科研之友
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摘要
A new dinitroxide (1,4-di (1-oxy-2,2,6,6-tetramethyl-1-piperidin-4-yl)-xylene) (DTPX) was synthesized and successfully used in stable free radical polymerization of styrene. The results of the polymerizations showed that the DTPX was a suitable mediating agent for stable free radical polymerization of styrene. However, it was found that the dinitroxide mediating process resulted in a higher level of decomposition of the internal bisalkoxyamine linkage in the polymer chain, which resulted in polymers possessing a terminal alkoxyamine and an adjacent hydroxylamine, and the decomposition became more obvious at high conversion through monitoring the change of molecular weights with the conversion by gel permeation chromatography and the polymer structure by H-1-NMR. The reaction temperature showed obvious effects on the polymerization, and the polymerization of styrene at 110 degrees C led to a better controlled polymerization than that at 125 degrees C with narrower molecular weight distributions and slight decomposition of the nitroxide up to monomer conversions of 76.7%, however, the rate of the polymerization was decreased and an induction period appeared at 110 degrees C.
