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2′-Azobis(2-amidinopropane)dihydrochloride (AIBA) initiator can be efficiently and stably adsorbed onto nanometer silica particles via electrostatic adsorption

and then it can initiate the in situ polymerization of acrylate monomer onto/from the silica particles surface.In order to investigate the activity of adsorbed initiator and the action of adsorbed initiator in the in situ polymerization

the thermal decomposition behaviors of pure AIBA

noadsorbed AIBA and adsorbed AIBA were studied by differential scanning calorimetry (DSC)

and the polymerization kinetics of methyl methacrylate (MMA) in in situ emulsion polymerization and in conventional emulsion polymerization was compared by gravimetric method.It was found the thermal decomposition energy of no-adsorbed AIBA and adsorbed AIBA was 148.5 kJ/mol and 124.5 kJ/mol

and their half-life time at 70℃ were 12.6 h and 5.2 h

respectively.All of them implied that the adsorbed AIBA was of higher activity

which finally brought the weakening of the induction period and the improvement of polymerization rate in in situ emulsion polymerization.The anchoring degree and anchoring efficiency of PMMA onto nanosilica particles during in situ emulsion polymerization were further studied by extraction treatment and elemental analysis.It was found that the anchoring of PMMA onto/from silica particles was the dominant means in the early stage.Thus

it is the absorbed AIBA that facilitate the initiation of polymerization on silica surface

which would improve the anchoring of polymer onto/from silica particles and subsequently the composite degree between silica particles and polymer remarkably.