Poly （methyl methacrylate） （PMMA） brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization （SI-ATRP）. Energy disperse spectroscopy （EDS） and atomic force microsco...Poly （methyl methacrylate） （PMMA） brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization （SI-ATRP）. Energy disperse spectroscopy （EDS） and atomic force microscopy （AFM） confirmed that PMMA brushes were successfully prepared on the silicon wafers, and the surface became more hydrophobic according to the contact angle of 69~. It is found that CuCI/1, 1, 4, 7, 10, 10-hexamethyl triethylenetetramine （HMTETA） system is more suitable than CuBr/N, N, N′, N″, N′″-pentamethyl diethylenetriamine （PMDETA） system to control the free radical polymerization of MMA in solution. Nevertheless, better control on the thickness of PMMA brushes was achieved in CuBr/PMDETA than in CuC1/HMTETA due to higher activity and better reversibility of the former system.展开更多
Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst system of Nd(O? Pr) 3 in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concent...Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst system of Nd(O? Pr) 3 in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concentration, catalyst aging time, solvents, the third component CCl 4, temperature and time on the polymerization of MMA were studied. The results showed that the polymerization conversion reached more than 80% at a catalyst concentration of 9 2×10 -3 mol/L. The appropriate molar ratio of CCl 4/Nd was 4. Hydrocarbon was preferred for the polymerzation to obtain a high conversion and a high M W of PMMA. The 1H NMR spectra of PMMA indicated that the lower the temperature, the higher the syndiotactic content of PMMA was obtained.展开更多
Methyl methacrylate （MMA） was polymerized by using of benzoyl peroxide （BPO） and N, N-dimethylaniline （DMA） as an redox initiator in fluorous triphasic system at room temperature. The polymerization was occurred...Methyl methacrylate （MMA） was polymerized by using of benzoyl peroxide （BPO） and N, N-dimethylaniline （DMA） as an redox initiator in fluorous triphasic system at room temperature. The polymerization was occurred in both initiator layer and monomer layer in a U-tube. It was found that PMMA obtained from the initiator layer with relatively narrow polydispersity.（PDI = 1.38）展开更多
Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)_3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propag...Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)_3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as R_p=K_p[c][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with c_I=3. 6 × 10^(-4).展开更多
Two types of salicylaldiminato-based nickel complexes,mono-ligated Ni(II)complexes([O-C_(6)H_(4)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(5),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(6),[O-(3-t-Bu)C_(6)H_(3)-o-C(H)=N-A...Two types of salicylaldiminato-based nickel complexes,mono-ligated Ni(II)complexes([O-C_(6)H_(4)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(5),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(6),[O-(3-t-Bu)C_(6)H_(3)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(7))and bis-ligated Ni(II)complexes([O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]_(2)Ni(8),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-2-C_(6)H_(4)(PhO)]_(2)Ni(9),Ar=2,6-C_(6)H_(3)(i-Pr)_(2))were synthesized and characterized by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(NMR),mass spectrography(MS)and elemental analysis(EA).In the presence of methylaluminoxane(MAO)as cocatalyst,all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate(MMA)and syndiotactic-rich poly(methyl methacrylate)(PMMA)was obtained.The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities,while with the same salicylaldiminato,the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.展开更多
The polymerization of MMA by coordination catalyst of Nd(naph) 3 Al(i Bu) 3 α,α’ Dipyridyl was described in this paper.Characterization of the structure of the polymer is revealed by NMR and IR.These studies reveal...The polymerization of MMA by coordination catalyst of Nd(naph) 3 Al(i Bu) 3 α,α’ Dipyridyl was described in this paper.Characterization of the structure of the polymer is revealed by NMR and IR.These studies revealed that the polymer obtained has mainly syndiotactic and shetero structures.Molecular weight and distribution are studied by GPC.Coordinate mechanism was proposed for the MMA polymerization by Nd Al α,α’ Dipyridyl.Kinetic studies showed that the MMA polymerization rate is first order with respect to monomer concentration.The apparent activation energy of MMA polymerization reaction is 22.2 kJ/mol.展开更多
基金Project(21376271)supported by the National Natural Science Foundation of ChinaProject(2013)supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,China+2 种基金Projects(CL12129,201310533008)supported by the Undergraduates Innovative Training Foundation of Central South University,ChinaProject(Z12060)supported by the Undergraduate Free Exploration Innovation Foundation of Central South University,ChinaProject(CSUZC2013008)supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
文摘Poly （methyl methacrylate） （PMMA） brushes were synthesized from silicon wafers via surface initiated atom transfer radical polymerization （SI-ATRP）. Energy disperse spectroscopy （EDS） and atomic force microscopy （AFM） confirmed that PMMA brushes were successfully prepared on the silicon wafers, and the surface became more hydrophobic according to the contact angle of 69~. It is found that CuCI/1, 1, 4, 7, 10, 10-hexamethyl triethylenetetramine （HMTETA） system is more suitable than CuBr/N, N, N′, N″, N′″-pentamethyl diethylenetriamine （PMDETA） system to control the free radical polymerization of MMA in solution. Nevertheless, better control on the thickness of PMMA brushes was achieved in CuBr/PMDETA than in CuC1/HMTETA due to higher activity and better reversibility of the former system.
文摘Methyl methacrylate (MMA) was polymerized with the rare earth coordination catalyst system of Nd(O? Pr) 3 in toluene. The influences of various ligands in neodymium complexes, molar ratio of Al/Nd, catalyst concentration, catalyst aging time, solvents, the third component CCl 4, temperature and time on the polymerization of MMA were studied. The results showed that the polymerization conversion reached more than 80% at a catalyst concentration of 9 2×10 -3 mol/L. The appropriate molar ratio of CCl 4/Nd was 4. Hydrocarbon was preferred for the polymerzation to obtain a high conversion and a high M W of PMMA. The 1H NMR spectra of PMMA indicated that the lower the temperature, the higher the syndiotactic content of PMMA was obtained.
文摘Methyl methacrylate （MMA） was polymerized by using of benzoyl peroxide （BPO） and N, N-dimethylaniline （DMA） as an redox initiator in fluorous triphasic system at room temperature. The polymerization was occurred in both initiator layer and monomer layer in a U-tube. It was found that PMMA obtained from the initiator layer with relatively narrow polydispersity.（PDI = 1.38）
基金the National Natural Science Foundation of China!(29774021)
文摘Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)_3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as R_p=K_p[c][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with c_I=3. 6 × 10^(-4).
基金sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China,the Science and Technology Innovation Program of the China National Petroleum Corporation,and the Key Laboratory of Advanced Polymer Materials of Shanghai(Grant No.08DZ2230500)the Science and Technology Innovation Program of China National Petroleum Corporation.
文摘Two types of salicylaldiminato-based nickel complexes,mono-ligated Ni(II)complexes([O-C_(6)H_(4)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(5),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(6),[O-(3-t-Bu)C_(6)H_(3)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(7))and bis-ligated Ni(II)complexes([O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]_(2)Ni(8),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-2-C_(6)H_(4)(PhO)]_(2)Ni(9),Ar=2,6-C_(6)H_(3)(i-Pr)_(2))were synthesized and characterized by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(NMR),mass spectrography(MS)and elemental analysis(EA).In the presence of methylaluminoxane(MAO)as cocatalyst,all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate(MMA)and syndiotactic-rich poly(methyl methacrylate)(PMMA)was obtained.The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities,while with the same salicylaldiminato,the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.
文摘The polymerization of MMA by coordination catalyst of Nd(naph) 3 Al(i Bu) 3 α,α’ Dipyridyl was described in this paper.Characterization of the structure of the polymer is revealed by NMR and IR.These studies revealed that the polymer obtained has mainly syndiotactic and shetero structures.Molecular weight and distribution are studied by GPC.Coordinate mechanism was proposed for the MMA polymerization by Nd Al α,α’ Dipyridyl.Kinetic studies showed that the MMA polymerization rate is first order with respect to monomer concentration.The apparent activation energy of MMA polymerization reaction is 22.2 kJ/mol.
