含吲哚侧基聚苯乙烯的合成及其后修饰

Synthesis and Post-polymerization Modification of Polystyrene Containing Indole Side Group

通过可逆加成-断裂链转移(RAFT)聚合合成了一种含吲哚侧基的聚苯乙烯.在B(C6F5)3的催化下,硅烷与吲哚C3位的选择性硅烷化反应实现了所得聚苯乙烯的后修饰.聚合物通过GPC和1H-NMR表征,证明在不破坏聚苯乙烯主链的情况下,聚合物侧链引入了C3硅烷化吲哚侧基.在选用位阻较小的苯基二甲基硅烷(PhMe2SiH)进行修饰时,所得聚苯乙烯的硅烷化吲哚侧基的嵌入率可达50%.在选用含四苯乙烯的硅烷进行修饰时,所得聚苯乙烯的硅烷化吲哚侧基嵌入率可达38%,且具有聚集诱导发光(AIE)性质.

A vinyl monomer 1-(4-vinylbenzyl)-indole was prepared in 90%yield through one-step synthesis by using commercially available starting material.The reversible addition-fragmentation chain transfer(RAFT)polymerization of 1-(4-vinylbenzyl)-indole was performed with 2,2-azobisisobutyronitrile(AIBN)as initiator and 2-phenyl-2-propylbenzodithiolate as chain transfer agent(CTA),furnishing a series of polystyrenes containing indole side groups with adjustable molecular weight(Mn=5200–18500 g/mol).With the catalysis of B(C6F5)3,post-polymerization modification of the produced polymers could be achieved through the regioselective silylation of their indole side groups with different hydrosilanes.Analysis of the polymers by GPC and 1H-NMR spectroscopy revealed that the C3-position of indole group at the polystyrene side chain was selectively silylated while the polymer backbone was maintained.The employment of the less sterically crowded PhMe2SiH or silanes containing tetraphenylethene(TPE)-moiety as silane sources led to the production of polymers with 50%or 38%grafting ratio of silylated indole,respectively.Moreover,silanes containing tetraphenylethene(TPE)-moiety would endow the resultant polymer with the aggregation-induced emission feature.Under UV irradiation,almost no fluorescence was observed for polymer containing TPE-moiety dissolved in THF.The addition of large amounts of hexane to THF led to the observation of a relatively strong blue fluorescence.With an increase in the hexane fractions(fw)of mixed solvents,the corresponding fluorescence intensity gradually increased until reaching the maximum value at fw of 90%,which is approximately 57-fold higher than that in pure THF solution.