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The role transition of poly(N-isopropylacrylamide) ionic microgels (PNI microgels) in dispersion polymerization by changing the monomer type was investigated in this work. Firstly, PNI microgels with different diameters were prepared by precipitation polymerization. Then they were respectively employed to the dispersion polymerization of glycidyl methacrylate (GMA) and styrene (St) in methanol. Finally, poly(glycidyl methacrylate) (PGMA) and polystyrene (PS) nanoparticles were obtained. The morphology, thermo-sensitivity and element analysis of PNI microgels and these polymer nanoparticles were characterized. It indicated that GMA polymerized inside the microgels while the polymerization of St occurred outside the microgels. This phenomenon demonstrated that the PNI microgels acted as seed for the polymerization of GMA while turned into particulate stabilizer for the polymerization of St. The mechanism of the role transition of PNI microgels from seed to particulate stabilizer was discussed. It revealed that compatibility and chemical interaction between PNI microgels and monomers contributed a lot to this role transition.

Preparation of small size core-shell polymer nanoparticles has significant applications in photonic crystal materials and drug delivery systems. Although core-shell nanoparticles could be easily prepared by seeded emulsion polymerization, their size was generally larger than that of seeds, which limited their further applications in some areas. In this work, a new method was utilized to prepare small size core-shell polymer nanoparticles. In detail, poly(N-isopropylacrylamide) ionic microgels (encoded as PNI microgels) with controllable diameter were firstly prepared and then used as seeds in seeded emulsion polymerization of styrene. After polymerization, core-shell nanoparticles which were smaller in size than that of seeds were obtained. In order to reveal this abnormal phenomenon, the inner structure, components, element distribution, thermo-sensitivity and deformability of the obtained nanoparticles were characterized by TEM, FTIR, DSC, EDS, DLS and AFM. It was found that the core composed of polystyrene and the shell composed of PNI microgels in the core-shell nanoparticles. The detailed formation process was then studied systematically. It was found that polystyrene nanoparticles formed within PNI microgels and peeled off from the seeds when they were large enough. Considering the weak ionic interaction of PNI microgels, mechanism for this phenomenon was proposed. Factors, such as initiator type, microgel type, cross-linking degree and stirring speed, also had significant effects on the formation of core-shell nanoparticles.

As a new environmentally friendly liquid dielectric material, vegetable insulating oil has been used in oil-filled transformers more and more widely. In transformers, ageing, overheating faults, and discharge faults cause the decomposition of insulating oil and insulating paper, and then cause dissolved gases in the oil. These transformer fault diagnosis and prediction can be realized by Dissolved Gas-in-oil Analysis (DGA) method, which is closely related to the diffusion process of gas in oil. However, few research involves diffusion processes of dissolved gases and thus no effective DGA method for vegetable insulating oil-filled transformers has been proposed. In this paper, in order to have a better understanding for vegetable oil transformer fault process and improve the effective of DGA method as theoretic support for vegetable oil transformers, the research of diffusion properties and mechanism of characteristic gases in camellia insulating oil is very meaningful. The molecular dynamics simulation based on polymer consistent force field (PCFF) was adopted to analyze diffusion processes of characteristic gases. Impacts of gas species as well as temperatures for molecular diffusion coefficients were studied. The result provides theoretic support for fault condition assessment and operating maintenance of vegetable insulating oil-filled transformers, and also has great theoretical reference value for ensuring safe operation of vegetable insulating oil-filled transformers.