介孔核结构聚合物胶束的制备及其在汞离子检测中的应用

Fabrication of Mesoporous Polymeric Micelles and Their Application in Hg^(2+) Detection

通过可逆加成-断裂链转移聚合(RAFT)和原子转移自由基聚合(ATRP)设计合成了具有p H响应性和还原响应性的双亲性聚合物分子刷,聚聚(乙二醇)单甲醚甲基丙烯酸酯-block-(聚甲基丙烯酸叔丁酯-graft-聚甲基丙烯酸N,N-二甲氨基乙酯)(POEGMA-b-(Pt BMA-g-PDMAEMA)),其中侧链PDMAEMA与主链通过二硫键相连.运用核磁共振氢谱(1H-NMR)和凝胶渗透色谱(GPC)表征了聚合物的结构、分子量及分子量分布.在碱性条件下,聚合物分子刷自组装成以POEGMA为壳,Pt BMA和PDMAEMA为核的多组分胶束.由于Pt BMA和PDMAEMA互不相容,在核中形成微相分离,体积分数较大的Pt BMA形成连续相,体积分数较小的PDMAEMA形成分散相.调节p H至酸性条件后,分散相PDMAEMA由坍陷变为伸展状态,从胶束的核中溶解出来.加入还原剂断开侧链PDMAEMA与主链相连的二硫键,制得孔内壁含有巯基的介孔核结构聚合物胶束.利用透射电镜(TEM)和动态光散射(DLS)表征了胶束的形貌和粒径.通过TEM结果得出介孔核结构聚合物胶束的孔径大小约为2 nm.利用巯基对氯金酸的还原作用和对金纳米粒子的稳定作用,制得孔内修饰金纳米粒子的介孔核结构聚合物胶束.利用巯基和溴的点击反应,制得孔内修饰聚噻吩衍生物的介孔核结构聚合物胶束,其对Hg^(2+)检测表现出较高的灵敏度和特异性.

Amphiphilic macromolecular brushes with pH-responsiveness and reduction responsiveness were synthesized by reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization. The side chains of the brush polymers were covalently connected to the backbones through redox- responsive disulfide bonds. The structure, molecular weight and molecular weight distribution of the brush polymers were characterized by 1H-NMR and gel permeation chromatography. At pH = 10.0, the amphiphilic brush polymers self-assembled into multi-component micelles with POEGMA shells and PtBMA/PDMAEMA cores. In the cores, the two hydrophobic blocks segregated into distinct domains due to their incompatibility, and the hydrophilic POEGMA blocks formed the coronae to stabilize the structures. The PtBMA chains with larger volume percentage formed the continuous phases, while the PDMAEMA chains with smaller volume percentage formed the discontinuous phases. At pH = 4.0, protonated PDMAEMA chains were highly stretched and formed the coronae of the micelles. Excessive reductant was added into the micellar solution to reduce the disulfide bonds between PDMAEMA side chains and the backbones, and mesoporous polymeric micelles with thiol groups inside the pores were obtained. ~H-NMR results of multi-component micelles, before and after treatment with the reductant, indicated that the PDMAEMA side chains were removed completely. Transmission electron microscopy （TEM） and dynamic light scattering were used to characterize the morphology and the size of the micelles. Based on TEM results, the average size of the pores in the micelles was about 2 nm, which was consistent with the average size of the PDMAEMA discontinuous phases. After the cleavage of the disulfide bonds and the removal of PDMAEMA chains from the micelles, thiol groups were produced on the walls of the pores. The thiol groups can be used as reducing agent and stabilizer in the in situ synthesis of gold nanoparticles. By thiol-bromine reactions, mesoporous micelles with polythiophene derivatives inside the pores were synthesized. The micelles showed high sensitivity and excellent selectivity for Hg2＋.