聚合诱导自组装制备多腔室囊泡以及成核链段中亲溶剂片段的影响

Preparation of Multi-chambered Vesicles by Polymerization-induced Self-assembly and the Influence of Solvophilic Fragments in the Core-forming Blocks

聚合物纳米材料的形貌对于其性能具有重要的影响,其中囊泡(特别是多腔室囊泡)由于其具备空心结构备受关注.聚合诱导自组装(PISA)是一种高效的制备聚合物纳米材料的方法.然而,目前利用PISA高效制备多腔室囊泡的报道则相对较少.本工作中,以聚乙二醇为大分子可逆加成-断裂链转移(RAFT)试剂(PEG45-PETTC)调控苯乙烯(St)在混合溶剂乙醇/水(质量比7/3)中的RAFT聚合诱导自组装,成功制备了多腔室囊泡.同时开展了St和寡聚乙二醇甲醚甲基丙烯酸酯(OEGMA)的RAFT共聚合诱导自组装,探索在成核链段中引入亲溶剂基元OEGMA对所得纳米材料形貌的影响.由于聚苯乙烯的链刚性较强,在聚苯乙烯链段中引入亲溶剂链段来增加成核链段的柔顺性是一种已报道的促进形貌转变的方法.然而St和OEGMA在混合溶剂乙醇/水(质量比7/3)的聚合诱导自组装体系中,发现亲溶剂基元(OEGMA)的引入,导致所得纳米材料的形貌退化.随着成核链段中亲溶剂基元的增加,所得纳米材料逐渐由多腔室囊泡转变为单腔室囊泡和球形胶束.

The morphology of polymeric nano-objects has an important influence on its properties, among which vesicles(especially multi-chambered vesicles) have attracted much attention due to their hollow structures. Polymerization-induced self-assembly(PISA) is an efficient method for preparing polymeric nano-objects. However, there are relatively few reports on the efficient preparation of multi-chambered vesicles by PISA. In this paper, multi-chambered vesicles were successfully prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization-induced self-assembly using styrene(St)as monomer, ethanol/water(7/3, mass ratio) as the solvent and polyethylene glycol(PEG45-PETTC) as macro RAFT reagent.At the same time, RAFT copolymerization-induced self-assembly of St and oligoethylene glycol methyl ether methacrylate monomers(OEGMA) were carried out to explore the effect of introducing solvophilic moiety OEGMA into the core-forming blocks on the morphology of the resulting nano-objects. Due to the strong chain rigidity of polystyrene, the introduction of a solvophilic segment into the polystyrene segment to increase the flexibility of the core-forming blocks is a reported method to promote morphology evolution. However, in the polymerization-induced self-assembly system of St and OEGMA in ethanol/water(7/3, mass ratio), the introduction of solvophilic moieties(OEGMA) resulted in the morphology degradation of the resulting nano-objects. With the increase of solvophilic moieties in the core-forming blocks, the resulting nano-objects gradually transformed from multi-chambered vesicles to unicellular vesicles and spherical micelles. Random copolymer P(St-co-OEGMA) of the core-forming blocks in the corresponding nano-objects were formed by RAFT copolymerization of St and OEGMA. The solvated degree of the core-forming blocks increased due to the introduction of solvophilic OEGMA moieties. Moreover, the large side groups may also increase the free volume of core-forming blocks. The increasing of the free volume and solvated degree of the core-forming blocks synergistically weakened the packing strength of the core-forming blocks, leading to adversely effects on morphology transition of the nano-objects. We believe that the results of this study is a good complement to the current polymerization-induced self-assembly system.