Parameters controlling intrinsic stability and reactivity of organosilanols generated from alkoxysilanes in aqueous environments have been elucidated in several experiments. Data involving kinetics, equilibrium, phase separation, and bonding studies of alkyl and organofunctional alkoxysilanes are presented. The studies indicate that the rates of hydrolysis of alkoxysilanes are generally related to their steric bulk, but demonstrate that after rate-limiting hydrolysis of the first alkoxy group steric effects are much less important. Aqueous hydrolysis of alkylalkoxysilanes was studied to determine equilibrium constants and the extent of oligomerization up to phase separation. In the case of propyltrialkoxysilane, phase separation is coincident with the formation of tetramer. The equilibrium constant for esterification of silanols is Also, the performance properties of new water-borne silanes were evaluated and in most cases, their performance equalled or exceeded their traditional silane counterparts.
Light-emitting diodes are fabricated from regioregular and non-regioregular poly( 3-hexylthiophenes). The regioregular polymer has a higher head-to-tail (HT) ratio than non-regioregular polymer. It is shown that the electroluminescent device containing high HT ratio polymer perform significantly better than polymers with a low HT ratio. Photoluminescence data of both polymers are also reported.
Several years ago, Tang et al. reported observing electroluminescence in diodes in which the emissive layer comprised an organic fluorophore.1 These diodes were composed of at least three layers: (1) a transparent ITO electrode which serves as the anode; (2) an electroactive material, i.e., a fluorophore, that is either dissolved in a polymeric binder and coated from solvent or vacuum evaporated directly onto the anode; (3) a low work function metal cathode such as calcium, magnesium, or aluminum. The utility of additional organic layers for charge injection and confinement was also demonstrated and reported in these patents. In 1989, interest in organic light-emitting diodes intensified when a group of researchers at Cambridge University reported observing electroluminescence from diodes containing poly(phenylenevinylene) (PPV) and its homologues.2 The high level of interest is due to the potential utility of this technology in a wide variety of applications including flat-panel displays.Recent advances for both nonpolymer, i.e., "molecular devices", and polymeric LED's indicate the great poten-
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