No abstract

ABSTRACT:The responses of electric resistance of composites prepared from amphiphilic polymer-grafted carbon blacks to contamination in solution and solvent vapor were investigated. The electric resistance of the composite prepared from poly(N-isopropylacrylamide) (PNIPAM)-grafted carbon black drastically increased when the composite was dipped in n-hexane containing contamination, such as methanol, THF, dioctyl phthalate, and chloroform, and returned to the initial resistance when it was transferred to dry air. The logarithm of the electric resistance of the composite was linearly proportional to chloroform concentration in n-hexane. The electric resistance of the composite drastically increased in organic polar solvent vapor, such as methanol, THF, and chloroform and returned to the initial resistance when it was transferred to dry air. But the response to non-polar solvent vapor, such as n-hexane, was very small. The logarithm of electric resistance of the composite was linearly proportional to humidity. In addition, electric resistance of the composite prepared from poly(diethylacrylamide) (PDEAA)-grafted carbon black also drastically increased when the composite was dipped in n-hexane containing contamination, such as methanol, trichloroethane, THF, chloroform, and benzene, and returned to the initial resistance when it was transferred to dry air. Based on the results, it was found that the composites could be used as a novel contamination sensor in n-hexane and gas sensor.

ABSTRACT:To improve the dispersibility of carbon microcoil (CMC) in solvents and polymer matrices, the grafting of copolymer containing vinyl ferrocene (VFE) onto surface by ligand-exchange reaction with ferrocene moieties of the copolymer and polycondensed aromatic rings of CMC was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with vinyl monomers, such as methyl methacrylate (MMA) and styrene (St), using 2,2 0 -azobisisobutyronitrole as an initiator. It was found that by heating of CMC with poly(VFE-co-MMA) and poly(VTE-co-St) in the presence of AlCl 3 and Al powder as catalyst, these copolymers were grafted onto the surface: the percentage of grafting reached to 64.2%. On the contrary, in the absence of AlCl 3 , no grafting of the copolymer was observed. The grafting of polymers onto the CMC surface was confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR), thermal decomposition gas chromatography-mass spectroscopy (GC-MS) and fieldemission scanning electron microscope (FE-SEM). Therefore, it is considered that the copolymer was grafted onto CMC surface by ligand-exchange reaction with ferrocene moieties of the copolymer and polycondensed aromatic rings of CMC. The polymer-grafted CMC gave a stable dispersion in solvents for grafted polymer.

ABSTRACT:Carboxyl groups were successfully introduced on carbon microcoil (CMC) surface by the treatment with nitric acid. The carboxyl group content increased with increasing reaction time and reached to 1.34 mmol/g after 10 h. Poly(ethylene glycol) (PEG) was grafted onto the CMC surface by the reaction of carboxyl groups with terminal hydroxyl groups of PEG in the presence of condensing agent such as N,N 0 -dicyclohexylcarbodiimide or Lewis acid catalyst such as scandium (III) trifluoromethanesulfonate. Carboxyl groups on CMC surface have ability to initiate the cationic polymerization of vinyl monomers, such as isobutyl vinyl ether and N-vinylcarbazole and the corresponding polymers were grafted onto the surface. By grafting of polymers onto the surface, the entanglement of CMC was effectively destroyed and polymer-grafted CMC uniformly dispersed in good solvents for grafted polymer and silicone rubber. The inductance, capacitance, and resistance of conductive composite prepared from polymer-grafted CMC responded to acetone vapor. The inductance of the composite from polymer-grafted CMC increased in acetone vapor, and returned to initial value when it was transferred into air. The capacitance and resistance of the composite decreased in acetone vapor, and returned to initial value when it was transferred into air.

No abstract