crosslinker are controlled, it is technically possible to prepare a gel membrane reflecting the specific color at a certain temperature. This method to prepare the interconnecting porous gels will give us the potential to study appropriate smart gels that may have interesting applications, such as in tunable optical filters, actuators, and sensors. Studies to confirm this are underway. ExperimentalSynthesis of Colloidal Crystals as Templates: To prepare the closest-packed colloidal crystals, a 15 wt.-% aqueous solution of silica spheres, having a diameter of 291 nm as determined from SEM measurements, was used. The growth of the crystal by the gravity sedimentation method was conducted in a flat Petri dish at 20 C. The stable dried crystals were obtained within 1 week as the water evaporated, and then completely dried in vacuo at 60 C. It is generally accepted that the crystalline arrays produced by the gravity sedimentation method have a cubic close-packed structure containing polycrystalline domains, similar to that of a natural opal. The thickness of the crystal can be easily controlled by the colloidal concentration and the iterative treatment. On the other hand, fine ordered crystals were created by the solvent evaporation method as follows: the colloidal suspension (ca. 15 wt.-%) was dropped onto a clean microscope slide and was placed in a thermostatic chamber at 90 C, in which the solvent gradually evaporated. A high quality crystal can be prepared with a thickness of up to 1 mm.Synthesis of Porous Hydrogels and Cylindrical Hydrogels: The thermosensitive gels were prepared by free-radical polymerization as follows. First, N-isopropylacrylamide (NIPA, 11.3 g), N, N¢-methylene bis(acrylamide) (0.513 g) as a crosslinker, and benzoylperoxide (0.048 g), the initiator, were dissolved in degassed and nitrogen-saturated 1,4-dioxane to a final volume of 50 mL. The solution was then infiltrated into the colloidal crystals in a Petri dish, and the polymerization was conducted at 60 C for 40 h. Afterwards, the samples were immersed in a 5 wt.-% HF aqueous solution to remove the SiO 2 . The gels for a swelling measurement were prepared in micropipettes of 100 lm diameter. The resulting porous gels and the cylindrical gels were washed carefully with distilled water for 1 week.Measurements: The swelling measurement was carried out by monitoring the diameter of the cylindrical gel in water. The temperature was controlled by using a temperature control system with circulating water. The reflection spectra were obtained by an Ocean Optics USB2000 fiber optic spectrometer [13] We did not use a macroporous gel to determine the swelling behavior.Therefore, a small difference in swelling size between the porous gel and cylindrical gel seems to be present, because the quantitatively different values were obtained in the wavelength of the peak of the reflection spectra from a porous gel as a function of temperature in Fig. 4b. Nevertheless, the experimental results qualitatively prove our description.

Various polymeric phosphonium salts and the corresponding low‐molecular‐weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part. Compounds with the longest alkyl chain (octyl) studied were found to exhibit particularly high activity, and this finding may be ascribed to the contribution of the increased hydrophobicity of the compounds to the cidal activity. © 1993 John Wiley & Sons, Inc.

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Polydomain films of liquid crystalline polymer (MACB- AB6) with low content (6 mol %) of azobenzene units were prepared and irradiated with linearly polarized light at 366 nm, thus inducing an alignment of the photochromic side groups as well as the nonphotoactive mesogens, the cyanobiphenyl groups. An induced order parameter, S, was obtained from polarized UV and IR spectroscopy, and it increased with increase in temperature at first and then decreased due to phase transition. The effect of light intensity on the alignment behavior has been investigated in detail. Alignment change can take place even for a low intensity (0.7 mW/cm2) of irradiation light. Irradiation light at high intensity induced alignment as well as a phase transition at relatively low temperature. A higher saturation order parameter and faster achievement of the order parameter were obtained, since a higher concentration of cis-azobenzene was produced when the film was exposed to polarized light with a higher intensity. This is due to the angular-dependent absorbance of irradiation light by the azobenzene moieties.