Yoshiyuki Ikeda

Gel formation driven by tunable hydrophobic domain: design of acrylamide macromonomer with oligo hydrophobic segment.

Nowadays, biomaterials with amphiphilic properties are undergoing remarkable development. Here, we present one such development, in which we prepared amphiphilic graft copolymers, with a main chain composed of hydroxyethyl acrylamide (HEAA), to introduce hydrophilicity, and a side chain composed of poly(trimethylene carbonate) (PTMC) to introduce tunable hydrophobicity. These macromonomers were created with a novel molecular design, which introduced a ring-opening polymerization by the hydroxyl end group of HEAA in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene, and were analyzed by (1)H NMR and gel permeation chromatography. The amphiphilic graft copolymers were shown to form a hydrogel, the swelling ratio of which was greatly influenced by the number of trimethylene carbonate units. These copolymers also exhibited the Tyndall phenomenon in aqueous solution; they aggregated spontaneously due to hydrogen bonding and hydrophobic interactions, and a sodium 8-anilino-1-naphthalenesulfonate (ANS) fluorescence probe was introduced into the hydrophobic domain. The solution property of ANS in the polymer solution was analyzed by fluorescence measurement and (1)H NMR. The maximum fluorescence wavelength of ANS shifted to shorter wavelengths as the degree of polymerization of the hydrophobic PTMC, the composition of the macromonomer, and the concentration of the copolymer increased. The resulting copolymer formed a polymer micelle structure due to the tunable hydrophobic domain formation in selected solvents. Therefore, these amphiphilic graft copolymers containing a PTMC segment are excellent candidates for use as hydrophobic drug delivery carriers.

Physico-chemical analysis on chemical bonding at adhesion interface between rubber and Pd alloy

Abstract Some spectroscopic analyses were carried out on the adhesive interface layers formed by cure-adhesion of natural rubber to electroless Pd and/or Pd–P alloys. The transmission electron microscopy revealed some clear images of the adhesion layer just at the interface between rubber and electroless-plating films of Pd and/or Pd–P alloys. The content ratio of Pd/S analyzed by energy dispersive X-ray spectroscopy changed gradually along the depth at the rubber–metal interface layer for Pd alloy, but was kept almost constant irrespective of depth for Pd–P alloy.