Photografting of vinyl polymers onto ultrafine inorganic particles: Photopolymerization of vinyl monomers initiated by AZO groups introduced onto these surfaces

Abstract

SYNOPSISThe photografting of polymers onto ultrafine inorganic particles, such as silica and titanium oxide, initiated by azo groups introduced onto these surfaces was investigated. The introduction of azo groups onto the particles was achieved by the reaction of 4,4'-azobis (4cyanopentanoic acid) with surface isocyanate groups, which were introduced by the treatment with tolylene 2,4-diisocyanate. It was found that the photopolymerization of vinyl monomers, such as methyl methacrylate (MMA), styrene, and N-vinylcarbazole, is initiated by ultrafine particles having azo groups. The corresponding polymers were effectively grafted onto these surfaces through the propagation of the polymer from the surface radicals formed by the photodecomposition of the azo groups: e.g., the percentage of grafting of PMMA and polystyrene onto silica was reached to 112 and 176%, respectively. The percentage of grafting onto silica in the graft polymerization initiated by photodecomposition of surface azo groups was much larger than that initiated by thermal decomposition. Polymer-grafted ultrafine particles thus obtained gave a stable colloidal dispersion in good solvents for the grafted chain.

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

“…10 We reported the radical graft polymerizations initiated from alkylazo groups attached onto ultrafine inorganic particles, such as carbon black, silica, ferrite, and titanium oxide. [13][14][15] Furthermore, studies on synthesis of macroazoinitiators and their applications for preparing block and graft copolymers are also reported by many researchers. 16 -23 Radical grafting initiated from glass fiber surface, however, has been scarcely reported.…”

“…The percentage of reacted surface hydroxyl groups in the introductory reaction of the azo groups were calculated to be 13% from the azo group content, while each value in the case of carbon black, silica, and titanium oxide was 52%, 6%, and 4%. [13][14][15] The azo group content was reproducible to about 1% on repeated runs.…”

“…10 In order to connect alkylazo groups onto surfaces of ultrafine particles, such as carbon black, silica, ferrite, and titanium oxide, we investigated the reactions of ACPA with epoxide or isocyanate groups attached onto the surface [13][14][15] and ACP with acyl chloride groups introduced onto the surface 13 because aliphatic carbon radicals produced by decomposition of alkylazo groups were considered to be more active than phenyl radicals induced from phenylazo groups.…”

“…Into a 200 cm 3 flask, 1.5 g of glass fiber, 0.5 cm 3 of TDI, 0.1 cm 3 of 2-methylpyridine, and 100 cm 3 of DMSO were charged. 15,26,27 The mixture was stirred with a magnetic stirrer at 60°C under dry nitrogen, and after the reaction for 4 h, the flask was cooled to room temperature. Then 1.3 g of ACPA or 1.4 g of ACP was added to the reaction mixture, and the reaction was continued with stirring under nitrogen for 8 h at 25°C.…”

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“…TGA curves of the products from one-step procedure (1), TDI pre-grafting procedure(2) and urethane procedure (3) at 20°CFig. 5TGA curves of the products from onestep procedure (1), TDI pre-grafting procedure (2) and urethane procedure (3) at 80°C…”