甲基丙烯酸2-N,N-二甲氨基乙酯与甲基丙烯酸甲酯的氧化共聚合的机理研究

MECHANISTIC STUDY OF CATALYTIC OXIDATIVE COPOLYMERIZATION OF 2-(N,N-DIMETHYLAMINO)ETHYL METHACRYLATE AND METHYL METHACRYLATE

研究了CuCl/五甲基二亚乙基三胺(PMDETA)催化的甲基丙烯酸2-N,N-二甲氨基乙酯(DMAEMA)与甲基丙烯酸甲酯(MMA)在氧气存在下的氧化共聚合,通过改变单体配比、催化剂浓度和反应温度对实验条件进行研究.结果显示,在本实验中的单体配比([DMAEMA]∶[MMA]=10∶0～5∶5)、催化剂浓度([CuCl/PMDETA3]=3.1×10-5 mol/L～6×10-3 mol/L)和反应温度(30～80℃)下,聚合均可以顺利发生,而且聚合过程中单体转化率和所得聚合物的分子量都随着反应进行而增加,且分子量呈现宽分布.1H-NMR结果显示所得聚合物中含有DMAEMA和MMA的单体单元.DSC结果显示所得聚合物是一个部分相容体系.利用此方法所得的PDMAEMA进行MMA的原子转移自由基聚合(ATRP)扩链过程则证实,所得聚合物具有C—Cl末端官能团.由此可以认为,在以上过程中,O2先将CuCl氧化成[Cu(Ⅱ)Cl]+,[Cu(Ⅱ)Cl]+再将二甲胺基氧化成N—CH2.自由基,N—CH2.自由基与[Cu(Ⅱ)Cl]+构成反向ATRP体系,从而得到以C—Cl为末端的聚合物.

The CuX/pentamethyldi-ethylenetriamine（PMDETA）-catalyzed oxidative copolymerization of 2-（N,N-dimethylamino）ethyl methacrylate（DMAEMA） and methyl methacrylate（MMA） was investigated.The kinetics were compared by varying the monomer ratio,catalyst concentration and the reaction temperature.The results showed that the copolymerization could proceed under the monomer ratio（[DMAEMA]∶[MMA] = 10∶ 0 ～ 5∶ 5）,catalyst concentration（[CuCl /PMDETA3 ]= 3.1 × 10-5 mol/L ～ 6 × 10-3 mol/L） and the reaction temperature（30 ～ 80℃） which were investigated in the paper,and the molecular weight increased with the reaction time,while the molecular weight distribution maintained rather broad.It was showed from the 1 H-NMR that there were DMAEMA units and MMA units in the copolymer,while the DSC indicated that the system of copolymer was partially compatible.The CuCl /PMDETA-catalyzed atom transfer radical polymerization（ATRP） of MMA using the so-obtained PDMAEMA as the macroinitiator was successful,confirming the presence of the C-Cl terminal functionality.Thus,the following mechanism might operate： 1） O2 oxidized CuCl into [Cu（Ⅱ）Cl]＋ species;2） [Cu（Ⅱ）Cl]＋ oxidized dimethylamino moiety into N—CH2.radicals;3） N—CH2.radicals and[Cu（Ⅱ）Cl]＋ formed the reverse ATRP system.The above processes finally led to polymer with C—Cl end group.