In this work, 1,8-diazabicyclo[5.4.0]undec-7-ene （DBU）, 1,5-diazabicyclo[4.3.0]-5-nonene （DBN）, and imidazole （MIM）-derived bromide ionic liquids （ILs） were synthesized and used to catalyze the cycloaddition r...In this work, 1,8-diazabicyclo[5.4.0]undec-7-ene （DBU）, 1,5-diazabicyclo[4.3.0]-5-nonene （DBN）, and imidazole （MIM）-derived bromide ionic liquids （ILs） were synthesized and used to catalyze the cycloaddition reactions of carbon dioxide （CO_2） with several kinds of epoxides to form cyclic car- bonates. The DBU derived bromide ionic liquid system was found to have the best catalytic activity among all the tested ILs. The influences of reaction conditions （including temperature, pressure and reaction time） on the reaction of CO_2 to propylene oxide （PO） were studied to show the best conditions of 120℃, 1 MPa, 2.5 h catalyzed by 2 mol% DBU-derived bromide ionic liquid, with the conversion of PO and the selectivity of propylene carbonate （PC） reaching 99% and 99%, respectively. Under the optimum reaction conditions, the ionic liquid system could be reused at least five times without decrease in selectivity and conversion. NMR spectroscopy and DFT calculations were used to reveal the hydrogen-bond interaction between ionic liquids and rea- gent, based on which the reaction mechanism was proposed.展开更多
With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products,the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-ba...With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products,the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century.In present work,the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds,which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications.The bi-to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors,then using freeze-drying to form the final sponges.The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440μm.The sponges had presented the resistance to enzymatic degradation,shape-remaining ability,and reversible compressibility in aqueous environments,which all could be regulated through the functionalities of epoxides.The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higherfunctionality of epoxides would bring higher cross-linking degree.Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors,and improve the compressive strengths and thermal stabilities of sponges.Nevertheless,the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.展开更多
文摘In this work, 1,8-diazabicyclo[5.4.0]undec-7-ene （DBU）, 1,5-diazabicyclo[4.3.0]-5-nonene （DBN）, and imidazole （MIM）-derived bromide ionic liquids （ILs） were synthesized and used to catalyze the cycloaddition reactions of carbon dioxide （CO_2） with several kinds of epoxides to form cyclic car- bonates. The DBU derived bromide ionic liquid system was found to have the best catalytic activity among all the tested ILs. The influences of reaction conditions （including temperature, pressure and reaction time） on the reaction of CO_2 to propylene oxide （PO） were studied to show the best conditions of 120℃, 1 MPa, 2.5 h catalyzed by 2 mol% DBU-derived bromide ionic liquid, with the conversion of PO and the selectivity of propylene carbonate （PC） reaching 99% and 99%, respectively. Under the optimum reaction conditions, the ionic liquid system could be reused at least five times without decrease in selectivity and conversion. NMR spectroscopy and DFT calculations were used to reveal the hydrogen-bond interaction between ionic liquids and rea- gent, based on which the reaction mechanism was proposed.
基金supported by the National Natural Science Foundation of China(No.22078206).
文摘With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products,the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century.In present work,the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds,which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications.The bi-to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors,then using freeze-drying to form the final sponges.The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440μm.The sponges had presented the resistance to enzymatic degradation,shape-remaining ability,and reversible compressibility in aqueous environments,which all could be regulated through the functionalities of epoxides.The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higherfunctionality of epoxides would bring higher cross-linking degree.Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors,and improve the compressive strengths and thermal stabilities of sponges.Nevertheless,the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.
