Ultrahigh molecular weight functionalized isotactic polypropylene(f-UHMW-iPP)through the direct copolymerization of propylene with polar monomers is highly desirable but has not been accessed thus far because it invol...Ultrahigh molecular weight functionalized isotactic polypropylene(f-UHMW-iPP)through the direct copolymerization of propylene with polar monomers is highly desirable but has not been accessed thus far because it involves challenging regio-and stereochemistry along with usually reduced molecular weight.Herein,in contrast to the unsuccessful catalyst strategy,a polar monomer-assisted strategy is used to access the above material.The introduction of O-or S-functionalized long-chain polar olefins into the hafnium-catalyzed copolymerization of propylene(and bulkierα-olefins)significantly increases the copolymer molecular weight with a maximum observed increase of+488%.f-UHMW-iPP and functionalized isotactic poly(α-olefin)s(M_(w)>2000 kDa,[mmmm]:99%)are thus prepared at ambient conditions.The incorporation of 1 mol%of polar monomer improves the surface property and significantly increases the long-sought toughness(860%)of brittle iPP,without reducing the tensile strength(42 MPa)due to the key achievement of ultrahigh molecular weight.A discussion of the mechanism involved in the beneficial effects of incorporating the polar monomer is herein presented by an in-depth density functional theory calculation.展开更多
Coordination polymerization of renewable(E)-4,8-dimethyl-1,3,7-nonatriene(DMNT)has been performed using pyridyl-methylene-fluorenyl scandium complex 1,half-sandwich scandium complex 2,diiminophosphinato rare-earth met...Coordination polymerization of renewable(E)-4,8-dimethyl-1,3,7-nonatriene(DMNT)has been performed using pyridyl-methylene-fluorenyl scandium complex 1,half-sandwich scandium complex 2,diiminophosphinato rare-earth metal complexes 3a—3c and 4a—4b,bis(phosphino)carbazolide yttrium complex 5 andβ-diketiminato yttrium complex 6.Fluorenyl scandium complexes 1 and 2,activated by[Ph3C][B(C6F5)4]and AliBu3,are moderately active and show perfect 1,2-regioselective(1,2>99%).Conversely,asymmetric diiminophophinato complexes 3a—3c promote the DMNT polymerization to produce high trans-1,4 regulated products with the activity trend:Sc<Lu<Y.Complexes 4—6 are virtually inactive for the DMNT polymerization although they are highly active in isoprene polymerization.A diblock copolymer bearing 3,4-polyisoprene block and trans-1,4-poly(DMNT)block is obtained using complex 3c in one-pot reaction.Hydrogenation of trans-1,4-poly(DMNT)affords an elastomer with a T_(g) of–10 ℃.The epoxidation reaction of trans-1,4-poly(DMNT)with 3-chloroperbenzoic acid transfers the pendant double bonds in the cis configuration into the epoxy groups.展开更多
随着纤维素应用领域的不断扩大,通过原子转移自由基聚合(Atom Transfer Radical Polymerization,ATRP)对其进行修饰改性并获得功能材料是当前研究的热点。反应体系从传统的非均相体系发展到均相体系,纤维素基材也从纤维素衍生物逐步转...随着纤维素应用领域的不断扩大,通过原子转移自由基聚合(Atom Transfer Radical Polymerization,ATRP)对其进行修饰改性并获得功能材料是当前研究的热点。反应体系从传统的非均相体系发展到均相体系,纤维素基材也从纤维素衍生物逐步转变为天然纤维素。本文主要综述了纤维素接枝改性的最新研究进展和成果。纤维素衍生物根据不同类别,天然纤维素则依据不同溶解体系分别描述了接枝改性的过程,重点介绍接枝共聚物的特殊性能及其在不同领域的应用,并对其前景进行了预测及展望。展开更多
基金support from the National Natural Science Foundation of China(grant nos.22122110,22171038)the Jilin Provincial Science and Technology Department Program for Distinguished Young Scholars.
文摘Ultrahigh molecular weight functionalized isotactic polypropylene(f-UHMW-iPP)through the direct copolymerization of propylene with polar monomers is highly desirable but has not been accessed thus far because it involves challenging regio-and stereochemistry along with usually reduced molecular weight.Herein,in contrast to the unsuccessful catalyst strategy,a polar monomer-assisted strategy is used to access the above material.The introduction of O-or S-functionalized long-chain polar olefins into the hafnium-catalyzed copolymerization of propylene(and bulkierα-olefins)significantly increases the copolymer molecular weight with a maximum observed increase of+488%.f-UHMW-iPP and functionalized isotactic poly(α-olefin)s(M_(w)>2000 kDa,[mmmm]:99%)are thus prepared at ambient conditions.The incorporation of 1 mol%of polar monomer improves the surface property and significantly increases the long-sought toughness(860%)of brittle iPP,without reducing the tensile strength(42 MPa)due to the key achievement of ultrahigh molecular weight.A discussion of the mechanism involved in the beneficial effects of incorporating the polar monomer is herein presented by an in-depth density functional theory calculation.
基金partially supported by the NSFC(project Nos.51773193,52073275).
文摘Coordination polymerization of renewable(E)-4,8-dimethyl-1,3,7-nonatriene(DMNT)has been performed using pyridyl-methylene-fluorenyl scandium complex 1,half-sandwich scandium complex 2,diiminophosphinato rare-earth metal complexes 3a—3c and 4a—4b,bis(phosphino)carbazolide yttrium complex 5 andβ-diketiminato yttrium complex 6.Fluorenyl scandium complexes 1 and 2,activated by[Ph3C][B(C6F5)4]and AliBu3,are moderately active and show perfect 1,2-regioselective(1,2>99%).Conversely,asymmetric diiminophophinato complexes 3a—3c promote the DMNT polymerization to produce high trans-1,4 regulated products with the activity trend:Sc<Lu<Y.Complexes 4—6 are virtually inactive for the DMNT polymerization although they are highly active in isoprene polymerization.A diblock copolymer bearing 3,4-polyisoprene block and trans-1,4-poly(DMNT)block is obtained using complex 3c in one-pot reaction.Hydrogenation of trans-1,4-poly(DMNT)affords an elastomer with a T_(g) of–10 ℃.The epoxidation reaction of trans-1,4-poly(DMNT)with 3-chloroperbenzoic acid transfers the pendant double bonds in the cis configuration into the epoxy groups.
文摘随着纤维素应用领域的不断扩大,通过原子转移自由基聚合(Atom Transfer Radical Polymerization,ATRP)对其进行修饰改性并获得功能材料是当前研究的热点。反应体系从传统的非均相体系发展到均相体系,纤维素基材也从纤维素衍生物逐步转变为天然纤维素。本文主要综述了纤维素接枝改性的最新研究进展和成果。纤维素衍生物根据不同类别,天然纤维素则依据不同溶解体系分别描述了接枝改性的过程,重点介绍接枝共聚物的特殊性能及其在不同领域的应用,并对其前景进行了预测及展望。
