In this study, we prepared ordered mesoporous phenolic resins templated by poly(ethylene oxide)-b-(3caprolactone) (PEO-b-PCL) diblock copolymers blended with a star PEO octa-functionalized polyhedral oligomeric silsesquioxane (PEO-POSS) homopolymer. Increasing the PEO-POSS content, and thereby increasing the PEO-to-PCL ratio in the template film, allowed us to tune and enhance the long-range order of the mesoporous phenolic resin. The increased pore size and the more ordered structure were accompanied by a narrower pore size distribution. In addition, we observed an orderedto-ordered mesophase transition, from a bicontinuous gyroid to a hexagonally packed cylinder structure, upon blending with the star PEO-POSS homopolymer. We anticipate that this approach could be extended to the preparation of other large-pore, long-range-ordered mesoporous materials, such as silica and other metal oxides.
This research used the ceric ion to initiate the graftpolymerization of vinyl acetate (VAc) to a soluble potato starch. Fourier transform infrared spectra confirmed the formation of starch graft copolymer. After 4 h of reaction at 508C, total monomer conversion, grafting efficiency, and grafting ratio were measured as 91%, 12.5%, and 0.223, respectively. The synthesized PVAc-modified starch was then blended with poly(3hydroxybutyrate) (PHB). Structures, thermal and mechanical properties of the prepared blends were examined. The results showed the PHB and PVAc-modified starch were miscible in all compositions. In addition, thermal gravimetric analysis revealed that the addition of PVAc-modified starch increased the thermal stability of the PHB component. Further evidence also showed that the addition of PVAc-modified starch reduced the extent of decrease in molecular weight of PHB in a melt-mixer. PHB/PVAc-modified starch blends exhibit higher toughness than pure PHB because of increased compatibility and the leathery PVAc-modified starch.
Deep etching of GaP was performed by high-density plasma using an inductively coupled plasma (ICP) etcher. The effects of process parameters such as the gas combination (Cl-2/N-2), chamber pressure, inductive power and rf chuck power were investigated. The dependences of the etch rates and selectivity on the rf chunk power and chamber pressure were studied using the response Surface method. The results obtained can be further interpreted by the plasma properties (ion flux and de bias) measured in situ by a Langmuir probe. With an increase in the chamber pressure to 4 Pa, a maximum etch rate of similar to7.5 mum/min for GaP can be obtained under a Cl-2/(Cl-2 + N-2) gas mixture of 0.8, ICP power of 800 W, and rf power of 100 W The increase in the etch rate with an increase in chamber pressure indicates that reactive radicals are the main etching species. To clarify the etching mechanism, the surface reaction of GaP under various Cl-2/(Cl-2 + N-2) gas mixtures was investigated by x-ray photoelectron spectroscopy and atomic force microscopy. In addition, quantitative analysis of the plasma-induced damage was attempted in order to discuss the mechanism of leakage current density and brightness with various rf powers on AlGaInP light-emitting diodes with a thick GaP window layer. Under a fixed ICP power applied, it is found that the duration of the plasma (not dc bias voltage) has a major effect on leakage current performance. Finally, an effective recovery method is developed, in which plasma-induced damage can be recovered in a boiling NaOH solution with the range of our experiments. (C) 2002 American Vacuum Society
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