X. Shen's scientific contributions

γ-Ray irradiation was successfully used in the surfactant-free emulsion copolymerization of N,N′-methylenebisacrylamide(Bis) and 4-vinylpyridine(4-VP), leading to a series of microgels with average hydrodynamic radius(Rp) ranging from 56 nm to 152 nm. However, when acrylic acid (AA), methacrylic acid (MAA) or acrylamide(AM) were used instead of 4-VP, unstable white emulsions or white bulk gels were obtained. The poly (N,N′-methylenebisacrylamide-co-4-vinylpyridine) (poly( Bis-co-4-VP) ) microgels were characterized by infrared spectroscopy, differential scanning calorimetry and transmission electron microscopy. The effects of the ratio of monomers, absorbed dose and dose rate on the synthesis of poly(Bis-cos-4-VP) microgels were studied through Rh, absorbance and gel ratio. The results showed that the size of microgels could be controlled either by the absorbed dose or by the ratio of monomers. The mechanism concerning the formation of microgels was also discussed.