2478-10-6Relevant articles and documents
Enzyme-induced formation of thermoreversible micellar gels from aqueous solutions of multiresponsive hydrophilic ABA triblock copolymers
Woodcock, Jeremiah W.,Jiang, Xueguang,Wright, Roger A. E.,Zhao, Bin
, p. 5764 - 5775 (2011)
We report on the synthesis of thermo- and enzyme-responsive hydrophilic ABA triblock copolymers, poly(ethoxydi(ethylene glycol) acrylate-co-4- ((dihydroxyphosphoryl)oxy)butyl acrylate)-b-poly(ethylene oxide)-b- poly(ethoxydi(ethylene glycol) acrylate-co-4-((dihydroxyphosphoryl)oxy)butyl acrylate) (P(DEGEA-co-OPBA)-b-PEO-b-P(DEGEA-co-OPBA)), and the enzyme-induced formation of thermoreversible micellar gels from their moderately concentrated aqueous solutions at 37 °C. PDEGEA is a thermosensitive water-soluble polymer with a lower critical solution temperature (LCST) at 9 °C in water. The block copolymers were prepared by atom transfer radical polymerization of DEGEA and 4-((di-tert-butoxyphosphoryl)oxy)butyl acrylate and subsequent removal of tert-butyl groups. To seek optimal conditions for enzymatic gelation of aqueous solutions of triblock copolymers, a study of dephosphorylation of a random copolymer P(DEGEA-co-OPBA) by acid phosphatase in water at 37 °C was carried out. The time for the solution to turn cloudy was found to decrease with the decrease of pH from 5.48 to 4.70 and level off from pH 4.39 to 4.23. The cleavage of phosphate groups made the polymer less hydrophilic and decreased the LCST from above to below 37 °C. Therefore, pH 4.4 was selected to conduct the enzyme-induced gelation of 7.9 wt % aqueous solutions of P(DEGEA-co-OPBA)-b-PEO-b-P(DEGEA-co-OPBA). The gelation processes were monitored by rheological measurements; the sol-gel transition temperature decreased and the gel strength increased with the increase of reaction time. The gels formed were thermoreversible; lowering temperature converted the gels to free-flowing liquids. From 1H and 31P NMR spectroscopy analysis, the degree of dephosphorylation was high. The formation of three-dimensional micellar network gels stemmed from the thermosensitive properties of the resultant dephosphorylated triblock copolymers, which was confirmed by a dynamic light scattering study. At a slightly higher pH (4.67), the enzyme-induced gelation was significantly slower, consistent with the observation of the effect of pH on dephosphorylation of the random copolymer by acid phosphatase.
Runge-Kutta analysis for optimizing the Zn-catalyzed transesterification conditions of MA and MMA with diols to maximize monoesterified products
Akebi, Shin-Ya,Kato, Taito,Mashima, Kazushi,Nagae, Haruki,Oku, Tomoharu,Yonehara, Koji
, p. 6975 - 6986 (2021/11/17)
Terminal hydroxylated acrylates and methacrylates were prepared by catalytic transesterification of acrylates and methacrylates with diols catalyzed by a system of a tetranuclear zinc alkoxide, [Zn(tmhd)(OMe)(MeOH)]4 (1a), with 4 equiv. of 2,2′-bipyridine (L1). The reaction time to reach the equilibrium state was analyzed by kinetic studies and a curve-fitting analysis based on the Runge-Kutta method for optimizing the best reaction conditions for mono-esterification. In addition to these kinetic analyses, DFT calculations estimated a proposed mechanism of the catalytic transesterification. This journal is
Oxidative Deprotection of p-Methoxybenzyl Ethers via Metal-Free Photoredox Catalysis
Ahn, Deok Kyun,Kang, Young Woo,Woo, Sang Kook
, p. 3612 - 3623 (2019/03/11)
An efficient and greener deprotection method for p-methoxybenzyl (PMB) ethers using a metal-free visible light photoredox catalyst and air and ammonium persulfate as the terminal oxidants is presented. Various functional groups and protecting groups were tolerated in the developed method to achieve good to excellent yields in short reaction times. Significantly, the developed method was compatible with PMB ethers derived from primary, secondary, and tertiary alcohols and a gram-scale reaction. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of the PMB ether.
