Depolarized dynamic light scattering was used to measure the translational and rotational diffusion of tobacco mosaic virus, TMV, in aqueous solutions of dextran (M ∼505 000). TMV is an electrically charged, nucleoprotein assembly with the shape of a stiff, rigid rod. Dextran is an uncharged, flexible carbohydrate polymer. The TMV was held at a fixed, dilute concentration (0.5 mg/mL), while the concentration of dextran spanned both dilute and semidilute regimes (0−14.5% by weight). There was no evidence of phase separation or strong aggregation of the TMV particles in the presence of the dextran. The TMV particles dominated the depolarized scattering at all dextran concentrations. The angular variation of the decay rates of the autocorrelation functions always followed the form expected for symmetric top molecules in the absence of translational−rotational coupling. Nevertheless, translational and rotational motions are almost surely coupled in most dextran-containing solutions. The apparent translational and rotational diffusion rates decreased with added dextran, but not exactly according to the rise in macroscopic solution viscosity. A transition occurred at about 6.5% dextran. Beyond this concentration, pronounced failures of the continuum (Stokes−Einstein) relation between diffusion and viscosity were found. Translational diffusion continued more rapidly than expected on the basis of the macroscopic viscosity, while rotational diffusion fell sharply below expectation. The quotient D r/D t of rotational and translational diffusion, which presumably cancels effects due to viscosity, also dropped suddenly above the transition point. These findings are consistent with a sudden onset of topological constraints to rotational motion of the TMV, without onset of severe constraints to translational motion. Temperature dependent studies showed that either the solution or the solvent viscosity can describe translation and rotation fairly well, at least at concentrations below the transition. Energies of activation for translational and rotational diffusion of TMV were similar and not strongly dependent on dextran concentration in this regime.

Graphical abstractHighlights► Vacuum-evaporated polyethylene (PE) is a highly stable and trap-free dielectric. ► PE supports low-hysteresis transport in C60 and pentacene. ► PE additionally allows ambipolar transistor operation of 6,6′-dibromoindigo with balanced mobilities of ∼0.3 cm2/Vs. ► This work shows that high-quality gate dielectrics consisting of polymeric materials can be vacuum-processed.

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Polypropylene(PP)/carbon black(CB) composites at different compositions were prepared via melt blending of PP with CB. The effect of CB content on mechanical and electrical properties was studied. Test samples were prepared by injection molding and compression molding techniques. The effect of processing type on mechanical and electrical properties was also investigated. Composites become semi-conductive by addition of 2 wt% CB. The relation between mechanical and electrical properties was discussed. The influence of CB content on morphology and crystallinity was also studied.

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ABSTRACT:The synthesis was performed by the electropolymerization of thiophene on a poly(dimethylsiloxane) (PDMS)-coated platinum electrode at 2.2 V with tetrabutylammoniumtetrafloroborate (TBAFB) as a supporting electrolyte and with acetonitrile as a solvent. The characterization of the PDMS-polythiophene (Pth) composites was carried out with cyclic voltammetry, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis, and conductivity measurements. The observed conductivities of the PDMS composites were 2.2-5.2 S/cm. The conductivity of Pth did not change appreciably with the addition of up to 30% insulating PDMS, but its processability improved. FTIR, SEM, and DSC studies showed the existence of a strong interaction, rather than physical adhesion, between PDMS and Pth. Highly flexible and foldable PDMSPth composites were obtained.

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