甲基丙烯酸N,N-二甲氨基乙酯/丙烯酸N,N-二甲氨基乙酯的可逆加成断裂链转移聚合研究

合成了二硫代苯甲酸2- (乙氧基羰基)异丙酯(ECPDB)、二硫代苯甲酸异丙苯酯(CDB)、二硫代苯甲酸1 苯基乙酯(PEDB) 3种二硫代苯甲酸酯链转移剂.以这3种转移剂为基础,用凝胶渗透色谱和核磁共振测试了甲基丙烯酸N ,N 二甲氨基乙酯(DMAEMA)和丙烯酸N ,N 二甲氨基乙酯(DMAEA)两种碱性单体的可逆加成断裂链转移(RAFT)聚合的聚合物分子量、分子量分布和结构.发现有的聚合体系聚合物分子量分布较窄,但实验数均分子量与理论数均分子量相差较大;有的体系则转化率很低,聚合物分子量很小.这些可能是由聚合体系中单体活性和链转移剂链转移能力之间的匹配不太协调,使可逆加成断裂链转移快速平衡反应发生偏移或破坏造成的.因此,可通过更换单体或链转移剂来调节这种匹配,从而使可逆加成断裂链转移快速平衡保持稳定,达到聚合更可控,实验分子量与理论分子量更接近,分子量分布更窄的目的.

REVERSIBLE ADDITION-FRAGMENTATION CHAIN TRANSFER POLYMERIZATION OF 2- (DIMETHYLAMINO) ETHYL METHACRYLATE/2- (DIMETHYLAMINO) ETHYL ACRYLATE

Poly(2-(dimethylamino)ethyl methacrylate (PDMAEMA) and poly(2-(dimeth yl amino) ethyl acrylate (PDMAEA) were prepared by using chain transfer agents (CTA ),dithioesters (2-(ethoxycarbonyl)prop-2-yl dithiobenzoate(ECPDB),cumyl dit hio benzoate(CDB) and 1-phenylethyldithiobenzoate (PEDB) respectively,through reve r sible addition-fragmentation chain transfer (RAFT) polymerization.The molecula r weight and molecular weight distribution of PDMAEMA and PDMAEA,were measured b y gel permeation chromatography (GPC) and nuclear magnetic resonance spect rometer ( 1H-NMR).The results showed the molecular weight distribution of PDMAEM A was narrow when the ECPDB/AIBN and CDB/AIBN as the initiator respectively.But the theoretical number average molecular weight M n,th was not in good agreement with M n,NMR and M n,GPC.It demonstrated that the mo lecular weight of polymers could not be controlled.Its reason is probably that the balance of the reversible addition-fragmentation chain transfer is di sturbed by unapt match of mono m er and CTA.With changing monomer or CTA,the molecular weight of polymers can be co ntrolled.Compared with the CDB/AIBN system,the molecular weight distr ibution of PDMAEA by using PEDB/AIBN was narrower,and the molecula r weight was controllable.