RAFT聚合制备结构明确的荧光标识聚甲基丙烯酸甲酯

以铁氰化钾为氧化剂,通过N-咔唑二硫代甲酸钠的水相氧化制备了高纯度的中间体二硫化双(N-咔唑硫代甲酰)(DTCD),DTCD以晶体的形式从水中析出,提纯简单,性质稳定.通过DTCD与偶氮二异丁腈(AIBN)或偶氮二氰基戊酸(ACVA)的反应合成了2种性能优异的叔丁腈酯基RAFT试剂,N-咔唑二硫代甲酸异丁腈酯(CYCBD)和N-咔唑二硫代甲酸氰基戊酸(CVCBD),新合成工艺的副反应和杂质被大量减少,最终产物的收率可达80%以上.以CYCBD和CVCBD为可逆加成断裂链转移(RAFT)试剂,研究了它们对甲基丙烯酸甲酯(MMA)RAFT聚合的控制能力,结果表明CYCBD和CVCBD是性能优异的RAFT试剂,可以很好地用于制备结构明确、分子量分布窄的链末端咔唑标记的聚甲基丙烯酸甲酯(CPMMA),由它们所制得的CPMMA的PDI小于1.2.研究结果还表明CYCBD和CVCBD及由其合成的CPMMA在四氢呋喃(THF)溶液中具有显著的荧光特性,CPMMA在358nm处有很强的荧光发射峰,而且,在浓度范围为0.1～20μmol/L的THF溶液中,CPMMA的荧光发射强度与其浓度具有良好的线性关系.通过CYCBD和CVCBD可以方便地制备结构明确且具荧光标识的功能聚合物。

SYNTHESIS AND INVESTIGATION OF WELL-DEFINED AND FLUORESCENCE-LABELLED POLY (METHYL METHACRYLATE) BY RAFT POLYMERIZATION

In order to synthesize cyanic RAFT agents for RAFT polymerization of methyl methacrylate(MMA),an improved aqueous phase method was developed to prepare di(thiocarbazolyl) disulfide(DTCD) with carbazole as main material and potassium ferrocyanide as oxidant.Compared with the traditional oil-phase method,the expected high purity DTCD was obtained in the form of crystal that was precipitated and separated from the aqueous solution.Then,2-cyanoprop-2-yl N-carbazolylcarbodithioate(CYCBD) and 4cyanovalericacid N-carbazolylcarbodithioate(CVCBD) were synthesized based on a substitution reaction between DTCD and azobisisbutyronitrile(AIBN) or azobis(cyanovaleric acid)(ACVA).The activities of CYCBD and CVCBD as RAFT agents for the polymerizations of MMA were determined,and the results showed that both of the RAFT agents were of significant activity in the RAFT polymerization of MMA and molecular weight distribution of fluoresence-labelled poly(methyl methanylate) CPMMA prepared by CYCBD or CVCBD is less than 1.2.The fluorescence characteristics of CYCBD and CVCBD as well as CPMMA prepared by CYCBD or CVCBD were also studied.The results showed that all of them exhibited significant fluorescence in tetrahydrofuran(THF) solution.Moreover,CPMMA prepared by CYCBD or CVCBD possesses obvious fluorescence emission at a wavelength of 358 nm,and there is a good linear relationship between fluorescence intensity and concentration of CPMMA when the concentration of CPMMA in the range of 0.1 ～ 20 μmol /L.In a word,CYCBD and CVCBD as RAFT agents possess good control ability and can be used to synthesize fluorescence-labelled polymers with well-defined structure.