Novel nanocomposite (NC) gels with
zwitterionic characteristics
were prepared by in situ free-radical polymerization of sulfobetaine
monomers in the presence of exfoliated clay platelets in aqueous media.
Two specific sulfobetaine monomers, N,N-dimethyl(acrylamidopropyl)ammonium propanesulfonate and butanesulfonate,
were selected on the basis of the interactions between the monomers
and clay, which result in uniform aqueous solutions of low viscosity
and gel formation without using an organic cross-linker. The resulting
NC gels with polymer–clay network structures were insoluble
in NaCl solution or hot water, unlike conventional physically cross-linked
gels. Also, NC gels with high mechanical properties and well-controlled
thermosensitivities were effectively prepared by copolymerization
with a small amount of N,N-dimethylacrylamide.
The copolymer NC gels were uniform and simultaneously showed high
stretchability, tough mechanical properties, and well-defined upper
critical solution temperature (UCST) phase-transitions. Furthermore,
the tensile mechanical properties and UCST were controlled over a
wide range by altering the clay concentration and copolymerization
ratio.
Two new silver nanoclusters, formulated as Ag42(SBut)24 and Ag61(SC6H11)40Cl were prepared by a NaSbF6-mediated two-phase ligand exchange method. A size conversion from Ag42 to Ag61 were achieved via cyclohexanethiol etching.
To obtain organic nanowire sensors with high sensitivity and rapid response times, based on the inducement effect of surfactants during in situ polymerization, nanostructured polyaniline composites are obtained by using a chemical oxidation method by adding a small amount of surfactant. A casting method is employed on interdigitated carbon electrodes. The gas sensitivity to a series of chemical vapors is examined at room temperature. The results indicate that polyaniline with regular nanowire structure is obtained when succinic acid is added. The gas sensitivity and response rates of a film with nanowire structure are much better than those of conventional polyaniline films produced by means of organic solution spin coating methods. The film described in this work shows good selectivity to trimethylamine and other related gases and, the reaction being reversible with the use of high-purity nitrogen.
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