Larry Neil Lewis

Solution-Processed Organic Light-Emitting Diodes for Lighting

In this paper, the vapor-deposited and solution-processed organic light-emitting diode (OLED) technology development paradigms are described and then compared with respect to their prospects for enabling general lighting applications. Two key development needs are improved device efficiency and lower cost fabrication methods. Progress in these areas for solution-processed OLEDs is illustrated by describing recent methods for attaining high efficiency blue emission and introducing novel low cost process methods for device fabrication which enable high performance devices without the need for any vacuum processing steps

Aminosilicone Solvents for CO2 Capture

This work describes the first report of the use of an aminosilicone solvent mix for the capture of CO(2). To maintain a liquid state, a hydroxyether co-solvent was employed which allowed enhanced physisorption of CO(2) in the solvent mixture. Regeneration of the capture solvent system was demonstrated over 6 cycles and absorption isotherms indicate a 25-50 % increase in dynamic CO(2) capacity over 30 % MEA. In addition, proof of concept for continuous CO(2) absorption was verified. Additionally, modeling to predict heats of reaction of aminosilicone solvents with CO(2) was in good agreement with experimental results.

Metal colloid morphology and catalytic activity : further proof of the intermediacy of colloids in the platinum-catalyzed hydrosilylation reaction

Abstract Transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) were used to analyze the platinum colloids formed during hydrosilylation reactions. Reaction solutions were analyzed for the addition of Et3SiH to either n-hexene or neohexene catalyzed by bis{1,3diviny1,1,1,3,3-tetramethyldisiloxane}Pt0 (Karstedts catalyst) and this analysis showed dramatic differences between the morphology of the Pt colloid formed in each case. The neohexene reaction, which gave 62% conversion to products in 1 h, contained polycrystalline, 2.5-nm-diameter Pt particles, whereas the n-hexene reaction only went to 10% conversion in 1 h and contained 1- to 1.5-nm Pt particles. The reaction of Et3SiH with styrene gave results similar to those with neohexene.

The chemistry of fumarate and maleate inhibitors with platinum hydrosilylation catalysts

Abstract Pt(MviMvi)x (MviMvi = 1.3-divinyltetramethyl disiloxane), 1, was reacted with dimethyl fumarate to give 2. Compound 2 was investigated by 1H and 13C NMR spectroscopy which showed it to be a mono-nuclear platinum compound containing one dimethyl fumarate and one chelating MviMvi ligand. The reaction of 1 with dimethyl maleate gave 3 which was analogous in structure to the fumarate product as shown by 1H and 13C NMR spectroscopy and extended X-ray absorption fine structure spectroscopy (EXAFS). The EXAFS analysis showed the presence of Pt-C bonds and a through space close contact between Pt and the O from the carbonyl. The NMR assignments were confirmed by comparing the NMR spectra of 2 and 3 with that of (PPh3)Pt(MviMvi), 4. Reaction of 2 or 3 with an excess of an SiH-containing compound (either MDHDHM (MDHDHM = 1,3-bis(trimethylsiloxy)-1,3-dimethylsiloxane) or Et3SiH) gave 5 in all cases. Compound 5 contains an alkyl succinate ligand. Hydrogenation of the fumarate ligand (of 2) or of the maleate ligand (of 3) occurs by reaction with SiH; 5 appears to be an intermediate in the hydrogenation process. The reaction between 4, dimethylmaleate, and MDHDHM also gives dimethyl succinate. Differential scanning calorimetry was used to compare the effectiveness of the inhibitors in a curable formulation composed of vinyl-stopped-polydimethyl siloxane, polydimethylsiloxanemethylhydrogen-copolymer, a platinum catalyst and either a maleate or fumarate inhibitor.

Mechanistic studies of platinum-catalyzed hydrosilylation

The results of competitive and relative rate studies for various silicon hydrides and vinylmethylsiloxane compounds are presented. For example, the competitive reaction of bis(trimethylsiloxy)methylsilane with vinylpentamethyldisiloxane (A) and divinyltetramethyldisiloxane (B) show that B reacts preferentially; however, the relative rate of reaction is greater for A than B. Mechanistic aspects of hydrosilylation are also discussed.

The effect of metal colloid morphology on catalytic activity: Further proof of the intermediacy of colloids in the rhodium-catalyzed hydrosilylation reaction

Abstract The relative activity of different morphological forms of Rh colloids were examined by transmission electron microscopy (TEM) or high resolution electron microscopy (HREM). The degree of agglomeration of the Rh colloid was affected by either its storage history (e.g. refrigerator or bench top) or by the use of a vinyl silicone stabilizer. The smaller particle size (higher surface area) yellow Rh colloid was more active than the larger particle size red Rh colloid. A black Rh colloid, which contained no stabilizer, was more active than both the yellow and red forms. The heterogeneous nature of both Pt and Rh catalyzed reactions was further confirmed by inhibition studies with mercury.

Hydrosilylation catalysts derived from cyclodextrin organometallic platinum inclusion compounds and their use in command-cure applications

Beta-cyclodextrin (β-CD) complexes of CODPtX2 (COD=1.5-cyclooctadiene.X=Cl, Br, and I) have been prepared and employed as hydrosilylation catalysts. When used in cross-linkable, silicone-containing systems, these catalysts provide a long shelf stability at ambient temperature but cure rapidly at elevated temperature. These systems thus have the property of “command-cure”. Extensive analytical investigations were undertaken to develop reproducible synthetic methodology for the preparation of inclusion compounds free of surface contamination of the guest platinum compound. Water plays a key role in the synthesis of such platinum inclusion compounds. Dried β-CD CODPtX2 compounds can be washed with organic solvent to remove residual uncomplexed CODPtX2, while organic solvent washing of wet inclusion compounds results in removal of the guest from the β-CD cavity. Examination of these catalysts in curable silicone systems is described.

Platinum-group metal cyclodextrin complexes and their use as command-cure catalysts in silicones

The Command-Cure concept is defined for a curable formulation as one with long work-like at ambient temperature and rapid cure time at elevated temperature. This concept is explored for a curable silicone system, cured via hydrosilylation. CODMCl2 complexes (COD=1.5-cyclo-octadiene:M=Pt. Pd) are reacted with beta-cyclodextrin (β-CD) to make 1∶1 inclusion compounds,M=Pd.2;M=Pt.4. Compounds2 and4 were analyzed by1H NMR and X-ray powder diffraction. Their catalytic ability was evaluated in a model system as well as a polymeric system that gels upon cure. Surprisingly, the Pd analog2 was a good command-cure catalyst whereas the guest compound CODPdCl2,1, was not active in the hydrosilylation reaction. The Pt analog,4, was an effective command-cure catalyst while the corresponding guest. CODPtCl2,3, was too active at low temperature in the hydrosilylation reaction. Additional Pt compounds and one Rh inclusion compound were evaluated as command cure catalysts. These inclusion compounds were: 1∶1 β-CD:[CODRhCl]2,5: 1∶1 β-CD:CpPtMe3,6 (Cp=cyclopentadienyl): 1∶2 β-CD:MeCpPtMe3,7; 1∶2 β-CO:CODPtMe2,8. The effectiveness of4 8 was evaluated in a number of silicone systems.

High performance organic light-emitting diodes fabricated via a vacuum-free lamination process

We demonstrate high performance organic light-emitting diodes (OLEDs) fabricated via a vacuum-free, direct lamination process. The OLEDs were made by laminating an anode component to a separately engineered cathode component using a roll laminator. We further present a solution-based chemical n-doping strategy to enable efficient electron injection from an inert cathode into polymeric organic semiconductors. The n-doping strategy is demonstrated by chemically reducing a conjugated light-emitting polymer with an alkali metal in an organic solvent. The metal reduced conjugated polymer, when employed as an electron injection layer, yields laminated OLEDs with efficiency comparable to conventionally fabricated devices utilizing a vacuum-deposited, reactive metal cathode. These designs and techniques should enable applications such as lighting where extremely low cost device fabrication is required.

Platinum catalysed hydrosilylation of alkynes: Comparison of rates of addition of terminal olefins to internal alkynes

The relative rates of platinum catalysed hydrosilytalion of terminal olefins versus internal alkynes were compared in competitive reactions. (EtO)3SiH added almost exclusively (97%) to PhCCPh versus styrene. The reaction of (EtO)3SiH with equimolar amounts of 2-decyne and 1-hexene gave a 78:22 ratio of alkyne products 6/6′ versus alkene product 7. The reaction of (EtO)3SiH with equimolar amounts of styrene and 1-phenyl-1-propyne gave a 78:22 ratio of alkyne products 10/10′ to products 9. The silane, Me3SiOSiMe2H, reacted with equimolar amounts of 2-decyne and 1-hexene to give a 90: 10 ratio of alkyne products 8/8′ to alkene product 9. All of the products had E stereochemistry about the CC double bond as determined by 29Si NMR (3J(Si-H)).