聚甲基丙烯酸单层修饰金纳米粒子的制备及pH响应性催化

Preparation of Poly(methylacrylic acid) Monolayer-protected Gold Nanoparticles and Its pH Responsive Catalysis

采用可逆加成断裂链转移(RAFT)聚合制备了具有硫醇端基的聚甲基丙烯酸叔丁酯(PtBMA),通过其水解得到具有pH刺激响应的聚甲基丙烯酸(PMAA)。利用硫醇端基与金之间的强耦合作用获得了聚甲基丙烯酸单层修饰的金纳米粒子(PMAA-GNPs)催化体系。利用UV-Vis光谱和透射电子显微镜(TEM)研究了PMAA-GNPs催化剂在不同pH值下的分散状态。以NaBH4还原对硝基苯酚的反应,验证了此催化体系的pH响应性。结果表明,调节体系的pH值为酸性,PMAA塌缩和包覆在金纳米粒子(GNPs)的表面,引起GNPs的聚集,从而降低了催化效率。反之,在碱性环境中,在PMAA链的排斥作用下,GNPs能较好的分散,提高催化效率。

The pH stimuli-sensitive polymer, poly （methylacrylic acid） （PMAA）, was firstly obtained by reversible addition-fragmentation transfer （RAFT） polymerization of tert-butylmethacrylate （PtBMA） and then hydrolysis. The PMAA monolayer-protected gold nanoparticles （PMAA-GNPs） was prepared via the strong binding between the thiol groups on the polymer chain-ends and gold. The dispersion and aggregation of PMAA-GNPs could be tuned by controlling the pH values of the solution, which was investigated by UV-Vis spectra and TEM, It was found that the catalytic activity was responsive to pH when it is applied in the catalytic reduction of the 4-nitrophenol by NaBH4. The responsive mechanism could be interpreted as ： the,hydrophobic PMAA collapsed onto the surface of the GNPs in the acid solution, which hindered the contaction between reactant and GNPs, and reduced the catalytic activity. On the contrary, in the alkaline system, polymer chains repulsion due to electrostatic effect can improve the catalytic activity.