Synthesis And Properties Of Responsive Composite Microgels

Responsive composite microgels are a kind of polymer materials prepared by embedding inorganic particles in the network structure of the responsive microgels. They combine the properties of both the inorganic nanoparticles and responsive polymer microgels. On the one hand, they are easy to be modified, and the crosslinked network structure of the microgels can be used as reactor for inorganic nanoparticles when they are prepared via in situ reduction by reducing agent, avoid metal nanoparticles aggregation and improve the stability of the inorganic nanoparticles. The size and morphology of the nanoparticles can be adjusted by the amount of cross-linker. Moreover, the chemical and physical properties of the inorganic nanoparticles can be controlled by varying the environmental conditions of responsive composite microgels. On the other hand, by embedding inorganic particles in the network structure of the responsive microgels by appropriate way, it can give some performances to microgels and broad the range of applications of microgels. It was a challenge to prepare a kind of pH-responsive cationic microgels with core-shell structure, then based on a polymer microgel template method, responsive composite microgels with a great stability were prepared through a simple and effective method. Based on the previous research work of our group, In this paper, we used 2-(diethylamino) methyl methacrylate as a cationic monomer, through designing the structure and the morphology of the microgels. Our accomplishments involves three parts:(1) pH-responsive cationic microgels poly(methylmethacrylate)/ poly(2-(diethylamino) methyl methacrylate)(PMMA/PDEAMA) with core-shell structures were synthesized by seed emulsion polymerization. On this basis, in order to simplify the process, based on the idea of molecular designing, PMMA/PDEAMA core-shell microgels were prepared by one-pot emulsion polymerization of DEAMA and MMA as a result of the differences of reactivity ratio and hydrophilcity between them. It was demonstrated that core layer of the cationic core-shell microgels prepared by one-pot emulsion polymerization was PMMA, shell layer of the cationic core-shell microgels was PDEAMA.(2) Based on a polymer microgel template method, a certain amount of chloroauric acid (HAuCl4) solution was fully complexed to the network structure of the microgels. PMMA/PDEAMA-Au composite microgels were prepared via in situ self-reduction taking advantage of polymer as reducing agent at different temperatures. It was demonstrated that Au nanoparticles (Au NPs) were dispersed in the shell layer, Au NPs were cubic crystal structure, the formation rates and size of Au NPs could be regulated by temperature. The size and spectral properties of PMMA/PDEAMA-Au had a good pH-responsibility. The surface plasmon band of PMMA/PDEAMA-Au was shifted in response to pH.(3) The magnetic cationic microgels were successfully prepared by emulsion polymerization process in the presence of oleic acid coated magnetite particles. It was demonstrated that the magnetic microgels exhibited an excellent stability and had a high magnetic content, the size of the magnetic microgel particles was about 150 nm. It could be simply and effectively separated from solutions by external magnetic field.