Yasuhiko Yagi

Swelling behaviours of N-alkylacrylamide gels in water: effects of copolymerization and crosslinking density

N-isopropylacrylamide (NIPA)/N-n-propylacrylamide (NNPA) copolymer gels of various molar ratios were prepared by radical polymerization and the relationship between the swelling behaviour of the gels and the copolymerization ratio was studied experimentally. The effect of a crosslinking point on the swelling behaviour of the NIPA gels was investigated by preparing the gels with various crosslinking densities. The results of our experiments revealed that the transition temperatures of the NIPA/NNPA copolymer gels were changed in proportion to the monomer ratio used in copolymerization and that the crosslinking density strongly affected the swelling ratios but not the transition temperatures of the gels.

Density dependence of the molar absorption coefficient—Application of the beer-lambert law to supercritical C02—Naphthalene mixture☆

Abstract Infrared absorption spectra of naphthalene in supercritical carbon dioxide (C0 2 ) solutions of various concentrations were measured at 318.15 K at various pressures. The molar absorption coefficient of naphthalene in supercritical CO 2 was found to be dependent on the density of C0 2 . As the density of CO 2 increased, a red shift of peak wavenumber of the C-C vibration (quadrant stretching) were observed. This suggests that the molecular vibration of naphthalene in supercritical C0 2 was affected by the fluid density.

Density dependence of fermi resonance of supercritical carbon dioxide

Abstract Infrared spectra of supercritical carbon dioxide were measured at various pressures and temperatures. The Fermi resonance absorbance of supercritical CO2 was influenced by pressure and temperature. The absorbance data revealed that the density dependence of Fermi resonance in the vicinity of the critical point was different from that in the region far from the critical point and was found to be related to that of the isothermal compressibility.

Non-radiative energy transfer in N-isopropylacrylamide gel

Abstract Non-radiative energy transfer from donor to acceptor probes attached to the network chains of an N -isopropylacrylamide (NIPA) gel was investigated in water at various temperatures through fluorescence spectrum measurements. Naphthalene or biphenyl was used as a donor, and pyrene as an acceptor. Two types of doubly labeled NIPA gels (NIPA/2-vinylnaphthalene/pyrenylacrylamide and NIPA/4-vinylbiphenyl/pyrenylacrylamide) were prepared by copolymerization. The non-radiative transfer was observed for both gels. The ratio of emission intensity from donor to that from acceptor was strongly dependent on temperature, which indicates that the non-radiative energy transfer in doubly labeled NIPA gels could be controlled by means of the volume change with temperature.