To graft polymers with controlled molecular weight and narrow molecular weight distribution, the grafting of polymers onto ultrafine silica surface by the termination of living polymer cation with amino groups introduced onto the surface was investigated. The introduction of amino or N‐phenylamino groups onto the silica surface was achieved by the treatment of silica with γ‐aminopropyltriethxysilane or N‐phenyl‐γ‐aminopropyltrimethoxysilane. It was found that these amino groups on silica are readily reacted with living poly(isobutyl vinyl ether) (polyIBVE), which was generated with CF3COOH/ZnCl2 initiating system, and polyIBVE with controlled molecular weight and narrow molecular weight distribution is grafted onto the surface. By the termination of living poly(2‐methyl‐2‐oxazoline), which was generated with methyl p‐toluenesulfonate initiator, with amino groups on silica, polyMeOZO was also grafted onto the surface. The percentage of grafting of polymer onto the silica surface decreased with increasing molecular weight of the living polymer, because the steric hindrance of silica surface increases with increasing molecular weight of living polymer. Polymer‐grafted silica gave a stable dispersion in a good solvent for grafted chains. © 1995 John Wiley & Sons, Inc.

ABSTRACT:The grafting of polymers having controlled molecular weight and narrow molecular weight distribution onto chitosan powder by the termination of living polymer cation with amino groups on chitosan powder was investigated in heterogeneous system. The amino groups of chitosan powder successfully reacted with living poly(isobutyl vinyl ether) [poly(IBVE)] and poly(2-methyl-2-oxazoline) [poly(MeOZO)] cation with controlled molecular weight and narrow molecular weight distribution to give the corresponding polymer-grafted chitosan powders. The percentage of poly(MeOZO) grafting gradually increased and reached 24.5% after 4 days. The solubility of poly(MeOZO)-grafted chitosan in water increased with an increase in the amount of grafted polymer. It was suggested that grafting reaction of living polymer cation with chitosan powder proceeds from surface amino groups to inner amino groups of the powder with progress of the reaction. The mole number of grafted polymer chain on chitosan powder decreased with an increase in the molecular weight of the living polymer cation because the steric hindrance of functional groups of chitosan powder increased with the increasing molecular weight of living polymer.

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ABSTRACT:The grafting of polystyrene with controlled molecular weight and narrow molecular weight distribution onto the carbon black surface through the trapping of polymer radicals formed by the thermal dissociation of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated polystyrene (PSt-TEMPO) by the carbon black surface was investigated. PSt-TEMPO was prepared by living radical polymerization of St with the benzoyl peroxide/TEMPO system. When PSt having no terminal TEMPO moiety was heated with carbon black, no grafting of PSt onto the surface was observed. On the contrary, by the heating of PSt-TEMPO with carbon black in m-xylene at 125°C, PSt with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface: the percentage grafting of PSt (M n ϭ 3.2 ϫ 10 3 ; M w /M n ϭ 1.07) onto furnace black was determined to be 16.0%. On the basis of the above results, it is concluded that PSt radicals formed by the thermal dissociation of the COON bond between PSt and TEMPO are trapped by polycondensed aromatic rings of carbon black. The mole number of grafted PSt chains on the carbon black surface decreased with increasing molecular weight of PSt-TEMPO. PSt-grafted carbon black gave a stable colloidal dispersion in THF.

ABSTRACT:To graft polymers with controlled molecular weight and narrow molecular weight distribution, the grafting of polymers onto carbon black surface by the termination of living polymer cation with nucleophilic groups, such as amino groups and sodium phenolate and sodium carboxylate groups, introduced onto the surface was investigated. The introduction of amino groups onto the carbon black surface was achieved by the reduction of nitro groups introduced by the nitration of surface aromatic rings. Sodium phenolate and sodium carboxylate groups were introduced onto the surface by the treatment of surface carboxyl and phenolic hydroxyl groups with sodium hydroxide. These nucleophilic groups on carbon black readily reacted with living poly(isobutyl vinyl ether) (poly(IBVE)) cation, and poly(IBVE) with controlled molecular weight and narrow molecular weight distribution was grafted onto the surface. By the termination of living poly(2-methyl-2-oxazoline) (poly(MeOZO)) cation with these nucleophilic groups on carbon black, poly(MeOZO) was also grafted onto the surface. The mole number of grafted polymer chain on carbon black surface decreased with increasing molecular weight of the living polymer, because the steric hindrance of carbon black surface increased with increasing molecular weight of living polymer. The dispersibility of carbon black was remarkably improved by the grafting of polymers onto the surface.