基于RAFT过程的丙烯酸可控自由基聚合

Controlled Radical Homopolymerization of Acrylic Acid Based on RAFT Polymerization

以2-{[(十二烷基硫基)硫代甲酰基]硫烷基}琥珀酸(DCTSS)为链转移剂(CTA)在水溶液中调控丙烯酸(AA)进行可逆加成-断裂链转移自由基聚合(RAFT)。考察了引发剂种类、聚合温度、n(引发剂)/n(CTA)、n(AA)/n(CTA)、时间对丙烯酸聚合的影响。结果表明,以4,4′-偶氮二(4-氰基戊酸)(V501)为引发剂,聚合反应具有活性可控聚合的特征,聚合动力学呈线性关系,聚合物的黏均相对分子质量(以下简称黏均分子量)随转化率的增加而线性增加,得到分子量可控、分布为1.50左右的聚合物;升高温度可以加快反应速率,使黏均分子量分布降低,反应更加可控;降低n(V501)/n(CTA)值可以使聚合产物的黏均分子量升高,但聚合速率也会降低;随着n(AA)/n(CTA)值的增加,聚合产物的黏均分子量也增加,并且基本呈线性关系;最佳反应时间为2h;用所得聚合物作为大分子RAFT试剂,丙烯酸正丁酯(BA)为单体进行扩链反应,得到聚丙烯酸-b-聚丙烯酸正丁酯;用核磁共振氢谱、傅立叶变换红外光谱对产物结构进行了表征。

The reversible addition-fragmentation chain transfer （RAFr） free radical polymerization of acrylic acid （ AA ） was investigated by using 2- { [ （ dodecylsulfanyl ） carbonothioyl ] sulfanyl } succinic acid（ DCTSS ） as chain transfer agent （CTA） in water. The effects of some parameters on the polymerization of acrylic acid was investigated, such as ： kinds of initiator, temperature, time, the molar ratio of initiator to RAFT agent, and that of acrylic acid to RAFT agent. The polymerization showed ＂living＂/controlled characteristics by using 4,4 ＇-azobis （4-cyanovaleric acid） as initiator. The reaction kinetics was linear. The molecular weight of polyacrylic acid （PAA） was controllable and increased linearly with the monomer conversion. The molecular weight distribution of PAA was as narrow as 1.50. Raising the temperature could increase the rate of reaction, reduce the molecular weight distribution, and control the reaction better. Reducing the molar ratio of initiator to RAFT agent could increase the molecular weight, but the rate of the reaction was lower. Increasing the molar ratio of acrylic acid to RAFT agent, the molecular weight also increased, and the relationship between them was linear. The optimal reaction time was 2 h. The well-controlled amphipathic block copolymer PAA-bPBA was prepared by using PAA as macromolecular RAFT agent and n-butyl acrylate as second monomer. The structures of these products were characterized by 1HNMR and FTIR.