Bonded type RE3+ doped luminescent co-polymer was synthesized by solution free radical copolymerization. The influence of charge sequence, monomers and co-polymerized method on properties and structures of the co-poly...Bonded type RE3+ doped luminescent co-polymer was synthesized by solution free radical copolymerization. The influence of charge sequence, monomers and co-polymerized method on properties and structures of the co-polymers was studied. The emission intensity of the co-polymers at different RE3+ concentrations was tested. The results showed that the co-polymers of Eu-PSt and Eu-PMMA both had wide absorption peak at 200-400 nm and the strongest peak appeared at 235 nm. The fluorescent intensity of Eu3+ doped polystyrene co-polymer was stronger than that of Eu3+ doped PMMA copolymer. The characteristic emission of europium ions was observed in the co-polymers. The copolymer doped with rare earth elements showed the 'sensitization effect' for the central ions. The bonded-type rare earth copolymer not only enhanced the energy transfer efficiency, but also improved the fluorescence intensity by increasing the rigidity of main and side chain.展开更多
The syndiotactic polymerization of styrene（St） and the copolymerization of St with ethylene（E） were carried out by using a series of chiral half-sandwich rare-earth metal dialkyl complexes（Cp^x＊） as the catalys...The syndiotactic polymerization of styrene（St） and the copolymerization of St with ethylene（E） were carried out by using a series of chiral half-sandwich rare-earth metal dialkyl complexes（Cp^x＊） as the catalysts. The complexes are Ln（CH2SiMe3）2（THF）（1-4： Ln = Sc（1）, Ln = Lu（2）, Ln = Y（3）, Ln = Dy（4）） bearing chiral cyclopentadienyl ligand containing bulky cylcohexane derivatives in the presence of activator and AliBu3. For the St polymerization, a high activity up to 3.1 × 10^6 g of polymer mol Ln^-1·h^-1 and a high syndiotactic selectivity more than 99% were achieved. The resulting syndiotactic polystyrenes（sPSs） have the molecular weights（Mn） ranging from 3700 g·mol^-1 to 6400 g·mol^-1 and the molecular weight distributions（Mw/Mn） from 1.40 to 5.03. As for the copolymerization of St and E, the activity was up to 2.4 × 10^6 g of copolymer mol Sc^-1·h^-1·MPa^-1, giving random St-E copolymers containing syndiotactic polystyrene sequences with different St content in the range of 15 mol%-58 mol%. These results demonstrate that the bulky cyclopentadienyl ligands of the chiral half-sandwich rare-earth metal complexes effectively inhibit the continued insertion of St monomers into the（co）polymer chain to some extent in comparison with the known half-sandwich rare-earth metal complexes.展开更多
The isoprene/ethylene copolymerization catalyzed by cationic rare earth metal complexes [（η5-C5Me5）Sc（CH2SiMe3）]＋ （A） had afforded alternating isoprene-ethylene copolymer with rich 3,4-polyisoprene microstruct...The isoprene/ethylene copolymerization catalyzed by cationic rare earth metal complexes [（η5-C5Me5）Sc（CH2SiMe3）]＋ （A） had afforded alternating isoprene-ethylene copolymer with rich 3,4-polyisoprene microstructures,whereas no isoprene-ethylene copolymer was observed by using analogous [（PNpPh）Nc（CH2SiMe3）]＋ （B） under the same conditions.Theoretical calculations in this work have revealed that,in the case of A,successive 3,4-insertion of isoprene resulted in a noncovalent interaction between the C =C double bond of penultimate unit and the metal center,suppressing the further insertion of monomers due to higher energy barrier and endergonic character.On the other hand,the ethylene pre-inserted species with alkyl active site is more suitable for the subsequent kinetically and thermodynamically favorable isoprene insertion and copolymerization is therefore realized.In the case of B,the experimentally observed cis-l,4-specific homopolymerization of isoprene was the outcome of both kinetic and thermodynamic control.And,the unfavorable ethylene insertion into the isoprene pre-inserted species with allyl active site could account for the experimental finding that no isoprene-ethylene copolymer was obtained.These computational results are expected to provide some hints for the design of rare earth copolymerization catalysts.展开更多
基金Project supported by the Special Funds for Major State Research Projectsthe National Natural Science Foundation of China (50373034)
文摘Bonded type RE3+ doped luminescent co-polymer was synthesized by solution free radical copolymerization. The influence of charge sequence, monomers and co-polymerized method on properties and structures of the co-polymers was studied. The emission intensity of the co-polymers at different RE3+ concentrations was tested. The results showed that the co-polymers of Eu-PSt and Eu-PMMA both had wide absorption peak at 200-400 nm and the strongest peak appeared at 235 nm. The fluorescent intensity of Eu3+ doped polystyrene co-polymer was stronger than that of Eu3+ doped PMMA copolymer. The characteristic emission of europium ions was observed in the co-polymers. The copolymer doped with rare earth elements showed the 'sensitization effect' for the central ions. The bonded-type rare earth copolymer not only enhanced the energy transfer efficiency, but also improved the fluorescence intensity by increasing the rigidity of main and side chain.
基金financially supported by the National Natural Science Foundation of China (Nos. 20974014, 21274012, 21322401 and 21774014)the 111 project (No. B07012)
文摘The syndiotactic polymerization of styrene（St） and the copolymerization of St with ethylene（E） were carried out by using a series of chiral half-sandwich rare-earth metal dialkyl complexes（Cp^x＊） as the catalysts. The complexes are Ln（CH2SiMe3）2（THF）（1-4： Ln = Sc（1）, Ln = Lu（2）, Ln = Y（3）, Ln = Dy（4）） bearing chiral cyclopentadienyl ligand containing bulky cylcohexane derivatives in the presence of activator and AliBu3. For the St polymerization, a high activity up to 3.1 × 10^6 g of polymer mol Ln^-1·h^-1 and a high syndiotactic selectivity more than 99% were achieved. The resulting syndiotactic polystyrenes（sPSs） have the molecular weights（Mn） ranging from 3700 g·mol^-1 to 6400 g·mol^-1 and the molecular weight distributions（Mw/Mn） from 1.40 to 5.03. As for the copolymerization of St and E, the activity was up to 2.4 × 10^6 g of copolymer mol Sc^-1·h^-1·MPa^-1, giving random St-E copolymers containing syndiotactic polystyrene sequences with different St content in the range of 15 mol%-58 mol%. These results demonstrate that the bulky cyclopentadienyl ligands of the chiral half-sandwich rare-earth metal complexes effectively inhibit the continued insertion of St monomers into the（co）polymer chain to some extent in comparison with the known half-sandwich rare-earth metal complexes.
文摘The isoprene/ethylene copolymerization catalyzed by cationic rare earth metal complexes [（η5-C5Me5）Sc（CH2SiMe3）]＋ （A） had afforded alternating isoprene-ethylene copolymer with rich 3,4-polyisoprene microstructures,whereas no isoprene-ethylene copolymer was observed by using analogous [（PNpPh）Nc（CH2SiMe3）]＋ （B） under the same conditions.Theoretical calculations in this work have revealed that,in the case of A,successive 3,4-insertion of isoprene resulted in a noncovalent interaction between the C =C double bond of penultimate unit and the metal center,suppressing the further insertion of monomers due to higher energy barrier and endergonic character.On the other hand,the ethylene pre-inserted species with alkyl active site is more suitable for the subsequent kinetically and thermodynamically favorable isoprene insertion and copolymerization is therefore realized.In the case of B,the experimentally observed cis-l,4-specific homopolymerization of isoprene was the outcome of both kinetic and thermodynamic control.And,the unfavorable ethylene insertion into the isoprene pre-inserted species with allyl active site could account for the experimental finding that no isoprene-ethylene copolymer was obtained.These computational results are expected to provide some hints for the design of rare earth copolymerization catalysts.
