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The effect of plasticizer species and the degree of hydrolysis (DH) on the free volume properties of poly(vinyl alcohol) (PVA) were studied using positron annihilation lifetime spectroscopy. Both glycerol and propylene glycol caused an increase in the free volume cavity radius, although exhibited distinct plasticization behavior, with glycerol capable of occupying existing free volume cavities in the PVA to some extent. The influence of water, normally present in PVA film under atmospheric conditions, was also isolated. Water added significantly to the measured free volume cavity radius in both plasticized and pure PVA matrices. Differences in plasticization behavior can be attributed to the functionality of each plasticizing additive and its hydrogen bonding capability. The increase in cavity radii upon plasticizer loading shows a qualitative link between the free volume of voids and the corresponding reduction in Tg and crystallinity. Cavity radius decreases with increasing DH, due to PVA network tightening in the absence of acetate groups. This corresponds well with the higher Tg observed in the resin with the higher DH. DH was also shown to impact the plasticization of PVA with glycerol, indicating that the larger cavities—created by the weaker hydrogen bonding acetate groups—are capable of accommodating glycerol molecules with negligible effect on the cavity dimensions.

Organic semiconductors have attracted considerable attention due to their applications in low-cost (opto)electronic devices. Many successful organic materials utilize blends of several types of molecules that contribute different functions (e.g., serving as donors and acceptors in solar cells). In blends, the local environment, which is inherently heterogeneous, strongly influences the (opto)electronic performance and photostability. We use functionalized fluorinated pentacene (F8 TCHS-Pn) molecules as single-molecule probes of the nanoscale environment in blends containing donor and acceptor molecules incorporated into a polymer (PMMA) matrix. Single F8 TCHS-Pn donor (D) molecules were imaged in PMMA in the presence of functionalized indenofluorene (TIPS-IF) or PCBM acceptor (A) molecules using wide-field fluorescence microscopy at various concentrations. Long-lived dark states attributed to a reversible formation of an endoperoxide (TCHS-EPO) were observed, and the EPO formation and reversal processes, which evolved upon acceptor addition, were quantified. Our study provides a nanoscale-level insight into how the presence of acceptor molecules alters the photophysics of the donor molecules dispersed in the polymer. Kinetics of the F8 TCHS-Pn photo-oxidation reaction and its reversal in such blends are determined by a fine balance of the acceptor-modified morphology (which in our case speeds up the photo-oxidation and slows down its reversal) and singlet oxygen quenching by acceptors (which prevents repeated photo-oxidation/reversal events).

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The partial molal free energy of mercury in some mercurides has been calculated from the measured values of the electromotive force of amalgam concentration cells.4. The values for the partial molal free energy of mercury in sodium and lead mercurides were found to be -61 and -12 calories, respectively.5. The free energies of formation of sodium and lead mercurides are -18,351 and -280 calories, respectively.6. The partial molal free energies of the constituents of mixed crystals of zinc-mercury, cadmium-mercury and thallium-mercury crystals have been tabulated.7. With the exception of thallium, it has been found in the case of the mercurides and the mixed crystals studied, that the change in free energy has been greater for the electropositive metals than for mercury.Cambridge 39, Massachusetts

Nov., 1923 catalysis of hydrogen peroxide by iron salts 2493 react with potassium iodide or with iodine have been shown to have sensitizing effects.7. An emulsion having no excess of silver nitrate or potassium iodide has been prepared and found to be sensitive. 8. Washing to remove the excess of potassium iodide does not make the regular iodide emulsion sensitive.9. The amount of moisture present in the emulsion has been shown to have considerable effect on the sensitiveness. 10. In general, sensitization has been effected by treatment with a chemical which would react with potassium iodide to remove it, or remain in the emulsion to combine with any iodine liberated.11. The ' ' non-sensitive' ' emulsions have been found to be sensitive when a strongly alkaline developer was employed.12. It is concluded that the apparent non-sensitiveness of silver iodide emulsions is due primarily to adsorbed potassium iodide, secondarily to the absence of a sensitizer, gelatin not playing that role; and that ordinary, apparently non-sensitive, silver iodide emulsions are truly sensitive when a sufficiently strongly alkaline developer is used.

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