“一锅法”聚合诱导自组装制备嵌段共聚物纳米粒子

One-pot Preparation of Block Copolymer Nanoparticles by Polymerization-induced Self-assembly

采用'一锅法'合成了聚4-乙烯基吡啶-b-聚(4-乙烯基吡啶-r-苯乙烯)(P4VP-b-P(4VP-r-St))两亲性共聚物纳米粒子.采用可逆加成-断裂链转移(RAFT)聚合制备了结构明确的P4VP三硫代碳酸酯(P4VPTTC);以P4VP-TTC为大分子链转移剂在醇/水混合溶剂中进行St和4VP的RAFT分散共聚合反应,得到了球状、蠕虫状和囊泡状的共聚物胶束;考察了亲溶剂链段和疏溶剂链段的聚合度之比、P(4VP-rSt)嵌段中共聚单体4VP的用量、溶剂组成对嵌段共聚物纳米粒子形貌、尺寸及形貌发展过程的影响.与相同条件下St的分散聚合相比,亲溶剂单体4VP和St的分散共聚能有效调控嵌段共聚物纳米粒子的形貌和尺寸,更易发展出囊泡胶束.利用透射电子显微镜(TEM)、凝胶渗透色谱(GPC)、动态光散射(DLS)和核磁共振氢谱(1H-NMR)表征了共聚物的组成和纳米粒子结构.

Polymeric vesicles have important applications in biomedicine,nuclear magnetic imaging,nanoreactors,and catalyst fields.Amphiphiic block copolymer nanoparticles with different morphologies(such as vesicles and spheres),sizes and surface chemical properties have been successfully prepared by reversible addition-fragmentation chain transfer(RAFT)polymerization-induced self-assembly(PISA).Generally it is difficult for researchers to obtain pure vesicles with different sizes.In this study,we report an efficient approach to produce block copolymers vesicles by PISA.A one-pot,facile method for the synthesis of nano-objects composed of amphiphilic poly(4-vinylpyridine)-b-poly(4-vinylpyridine-r-styrene)block copolymer,P4 VP-b-P(4 VP-r-St),is introduced by P4 VP trithiocarbonate macro-RAFT agent mediated dispersion copolymerization of 4 VP and St in ethanol/water mixture.It is found that the morphology of P4 VP-b-P(4 VP-r-St)diblock copolymer nano-objects like spherical micelles,worms,and vesicles can be easily tuned either by changing the degree of polymerization of the random P(4 VP-r-St)block,the amount of 4 VP comonomer,solvent composition and the ratio of the degree of polymerization of PSt and P4 VP segments.Among them,by adding a small amount of 4 VP comonomer during the dispersion RAFT polymerization of St,the final morphology of the block copolymer can be greatly affected,pure vesicle can be formed and the size can be adjusted more effectively.Compared with the dispersion RAFT polymerization of St,the advantage of the dispersion RAFT copolymerization by utilizing residual solvophilic monomer to tune the block copolymer morphology is demonstrated.It is believed to be a novel,convenient and efficient protocol for the control of the morphology and size of the block copolymer nano-objects fabricated by PISA.The polymerization shows characteristic features of'living'/controlled radical polymerization and the experimental results are confirmed by gel permeation chromatography(GPC),dynamic light scattering(DLS),transmission electron microscopy(TEM)and 1 H-NMR.Due to diverse potential applications of polymer vesicles,the results of this study are of great importance for the theoretical design and application of PISA strategies.