继高活性茂金属催化体系成功开发以降冰片烯和乙烯共聚物为代表的高性能环烯烃共聚物以来,降冰片烯与其他α-烯烃如丙烯的共聚物研究也备受学术界和工业界的重视。本文介绍了降冰片烯与丙烯共聚合的催化剂和聚合机理等方面的最新研究进...继高活性茂金属催化体系成功开发以降冰片烯和乙烯共聚物为代表的高性能环烯烃共聚物以来,降冰片烯与其他α-烯烃如丙烯的共聚物研究也备受学术界和工业界的重视。本文介绍了降冰片烯与丙烯共聚合的催化剂和聚合机理等方面的最新研究进展,包括各种不同结构的茂金属催化剂催化降冰片烯与丙烯共聚合的特点及其共聚物的结构分析。C2-对称和Cs-对称的茂金属催化剂催化降冰片烯与丙烯共聚合时链转移反应较多,以致催化活性较低,所得的聚合产物分子量偏低。采用限定几何构型茂金属柄型-二甲基亚甲硅基(芴基)(氨基)二甲基钛催化剂进行降冰片烯与丙烯共聚合时,催化活性可高达107 g polymer·(mol cat·h)-1,所得共聚物的相对分子质量超过20万,降冰片烯含量可达70%(mol)且玻璃化转变温度高。展开更多
?Ethene/norbornene copolymerization by the catalyst system [Me_2Si( 3- tertBuCp)(N tertBu)]TiCl_2/MAO was investigated in detail at 30 ℃, 60℃, and 90℃. A mass flow controller was used in this work to obtain kine ...?Ethene/norbornene copolymerization by the catalyst system [Me_2Si( 3- tertBuCp)(N tertBu)]TiCl_2/MAO was investigated in detail at 30 ℃, 60℃, and 90℃. A mass flow controller was used in this work to obtain kine tic data and investigate tempera ture's effects on activity, norbornene incorporation, copolymerization parameter , microstructure, glass transition temperature, and molar masses were described. H igh copolymerization values r_E and high alternation are determined. The n umber of isotactic alternating sequences is much higher than that of the syndiot actic alter nating sequences.展开更多
The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar g...The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comonomers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily accessible,inexpensive,and capable of introducing two functional groups in a single insertion.More importantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to b-hydride elimination due to their cyclic structures.As strong pdonors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palladium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the resulting polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.展开更多
文摘继高活性茂金属催化体系成功开发以降冰片烯和乙烯共聚物为代表的高性能环烯烃共聚物以来,降冰片烯与其他α-烯烃如丙烯的共聚物研究也备受学术界和工业界的重视。本文介绍了降冰片烯与丙烯共聚合的催化剂和聚合机理等方面的最新研究进展,包括各种不同结构的茂金属催化剂催化降冰片烯与丙烯共聚合的特点及其共聚物的结构分析。C2-对称和Cs-对称的茂金属催化剂催化降冰片烯与丙烯共聚合时链转移反应较多,以致催化活性较低,所得的聚合产物分子量偏低。采用限定几何构型茂金属柄型-二甲基亚甲硅基(芴基)(氨基)二甲基钛催化剂进行降冰片烯与丙烯共聚合时,催化活性可高达107 g polymer·(mol cat·h)-1,所得共聚物的相对分子质量超过20万,降冰片烯含量可达70%(mol)且玻璃化转变温度高。
文摘?Ethene/norbornene copolymerization by the catalyst system [Me_2Si( 3- tertBuCp)(N tertBu)]TiCl_2/MAO was investigated in detail at 30 ℃, 60℃, and 90℃. A mass flow controller was used in this work to obtain kine tic data and investigate tempera ture's effects on activity, norbornene incorporation, copolymerization parameter , microstructure, glass transition temperature, and molar masses were described. H igh copolymerization values r_E and high alternation are determined. The n umber of isotactic alternating sequences is much higher than that of the syndiot actic alter nating sequences.
基金the National Natural Science Foundation of China(52025031,21690071,U19B6001,and U1904212)K.C.Wong Education Foundation。
文摘The transition-metal-catalyzed copolymerization of olefins with polar comonomers is a direct strategy to access polar-functionalized polyolefins in an economical manner.Due to the intrinsic poisoning effect of polar groups towards Lewis acidic metal centers and the drastic reactivity differences of polar comonomers versus non-polar olefins,it is challenging to develop catalysts that provide the desired polymer molecular weight,comonomer incorporation,and activity.In this contribution,we tackle this issue from a comonomer perspective using 5,6-disubstituted norbornenes,which are highly versatile,easily accessible,inexpensive,and capable of introducing two functional groups in a single insertion.More importantly,they are only mildly poisoning due to the presence of long spacers between double bonds and polar groups,and are not prone to b-hydride elimination due to their cyclic structures.As strong pdonors,they can competitively bind to metal centers versus olefins.Indeed,phosphine-sulfonate palladium catalysts can catalyze the copolymerization of ethylene with 5,6-disubstituted norbornenes and simultaneously achieve a high polymerization activity,copolymer molecular weight,and comonomer incorporation.The practicality of this system was demonstrated by studying the properties of the resulting polymers,copolymerization in hydrocarbon solvents or in bulk,recovery/utilization of unreacted comonomer,molecular weight modulation,and large-scale synthesis.
