Heterogeneous catalysts are used for control of environmental pollution. Heterogeneous catalysts are easily separated from the reaction mixture, thus allowing their recovery and re-use. There is a need for catalysts that are efficient under mild conditions. Here, we show that silicasupported antimony(III) chloride (SbCl 3 /SiO 2 ) acts as a highly efficient heterogeneous Lewis acid catalyst for the Paal-Knorr pyrrole synthesis at room temperature. We found that condensation of hexane-2,5-dione with aromatic and aliphatic primary amines in hexane using SbCl 3 /SiO 2 with 7.6 wt% SbCl 3 was the best reaction condition. The silica support facilitated the workup of the reaction mixture and provided a reusable catalyst at least for 7 runs without significant loss in activity. Indeed, the yield was 98% for the first run and 84% for the 7th run. We conclude that low catalyst loading, operational simplicity, practicability and applicability to various substrates make this reaction an interesting alternative to previously applied procedures. From the environmental standpoint, this eco-friendly catalyst is stable, highly active, easy to prepare and handle.
Hybrids consisting of a microporous film and polymeric microspheres were fabricated via a simple method without a special apparatus. Highly ordered microporous polymer films with honeycomb structure were fabricated by a dissipative process utilizing amphiphilic poly(acrylic acid)block-polystyrene, which was synthesized by atom transfer radical polymerization followed by an acid-catalyzed ester cleavage reaction. In order to embed the microsphere efficiently, the dried microporous films should be soaked in methanol to alter the surface functionality and to improve the wettability of the film surface. The introduction of amino functionality to polystyrene microspheres by seeded polymerization of N,N-dimethylaminoethyl methacrylate drastically improved the embedding efficiency. The effect of open pore size was also investigated.
Microspheres based on binary polymer blend consisting of polystyrene (PSt), poly (methyl methacrylate) (PMMA), block copolymer comprising PSt and PMMA subunits, and ternary polymer blend consisting of PSt, PMMA, and block copolymer were fabricated by a solvent evaporation method, in which a polymer solution in dichloromethane was dispersed in water phase with the aid of a homogenizer to obtain an O/W emulsion followed by solvent evaporation with agitation to solidify the polymer. In the case of ternary blend, the effect of block copolymer content on the morphology of resulting spheres was investigated. Ternary blends afforded the bi-compartmental morphologies, the intermediate morphology between Janus and core-shell, which was confirmed by TEM observation. Seed polymerization of St or MMA was also carried out utilizing the resulting microspheres as seed particles in order to control the shape, and the surface morphology of particles. The particles with snowman-like morphology were obtained by seed polymerization of St using PSt/PMMA binary blend microspheres as seed particles. Surface roughness was controlled by the polymerization of MMA in the block copolymer seed, and that of St in the ternary blend seed.
Micron-sized polymer particles from single poly(4-butyltriphenylamine) (PBTPA) homopolymer, binary polymer blend [PBTPA/poly(methyl methacrylate) (PMMA)], and ternary polymer blend (PBTPA/PBTPA-b-PMMA/PMMA) via a solvent evaporation method, and the surface morphologies and inside structure of resulting particles were investigated. Spherical homopolymer particles with smooth surface were resulted from PBTPA with low molecular weight. In the case of binary blends (PBTPA/PMMA = 1/1), Janus (low molecular weight) and dumbbell (high molecular weight) type morphologies were observed. The particles based on ternary blends containing PBTPA-b-PMMA showed core-shell type morphologies (PMMA; core, PBTPA; shell). Degree of engulfment of PMMArich domain increased with the content of the block copolymer. The decrease of domain size was not observed although the block copolymer had a suitable structure as a compatibilizer for the blend. It was also found that the initial concentration of polymer solution had an effect on the final morphology.
The phase separation of random methacrylate copolymers with the pendant polyhedral oligomeric silsesquioxanes (POSS) moieties was studied. For the random copolymers of the phenyl-substituted POSS methacrylate (PhPOSSMA) and butyl methacrylate (BMA), the layer-like phase-separated structures were obtained from the copolymers with over circa 20 wt % of PhPOSSMA after thermal annealing in the bulk. The copolymers with larger PhPOSSMA content over 40 wt % showed periodic phase-separated structure with the periodic length ranging from 9.0 to 5.1 nm depending on the composition. The phase separation did not occur by solvent annealing in the bulk. On the other hand, no phase-separated structure was formed from the random copolymer with circa 50 wt % of isobutyl-substituted POSSMA (i-BuPOSSMA) and BMA after thermal annealing. In addition, the phase separation did not occur for both of the random copolymers of PhPOSSMA and i-BuPOSSMA with methyl methacrylate. The resulting phase-separated structures were well characterized by using wide-angle X-ray scattering, small-angle X-ray scattering, and transmission electron microscopy image.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.