Well-defined polycarbonate diol was successfully synthesized through a strategy using a combination of organocatalyst and water.Such strategy was less developed in organocatalyzed polymerization and frequently regarde...Well-defined polycarbonate diol was successfully synthesized through a strategy using a combination of organocatalyst and water.Such strategy was less developed in organocatalyzed polymerization and frequently regarded as side reactions.Herein,one-component phosphonium borane Lewis pairs PB1-PB8 were successfully applied in the copolymerization of CO_(2) and cyclohexene oxide(CHO)to generate poly(CHO-alt-CO_(2))carbonate(PCHC).Parameters of linker length and counter anion effects on the catalyst activity were investigated.It was found that Lewis pair PB3 served as a dual initiator and catalyst in the copolymerization of CHO and CO_(2) with or without the presence of water.In contrast,Lewis pair PB8 can serve as a true catalyst for the preparation of well-definedα,ω-hydroxyl PCHC diols.This was achieved by introducing a labile CF3COO group as counter anion through anion exchange reaction while water molecules acted as chain transfer agents.The function of trifluoroacetate group in the polymerization process was investigated in detail and possible mechanism was proposed.Upon changing the amount of water and catalyst loading,PCHC diols with varied molecular weight(1.5 kg/mol to 7.5 kg/mol),low dispersities(D<1.2)and carbonate content(>99%)could be easily obtained.The low molecular weight PCHC diol was used as a bifunctional macroinitiator for the ring-opening polymerization of L-lactide(LLA)to afford ABA triblock copolymer in one-pot synthesis.展开更多
It is impossible to overstate the importance of energy.Just thinking about where humanity would be without it may be enough to demonstrate this point.Like in the past,energy will play a vital role in shaping future in...It is impossible to overstate the importance of energy.Just thinking about where humanity would be without it may be enough to demonstrate this point.Like in the past,energy will play a vital role in shaping future industries,cities,nations,and the world.That is why we believe that energy is a critical factor in shaping future paradigms in any target entity or world.To have a better understanding of the role that energy plays in the world today and in the future,in this article,we briefly look at the definition of energy and its different forms,and review some data related to energy consumption in the world and the United States.Furthermore,as a source of clean energy,we believe the future of nuclear power technology,despite the challenges it faces,is an important option for this country and the rest of the world to meet future energy needs without emitting CO(carbon monoxide)and CO2(carbon dioxide),or other GHGs(greenhouse gases),and other atmospheric pollutants and it is more efficient among its other comparable sources of renewable energies,such as solar,wind,etc.Globally,renewables made up 29 percent of electricity generation in 2020,much of it from hydro-power(16.8 percent).A record amount of over 256 GW of renewable power capacity was added globally during 2020 and continues to be the focal point for climate and energy solutions.Demand for electricity is direct function of population growth globally and is also driven by the present century’s extraordinary technological developments.展开更多
基金financially supported by the National Key R&D Program of China(No.2021YFA1501600)the National Natural Science Foundation of China(Nos.22175105 and 22031005)。
文摘Well-defined polycarbonate diol was successfully synthesized through a strategy using a combination of organocatalyst and water.Such strategy was less developed in organocatalyzed polymerization and frequently regarded as side reactions.Herein,one-component phosphonium borane Lewis pairs PB1-PB8 were successfully applied in the copolymerization of CO_(2) and cyclohexene oxide(CHO)to generate poly(CHO-alt-CO_(2))carbonate(PCHC).Parameters of linker length and counter anion effects on the catalyst activity were investigated.It was found that Lewis pair PB3 served as a dual initiator and catalyst in the copolymerization of CHO and CO_(2) with or without the presence of water.In contrast,Lewis pair PB8 can serve as a true catalyst for the preparation of well-definedα,ω-hydroxyl PCHC diols.This was achieved by introducing a labile CF3COO group as counter anion through anion exchange reaction while water molecules acted as chain transfer agents.The function of trifluoroacetate group in the polymerization process was investigated in detail and possible mechanism was proposed.Upon changing the amount of water and catalyst loading,PCHC diols with varied molecular weight(1.5 kg/mol to 7.5 kg/mol),low dispersities(D<1.2)and carbonate content(>99%)could be easily obtained.The low molecular weight PCHC diol was used as a bifunctional macroinitiator for the ring-opening polymerization of L-lactide(LLA)to afford ABA triblock copolymer in one-pot synthesis.
文摘It is impossible to overstate the importance of energy.Just thinking about where humanity would be without it may be enough to demonstrate this point.Like in the past,energy will play a vital role in shaping future industries,cities,nations,and the world.That is why we believe that energy is a critical factor in shaping future paradigms in any target entity or world.To have a better understanding of the role that energy plays in the world today and in the future,in this article,we briefly look at the definition of energy and its different forms,and review some data related to energy consumption in the world and the United States.Furthermore,as a source of clean energy,we believe the future of nuclear power technology,despite the challenges it faces,is an important option for this country and the rest of the world to meet future energy needs without emitting CO(carbon monoxide)and CO2(carbon dioxide),or other GHGs(greenhouse gases),and other atmospheric pollutants and it is more efficient among its other comparable sources of renewable energies,such as solar,wind,etc.Globally,renewables made up 29 percent of electricity generation in 2020,much of it from hydro-power(16.8 percent).A record amount of over 256 GW of renewable power capacity was added globally during 2020 and continues to be the focal point for climate and energy solutions.Demand for electricity is direct function of population growth globally and is also driven by the present century’s extraordinary technological developments.
