胺基磁性纳米凝胶的光化学制备及形成机理

Photochemical preparation and formation mechanism of amino-functionalized magnetic nanogels

以Fe3O4纳米粒子为磁核,借助紫外光辐照含有烯丙基胺和N,N′-亚甲基双丙烯酰胺的水溶液,制备了胺基功能化的聚(烯丙基胺-共-N,N′-亚甲基双丙烯酰胺)磁性纳米凝胶(PAAm-Fe3O4),对其化学组成、表面电位、形貌、粒径分布及磁学性质进行了分析表征,并研究了光照时间和单体的滴加量对产物的粒径和粒径分布的影响.为探索聚合反应的引发方式,以烯丙基胺的类似物——苯胺为探针,借助激光光解-瞬态吸收装置研究了纳米Fe3O4粒子与有机电子供体的相互作用.结果表明,光化学方法实现了高分子凝胶层对单个Fe3O4粒子的有效包覆,通过控制光照时间和单体的滴加量可以获得在一定范围内尺寸可调且分布较窄的PAAm-Fe3O4.核壳结构的PAAm-Fe3O4近似球形,表面带正电性,磁含量接近88%,在室温下呈现准超顺磁性且饱和磁化强度达50emug?1.激光光解实验结果表明在光化学反应条件下Fe3O4与有机电子供体发生了电子转移反应,这可能是在Fe3O4表面引发有机胺单体的聚合并形成高分子壳的关键.最后,对PAAm-Fe3O4的形成机理进行了探讨.

Poly（allylamine-co-N,N’-methylenebisacrylamide） magnetic nanogels （PAAm-Fe3O4） were prepared by photochemical polymerization of allylamine and N,N′-methylenebisacrylamide in magnetite aqueous suspension under UV irradiation. The composition, zeta potential, morphology, particle size distribution and magnetic properties of the product were characterized in detail. To explore the initiating process of polymerization, laser flash photolysis was used to investigate the interaction between Fe3O4 nanoparticles and organic electron donor by employing aniline as the probe molecule, an analogue of allylamine. It indicated an occurrence of electron transfer process from the organic electron donor to Fe3O4 which may be critical to initiate polymerization reaction of amino monomer and form polymer shell on the surface of Fe3O4 nanoparticles. The mean diameter and diameter distribution of PAAm-Fe3O4 can be tuned in a moderate range by varing irradiation time or volume of the dropped monomer. The experimental results also proved that nearly spherical PAAm-Fe3O4 possessed a core-shell structure and positive zeta potential and high magnetic content of nearly 88%. Moreover, it behaved quasi-superparamagnetic at room temperature and its saturation magnetization reached to 50 emu/g. Finally, a possible formation mechanism of magnetic nanogel was proposed.