Fluoroalkanoyl peroxide was found useful for the synthesis of fluoroalkyl end-capped oligomers having COOH, SO₃H, O=C-NR₁R₂, OH, betaine segments, phosphorous segments and blocked-isocyanato segments. The fluoroalkyl end-capped oligomers were generally soluble not only in water but common organic solvents as well. These oligomers were highly surface active, showing very low surface tensions and clear break points, as in the case of low molecular weight fluorinated surfactants. Self-organization thus occurs to form molecular aggregates. Based on light scattering studies, fluoroalkyl end-capped oligomers having COOH formed ellipsoidal micelles. Fluoroalkyl end-capped oligomers with hydroxy or betaine segments gave rise to gelation owing to hydrophobic interaction of end-capped fluoroalkyl segments in addition to the hydrogen bonding and/or the ionic interaction of betaine segments.
Moreover, as some examples of interesting properties of fluoroalkyl end-capped acrylamide type oligomers, the unique binding power of Ca²⁺ or Cr³⁺, selective recognition of organic color material having -NH₂ or -NMe₂ groups such as methylene blue and/or luminol, and the immobilization of cytochrome c are discussed. These features may be due to molecular aggregates produced by the interaction between end-capped fluoroalkyls.

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Physico-chemical properties of sugar-based surfactants, such as alkyl glucosides, alkyl maltosides, sucrose monoalkanoates, and alkanoylglucosides, were reviewed with attention directed primarily to anomeric effects of the head group sugar. Phase behaviors of surfactant solid and surfactant-water 2-component systems for α-anomer of alkyl glucosides differed considerably from that of β-anomer. Chain length effects of the hydrophobic group on phase behavior of alkyl glucoside-water system were studied for β-anomers and a liquid-liquid phase separation region was confirmed to exist for decyl β-glucoside (0.1-17 wt%) but for octyl and nonyl β-glucoside. The growth of micelles of decyl β-glucoside would thus appear to be promoted by increse in surfactant concentration and micellar network structure was noted to form at above 17 wt% solution. The size and shape of micellar aggregates for octyl glucoside, dodecyl maltoside, and octanoylglucoside demonstrated significant anomeric effects.

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A new cholesteric liquid crystals that respond quickly to stimuli such as temperature change or photoreaction of a doped compound in a liquid crystalline phase were found and stable molecular ordering below 80°C in the solid state brought about by rapid cooling from the liquid crystalline phase was noted. By changing the temperature at which rapid cooling start or degree of photoisomerization of photochromic compounds, colors from the visible spectral region reversibly fixed as interference colors. The compounds exhibited surface-directed self-assembly in a helical molecular ordering to form optically reflecting solid film on spin-coating from solution. All these may be considered properties of liquid crystals of medium-molecular-weight with over 1000 mass units. Through these properties, it is possible to obtain a re-writable full color recording in a photon or thermal mode.

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Examination was made of the development and properties of chemically cleavable surfactants.
Chemically cleavable surfactants possessing dioxolane, dioxane ring, noncyclic acetal group and carbon-nitrogen double bond were synthesized and found to easily undergo hydrolytic decomposition by acid.
Many of these surfactants were noted to have good surface activity and undergo biodegradation in addition to acid-sensitivity.
Bis (sodium sulfonated ester) and bis (ammonium bromide) surfactants were synthesized and found to exhibit alkali-sensitivity, surface activity and biodegradability.
Ozon-cleavable surfactants bearing carbon-carbon double bonds were also produced and noted to have good surface active properties and biodegradability.

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Various amphiphilic block copolymers (polymer surfactants) possessing hydrophilic and hydrophobic segments were designed, prepared, and examined for stimuli-responsive selforganization in water. New polymer micelles or physical gels that would have this property were made by intermolecular hydrophobic interaction. Recent advances and related topics are initially summarized in this paper.
Well-controlled block copoly (vinyl ether) s were synthesized in this study by living cationic polymerization of vinyl ethers with various functional groups. Not only hydrophilic polyalcohols and hydrophobic poly (alkyl vinyl ether) s, but thermally-responsive polymers with oxyethylene units as well were used as segments of diblock copolymers. When aqueous polymer solution was heated, characteristic physical gelation occurred in a certain temperature range corresponding to the particular properties of the segments. As other stimuli, the addition of selected organic compounds and H⁺ to the solution containing diblock copolymers was also examined as a means for obtaining physical gels via a mechanism similar to that in thermally-responsive systems.

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Poly (ethyleneoxide) /poly (propyleneoxide) triblock copolymers, with the commercial name of Pluronics are receiving increasingly more attention for their low toxicity and stimulus compared to other nonionic surfactants. Aqueous solution of these copolymers have unique properties. The capacity of micelle and gel formation is determined considerably by temperature. Various physical properties and applications of these copolymers are discussed.

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The synthesis of fluorinated silane coupling agents having methoxy, ethoxy, or isocyanate groups was conducted in the present study and their applications to surface modification of glass and dental material (bovine tooth) are discussed.
Methoxy-type silane coupling agents were prepared by hydrosilylation of trichlorosilane with fluoroalkylated olefins, followed by reaction with sodium methoxide. Isocyanate-type coupling agents were obtained by reactions of chloro-type coupling agents with silver cyanate in benzene. Glasses modified with fluorinated coupling agents showed high repellency toward water and oleic acid. Fluorinated silane coupling agents possessing three methoxy or isocyanate groups formed fluorocarbon layers having high stability in acid and oxidant on glass surfaces. In vivo and in vitro experiments indicated very little plaque to accumulate on bovine tooth surfaces modified with the isocyanate-type coupling agent. Fluorinated silane coupling agents should thus prove useful as surface modifiers for the promotion of oral health.

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Direct evidence has been presented for condensed phase formation in adsorbed monolayers at surfactant solution surfaces, which is quite the same as phase transitions from expanded to condensed phases in spread monolayers by compression. It thus follows that there is no clear boundary between adsorbed and spread monolayers.
However, there are many different modes of relaxation in spread monolayers ouing to the greater non-equilibrium nature of spread monolayers during compression compared to adsorbed monolayers.

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Photoreactions in Langmuir-Blodgett (LB) films were studied with special attention directed to structural changes of LB films accompanied by the photoreactions. First, a counter concept of free volume is presented. Three-dimensional cone-shaped structures were developed with trans-to-cis photoisomerization in polyion complex LB film of a water-soluble amphiphilic azobenzene. The structures alternately appeared and disappeared by illumination with UV and then visible light. The concept of free volume was found not to hold in the present case. Photoinduced J-aggregate formation of non-photochromic and photochromic dyes is discussed. Reversible photoisomerization of azobenzene in mixed LB films of azobenzene and dyes triggered irreversible J-aggregate dye formation. J-aggregate formation was accompanied by irreversible large morphological changes of the films. The photoisomerization of azobenzene served to induce self-organization of dye molecules. The photopolymerization of amphiphilic diacetylenes was investigated in LB films. This process was found to consist of blue-red, red, and yellow phases based on the spectral change. This change was found to depend on molecular orientation in the LB films. During the blue-to-red transition, the LB films showed considerable morphological change.

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Aggregate properties of aqueous solutions of surfactants, characterization of model membranes, methods for the preparation of vesicles and vesicle-forming surfactants are reviewed in the present study. Nonionic amphiphiles are widely regarded as synthetic tailor-made lipids in consideration of their safty and ease of molecular structural design. In search for vesicle-forming substances with safe physiological properties, good storage stability and ease of preparation, poly (oxyethylene) (10) hydrogenated castor oil was found to meet these requirements. Vesicle formation of poly (oxyethylene) hydrogenated castor oil and physico-chemical properties in aqueous dispersion are discussed in the following.

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Phase transition from a positive to negative-curved self-organized structure was noted to occur in a binary water/polyoxyethylene-type nonionic surfactant system with decrease in the number of ethyleneoxide (EO) units at constant temperature. Effective cross sectional area per each surfactant decreased with reduction in the EO chain length. The mechanism for phase transition is discussed based on the revised packing parameter theory. The effects of oil type on the surfactant layer curvature are explained as due to penetration and/or swelling of oil. Due to the oil effect, surfactant changes from water- to oil-soluble in a narrow range of temperature or EO-chain length in the presence of oil. This is the reason for the appearance of HLB temperature or PIT in water-oil system.

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Interactions of liposomes with detergents and physicochemical properties of liposomes were reviewed. Several amphiphiles that produce liposomes by themselves or form liposomes only by mixing two amphiphiles are initially discussed and then solubilization of liposomes by detergents, formation of liposomes from mixed micelles on removal of the detergents, mechanism of micelle-vesicle transition, and method for regulating vesicular size are considered in regard to the micelle-vesicle transition mechanism. ESR spectroscopy, hyperfine splitting of 2, 2, 6, 6-tetramethylpiperidine-N-oxyl dissolved in octylglucoside-containing vesicles and order parameters of 5-doxylstearic acid incorporated in vesicles, was useful for obtaining the properties of detergent-containing liposomes. ¹H NMR spectra of the choline N-methyl group in internal and external monolayers of phosphatidylethanolamine/lysophosphatidylcholine (LPC) vesicles indicated LPC to possibly prefer external monolayers of lipid and the presence of internal monolayers to be essential for vesicle stabilization.

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Lipid microspheres (Lipid emulsions) should prove useful colloidal drug carriers in various therapeutic applications and as parenteral delivery systems owing to their ability to incorporate lipid-soluble drugs in dispersing phases. Lipid microspheres are o/w emulsions similar to commercially available fat emulsions. The oil droplets in the dispersing systems function as drug containing reservoirs. Surface modification of oil particles in emulsions adjust drug release rate and affinity for target sites. Recent advances in the development of lipid microspheres are discussed and comparison is made with conventional preparations.

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Dendrimers, which are dendritic polymers, behave as amphiphilic molecules, if their core, repeating, or terminal unit is properly modified. Amphiphilic dendrimers are classified as head-tail block, surface block, and layer block dendrimers, star-shaped dendrimers, dendritic star polymers, polymer dendrons, and the like. Head-tail block and surface block dendrimers have bending points, that is, critical micelle concentrations on surface tension-concentration curves and aggregate into micelles in solution. Amphiphilic dendrimers also form bilayers, liquid crystals, and Langmuir monolayers. Amphiphilic dendrimers have the unique feature of remarkable molecular ordering in the film adsorbed on a solid surface, in contrast to those that are isotropic such as the poly (amido amine) dendrimer. The encapsulation of solvents and/or small molecules differs according to the blocks of amphiphilic dendrimer.

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Lipid emulsions consisting of triglyceride cores and surface monolayers of phosphatidylcholine (PC) are physical models for plasma lipoproteins. Despite similar surface compositions, emulsion surface monolayers are more rigid in the acyl chain region but more hydrated in the interfacial region compared to bilayers. These features appear to be attributed to surface-core interactions in emulsions in which acyl chains of surface PC interdigitate to some extent with those of core lipid. Emulsion particles show quite different behavior from bilayer vesicles with respect to physico-chemical stability and physiological metabolism, indicating emulsion surface-core interactions to be importantly involved in physico-chemical and biological functions of lipid emulsions.

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The basic concept of small-angle X-ray and neutron scattering (SAXS, SANS) has been described by way of applications of polymer micelle systems. SAXS and SANS provide information on the size, shape and surface nanostructure of micelles. Based on model calculations and contrast variation in SANS, density inhomogeneity within the particle can be assessed. SAXS and SANS are highly useful for the study of surfactant micelle.

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Recent developments in NMR experiments for surfactant systems are reviewed, especially new techniques using pulsed-gradient spin echo for studying the structures of vesicles and emulsions and ²H NMR measurements under shear flow on lyotropic liquid crystals.

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Scanning probe microscopy (SPM) is widely used for characterizing surface morphology and properties. In the SPM family, atomic force microscopy (AFM) is useful for insulating materials under various atmospheres. And AFM facilitates the study of aggregation structures of surfactants on solid surfaces. In this review, SPM, especially AFM, are briefly explained and AFM images of surfactants are presented. Molecular arrangements of surfactant single crystals were visualized and found consistent with the results of x-ray diffraction. Heterogeneous growth and self-repair of surfactant aggregates at an aqueous solution/silica interface could be observed by in situ AFM. The morphology of various surfactants aggregate on solid surfaces was studied by soft contact AFM under various conditions.

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This article reviews applications of surface forces measurement for characterizing interactions of molecular assemblies with overview given in Table 1. Measurement techniques using a surface force apparatus and a colloidal probe atomic force microscope described in a concise manner, and the results of detailed researches on functionalized surfactant assemblies are presented. 1) Surface forces measurement provided evidence for spontaneous vesicle formation of an ammonium surfactant with an acetate counterion. 2) The mechanism of fusion and aggregation of surfactant vesicles in the presence of salt (NaCl) was clarified. 3) Interactions between bilayers of various biological phospholipids were found to be attractive van der Waals and repulsive steric hydration forces in pure water and monovalent salt solutions. 4) Hydrogen-bonding interactions between glycine head groups were directly demonstrated. 5) Interactions between LB films of metal-chelating lipids ; pH dependence reflected different protonation states of iminodiacetic acid groups, and Cu²⁺ complexation with them. 6) The effects of surfactant on the particle - bubble interactions between hydrophilic and hydrophobic silica particles and an air bubble were examined.

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Organic pigment thin films were prepared using a surfactant with an azobenzene group (AZPEG) which loses its amphiphilic function by reduction. Electroless plating on base metals was done by immersing base metal plates in an organic pigment dispersion prepared with AZPEG. Contact plating of noble metals was carried out by immersing the substrate and aluminum plates in the pigment dispersion, in which the two plates were short-circuited. Film formation was found to depend on pH of the dispersion and film thickness to increase with immersion time. The rate of film growth depended on the concentration of AZPEG, since free AZPEG hinders the deposition of pigment. Scanning electron micrographs of the film indicated uniform thickness mainly composed of pigment particles. Results of film formation for various kind of pigments are listed. Methods for film reinforcement are proposed.

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The roles of surfactant in polymerization of the conducting polymers and surfactant-introduced conducting polymers were examined. Particular, attention was directed to our research on electrochemical reactions of polymers and feasibility as energy storage materials. Monomers of conducting polymer dissolve in the hydrophobic domain of surfactant micelles in aqueous solution and surfactant bilayers on a substrate. Surfactant hydrophilic-hydrophobic characterization makes possible structural control of electrodeposited polymer film. Polypyrrole film, a conducting polymer, with perpendicular orientation and high ion diffusivity, is formed by electropolymerization in the presence of micelles. This film can be electropolymerized even on a substrate of non-noble metal having low electronic conductivity, using an anionic surfactant. The simultaneous formation of two-layers consisting of oxide film with a high dielectric constant and polypyrrole film on valve metals such as aluminum is discussed.

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Spatial arrangement of the ruthenium dipyridyl complex and ferrocene derivative in hetero-deposited redox polymer Langmuir-Blodgett (LB) films was carried out for direction control of photocurrent flow produced by photoinduced electron transfer reaction and for high quantum efficiency. Two hetero-deposited structures were obtained by varying the deposition order of the redox polymer monolayers by the LB technique. Cyclic voltammograms of hetero-deposited redox polymer LB films exhibited current rectifying and charge storage properties. Light irradiation led to anodic photocurrent of hetero-deposited redox polymer LB films consisting of Ru copolymer LB film as an inner layer and Fc copolymer LB film as an outer layer on the ITO (Fc/Ru/ITO) electrodes. On the other hand, cathodic current was observed at the reverse layered structure (Ru/Fc/ITO) electrodes. The direction of photocurrent flow depended on the deposition order of redox polymer LB films on the ITO electrode. Photocurrent quantum efficiency of 5.9% of the hetero-deposited redox polymer LB film was achieved. High photocurrent conversion efficiency is explained by inhibition of recombination of photoinduced charge separation due to hetero-deposited LB film structures.

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Adsorption-induced self-organization is a new concept for “wet process” techniques for preparing highly ordered molecular adlayers by spontenious adsorption in aqueous solution. The essential step is a controlled “mild” adsorption, which makes possible rapid surface diffusion and adsorption/desorption equilibrium. To conduct “mild” adsorption, the choice of substrate and setting of electrode potential are most possible. STM visualization of highly ordered molecules provides fundamental data on intermolecular interactions.

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Molecular-sensing methods based on signal transduction at membrane interfaces and in biological systems developed at this laboratory are introduced as the following : 1) ion-channel sensors, 2) molecular mechanism for ion-selective charge separation; basis for ion-sensing, 3) methods for functional group recognition by chemically modified STM tips, 4) surface gravimetry based on molecular recognition at the interface of crystal-growth and 5) fluorescent probe molecules for clarification of cellular mechanisms.

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Intercalation of inorganic materials into organized organic assemblies provides possibility for developing new functional materials possessing superior physicochemical properties. A composite material consisting of Prussian blue intercalated into photo-responsive organic molecules (azobenzene-containing multibilayer vesicles) was made. Photoisomerization of the film was attended with geometrically confined structural change within the vesicles as reflefted by changes in dipole moment and electrostatic field. It was consequently possible to control the magnetic properties of the new material by photo-illumination, as well as magnetic properties of photo-isomerizable nano-film containing iron oxide particle by photoillumination at room temperature.

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Biomimetic processing of ceramic materials was carried out in the present study using 2-dimensional assembles of organic surfactants. Induced crystallization of nano-particles and epitaxial growth of a thin film under Langmuir monolayers are discussed. The authors established a novel method of micro-patterning of ceramic thin films using patterned templates.

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A variety of bola-form amphiphiles (bolaamphiphiles), in which sugar, peptide, or nucleobase moieties are connected to both ends of a hydrocarbon spacer, were synthesized. These compounds self-assembled in aqueous solution to form thermally stable, nanometer-scale high-axial-ratio microstructures (HARMs), such as helical fibers, tubular fibers, and double-helical ropes. Size distribution of the structures was essentially the same as that of self-assembled fibrous structures like collagen fibers, flagella, and actin fibers and morphology was found to strongly depend on chain length and even-odd carbon number of used oligomethylene spacers. Molecular arrangement and hydrogen bond networks within HARMs were investigated by FT-IR, XRD, and AFM. Interlayer and intralayer interactions of the monolayers were noted to be major determinants of fiber morphology. HARMs are constructed hierarchically in a manner similar to biological structures.

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Hyperbranched polymers or dendrimers have been of considerable interest since the mid 1980s. Nanocomposites consisting of dendrimers and various metal nanoparticles have been synthesized for use in the preparation of highly functional materials such as substrate-selective catalysts and chemical sensors. The synthesis and applications of dendrimer-metal nanocomposites mainly for poly (amidoamine) dendrimers are discussed in this paper.

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The solubilization of organic molecules in surfactant molecular assemblies may be controlled effectively by electrochemical reactions using redox-active surfactants. In this study, several aromatic compounds were solubilized in aqueous micellar solution of ferrocene-modified nonionic surfactant (11-ferrocenylundecyl polyoxyethylene ether : FPEG) and the effects of redox reactions on solubilization were examined. The solubilization equilibrium constant (K) of the solutes in FPEG micelles, which represents the distribution of solubilizates between micelles and bulk solution, was noted to decrease with the oxidation of ferrocenyl moieties of FPEG molecules, but increase with reduction of ferrocenyl moieties. Electrochemical control of vesicle formation and applications for solubilization control were investigated using aqueous mixtures of a ferrocene-modified cationic surfactant (FTMA) and anionic sodium dodecylbenzene sulfonate (SDBS).

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