of polypeptides in ternary organic solvent systems containing two active and one inert component are calculated for a model which takes into account possible interaction of the two active components with each other as well as with the polypeptide backbone. The results of experimental determinations of conformational transitions and isothermal phase boundaries for poly(beta-benzyl L-asparate) (PBA) in three-model solvent systems are in generally good accord with the theory. The solvent systems are: (a) 1-chloropropionic acid-dichloroacetic acid (DCA)-1,1,2,2-tetrachloroethane (TCE), (b) monochloroacetic acid-DCA-TCE, and (c) dimethyl sulfoxide-DCA-TCE.