用双硫酯链转移法合成嵌段聚合物

SYNTHESES OF A-B TYPE BLOCK COPOLYMERS USING 1-PHENYLETHYL DITHIOBENZOATE AS RAFT AGENT

研究了以双硫酯为链转移剂进行的均聚和嵌段共聚物的合成 .首先合成大分子链转移剂 ,得到分子量可控、多分散性系数较小的均聚物PMMA、PBMA、PEMA、PEA、PBA、PMA、PSt,多分散性系数一般小于 1 30 .在相同的条件下 ,甲基丙烯酸酯类的聚合速度最快 ,苯乙烯其次 ,丙烯酸酯类最慢 .用末端带有双硫酯基团的PSt、PBMA、PBA为链转移剂 ,加入多种第二单体聚合得到实测分子量与理论分子量接近 ,且多分散性系数较小的两嵌段聚合物 .在链转移剂和引发剂的比例为 3∶1～ 6∶1的范围内 ,聚苯乙烯同样可以作为第一嵌段得到和其它酯类单体的两嵌段聚合物 .1 H NMR方法证明了聚合物的末端带有双硫酯基团 .嵌段聚合时必须加入微量的自由基引发剂以形成大分子自由基 。

The syntheses of the homopolymers and diblock copolymers by adding dithioester as chain transfer agent. First a series of monomers:methyl methacrylate (MMA), butyl methacrylate (BMA),methyl acrylate (MA),ethyl acrylate(EA),butyl acrylate (BA), and styrene (St) were polymerized in bulk by Reversible Addition-Fragmentation Chain Transfer (RAPT) polymerization. All of these homopolymers (PMMA, PBMA, PEA, PBA, PMA, PSt) have the controllable polymerization characteristics, the polydispersity index (PDI) is narrow (1.08 similar to 1.30). At the same reaction conditions the rate of polymerization of the methacrylate is the fastest, styrene is slower, acrylate is the slowest. The higher the reaction temperature, the faster the polymerization rate, The effects of the molar ratio of chain transfer agent to initiator on polymerization and the effects of conversion and reaction time on the molar mass characteristics of the prepared block copolymers were discussed. The diblock copolymers have the characteristics of the controlled/living radical polymerization, that is to say that the real molecular-weight of these copolymers is similar to the theoretical molecular-weight, and the polydispersity index is less than 1.80, When the molar ratio of ABIN to CTA is ranged from 1:3 to 1:6, the copolymers with PSt as the first block also have characteristics of the controlled/living radical polymerization, The H-1-NMR spectra of the homopolymer (PMMA) and copolymer (PMMA-b-PEA) showed that the synthesized polymers have functional groups, dithioester, at the end of these polymers.