Development of coated conductive nano-wires by use of self-organized block copolymers

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Block copolymers composed of poly(p-phenylene vinylene) (PPV) and poly(ethylene glycol) were synthesized. Pouring the copolymer solution into a polar solvent, which is a good solvent for PPV and a poor solvent for PEG, induced self-association of the obtained copolymers. Observation with a transmission electron microscope revealed the formation of nano-wires with the diameter of 10 nm and the length of more than 100 nm. The association of PPV segments was indicated from the UV and fluorescence spectroscopy. It was also found that the block copolymer could solubilize PPV homopolymer within the nano-wires formed in THF/water mixed solvent. Graft copolymers of PPV and PEG, which can be used as the self-association materials, were also successfully synthesized. From the above results, it is possible to prepare nano-wires having regulated shapes by adjusting the condition such as the composition and polymer concentration.Besides the PPV-based copolymers, other polymer associations were studied. The thermosensitive aggregation of poly(alkyl acylaminoacrylate)s was successfully controlled by replacement of various alkyl substituents. Urethane-modified PEG and other polyethers such as poly(propylene glycol) (PPG) and PEG/PPG copolymers were synthesized and the rheological properties under an electric field were examined in detail. The aggregation state of these polyethers can be reversibly changed in response to the electric field, which suggests the useful property of these polymers as an electrorheological fluid. Aqueous solutions of this kind of urethane-modified polyethers showed characteristic thermosensitive properties. The poly(alkyl acylaminoacrylate)s and polyethers responsive to temperature can be utilized as a component of nano-wires because of the controllability of association structures.