Differential Scanning Calorimetric Studies on the Melting Behavior of Water in Stratum Corneum

The melting behavior of water in human stratum corneum (s. corneum) has been studied by sing differential scanning calorimetry (DSC) in the temperature range from -40° to 20°C. The DSC thermogram was analyzed in terms of the amount of about water and the melting temperature of water in s. corneum. Extraction of the s. corneum with the mixed solvent of chloroform: methanol (2:1, v/v) or 0.5% sodium dodecyl sulfate aqueous solution decreased the bound water content, whereas extraction with water did not change the bound water content. The melting temperature of water in the s. corneum was lowered as the water contents decreased. Extraction of the water-soluble components from the s. corneum increased the melting temperature of water when the water contents were constant. The results suggest that 20–30% of water in the s. corneum is bound water interacting strongly with the protein or lipids in the s. corneum, and the excess of water over the bound water content is unbound water solubilizing the water-soluble components such as amino acids and urea in the s. corneum. The thermodynamic theory for freezing-point depression is favourably applied to the melting temperature change of the unbound water, which implies that the water-soluble components are present as an aqueous solution in the s. corneum. Measurements of the melting-point depression of water in s. corneum provides us the quantitative information on the amount of water-soluble components in the s. corneum. This technique is a sensitive and useful tool to evaluate the hydration behavior of s. corneum

Fractal Structures and Their Functional Properties(New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

この論文は国立情報学研究所の電子図書館事業により電子化されました

Menger Sponge-like Fractal Body Created with a Novel Template Method

この論文は国立情報学研究所の電子図書館事業により電子化されました。研究会報告細孔サイズ分布がN(r)αr^で記述される多孔質体:フラクタル立体の作製とその幾何学的性質について報告する。我々は、多孔質体の細孔に相当するテンプレート微粒子を作製・集積し、微粒子間の隙間に入れた重合性の溶液を重合させることで最終的に多孔質物質(ポーラスシリカ)を得た。多孔質体は空隙率85%、断面観察から50nmから30μmの約3桁にわたるスケールにおいて断面フラクタル次元D_=1.87であり、その幾何学的性質がフラクタル立体の数学的モデルMenger sponge(フラクタル次元D=log 20/log 3=2.73)に非常に近いこと(D～2.7)が分かった。さらにフラクタル立体のDの制御方法も確立した(D=25～27)。フラククル立体により空間次元の制御が可能となるため、様々な実験への応用が期待される

Potential Application of Poly(N-isopropylacrylamide) Gel Containing Polymeric Micelles to Drug Delivery Systems

We have investigated rapidly thermo-responsive NIPA gel containing polymer surfactant PMDP (NIPA-PMDP gel) as a potential drug carrier using (+)-L-ascorbic acid as a model drug. In the NIPA-PMDP gel system micelles of polymer surfactant PMDP are trapped by the entanglement of polymer chains inside the gel networks. Therefore, in principle the gel system tightly stores targeted drug in the micelles and rapidly releases controlled amount of the drug by switching on-off of external stimuli such as temperature or infrared laser beam. In our investigation on release profile, the NIPA-PMDP gel system showed completely different releasing behavior from that of the conventional NIPA gel. The NIPA-PMDP gel released rapidly all loaded (+)-L-ascorbic acid above the phase transition temperature (ca. 34 ℃), while slowly released the corresponding amount of the drug below the temperature. In contrast, the conventional NIPA gel released more slowly limited amount of the drug above the phase transition temperature while similarly did to the NIPA-PMDP gel below the temperature. The release profile of the NIPA-PMDP gel seems to be governed by only kinetics of volume phase transition of the gel network but not by the hydrophobic domains of the micelles probably because of too hydrophilic nature of (+)-L-ascorbic acid

Formation mechanism of super water-repellent fractal surfaces of alkylketene dimer

Alkylketene dimer (AKD), a kind of wax, has been known to form fractal surfaces spontaneously, and to show super water-repellent property. In order to understand further the super water-repellency of the AKD surfaces and to elucidate the mechanism of spontaneous formation of the fractal structures on the wax surfaces, a pure and a mixed AKD samples were employed to make the surfaces by the melt-solidification method. Time-dependent contact angles of water droplets on the AKD surfaces cured at several temperatures were systematically measured. It was found that spontaneous formation of super water-repellent surfaces was thermally induced quite effectively. For example, it took about 6 days for the pure AKD surface to show the super water-repellency at 40 oC but did just 1 hour at 50 oC. The fractal dimension of the mixed AKD surface with super water-repellency was calculated to be 2.26 from the SEM images by the box-counting method which should be reasonably compared with 2.29 of pure AKD surface. The mechanism for the spontaneous formation of fractal structures was discussed from the results of the time-dependent contact angles, differential scanning calorimetric (DSC) curves and X-ray diffractometric (XRD) patterns. It has been made clear that the fractal AKD surface and its super water-repellency result from the phase transformation from the metastable state to the stable one of the AKD crystals

Super water-repellent poly(alkylpyrrole) films having environmental stability

We present electrochemical synthesis of super water-repellent poly(alkylpyrrole) films which exhibit excellent environmental stability in terms of contact angle (>150°) for water. The poly(alkylpyrrole) films synthesized under an optimized electrochemical condition consisted of thousands of micro-scaled ‘needles’ which densely aligned by shoulder to shoulder. The surface of the aligned ‘needles’ was analyzed by a box-counting method, to be a fractal structure with a dimension of 2.18