Gecko toes have pads with countless cilia under their foot, and it is said that the van der Waals force between the cilia and the wall generate the adhesion force to climb up vertical walls. Recently, we found that a polymer having long alkane side chains show strong van der Waals interaction and thus show very strong adhesion to polyethylene which usually does not adhere to other materials. The adsorption force is generated by constructing pseudo crystal between the surface polyethylene molecules and the long alkane chain of polymer side chains. We name this interaction force “Crystalline Supramolecular Interaction”. In this article, I will report about the generation mechanism of the Crystalline Supramolecular Interaction and the polyethylene surface modification functions with using the interaction.

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In recent years, self-assembly beyond the molecule, which combines biological chemistry, materials science and nano- or micro-meter scale technology, has attracted much attention. Fundamental research on the self-assembly of non-molecular systems such as metal nanoparticles, which are regarded as “artificial molecules”, can enhance our understanding of the concept of self-assembly. Herein, we propose a robust strategy for the dimension-controllable fabrication of nano-assemblies of nanoparticles through tuning inter-particle interactions using suitable surface ligands. The formation of hydrogels consisting of a fibrous assembly of quantum dots (QDs), multi-layered gold nanoparticles (AuNPs), and AuNP vesicles as well as their prospective applications are investigated. The development of AuNP vesicles with hollow structures and special optical properties motivated by biomimetics has been extensively explored in medicinal chemistry for potential application to drug delivery systems (DDSs) and as a platform for surface-enhanced Raman scattering as an analytical tool. Novel self-assembly strategies using Janus-like nanoparticles are also discussed.

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Lipid molecules form anisotropic self-assembled structures such as worm-like micelles or lipid bilayers. Recently the authors have successfully introduced and immobilized uniaxially-oriented lipid bilayers of poly(dodecyl glyceryl itaconate) (PDGI) into the polyacrylamide (PAAm) gel matrix to obtain stable gel-bilayer composites (called PDGI/PAAm gels) with anisotropic structure and functions, such as unidirectional swelling or anisotropic diffusion. One question about this complex is why such a dynamic lipid bilayer structure can be well-stabilized in PAAm gels. In this paper, we focus on the bilayer structure of the PDGI/PAAm gels. In the first part, the stabilization mechanism of lipid bilayers in the gels, due to hydrogen bonding between PDGI and PAAm, is discussed. In the second part, structure transition and function modification of the PDGI/PAAm gels by insertion of more lipid molecules into bilayers is investigated.

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Hydrophobically grafted amphiphilic polymers form nanogels with three-dimensional networks generated by physical cross-linking of the polymer chains in dilute aqueous solution. Compared with other nanoparticles, such as polymer micelles, which have a densely packed polymer inside the core structure, nanogels are able to stably trap proteins and DNA/RNA inside their nanospace. This property allowed development of nanogels with a particular focus on biomedical applications, including drug delivery systems. We reported about physically crosslinked nanogels using self-assembly of cholesterol-bearing polysaccharides. More recently, self-assembled nanogel formation has also been demonstrated with other associating graft copolymers such as hydrophobized poly(amino acids) and hydrophilic synthetic polymers onto which associating groups were partly grafted. By grafting hydrophobic polymer chains onto hydrophobic polymers in place of low-molecular-weight hydrophobic groups, more stable nanogels with relatively large hydrophobic domains have been obtained. Here, we summarize our recent progress in the development of functional nanogels, formed by new associating copolymers grafted with polyelectrolytes for polyion complex formation or with polymers responsive to pH, temperature and redox potential.

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In this work, a three-armed coiled-coil peptide (TCP) was newly designed and synthesized as a building unit for self-assembly. Self-assembling properties of TCP in water were characterized by using CD, AFM, TEM and SEM analyses. The TCP was found to form coiled-coil structures at pH 5.8 and to self-assemble into nanofiber structures. The diameter of the nanofibers was well consistent with the theoretical diameter of a coiled-coil trimer structure. The high-order structure of TCP changed by varying the TFE (Trifluoroethanol) content in water, and as a result, vesicle-like aggregates were found to form in water/TFE (8/2 (v/v)) mixed solution. Thus, the secondary and self-assembled structures of TCP can be controlled by manipulating the pH and solution composition. These findings should provide useful information for developing novel peptide-based materials with well-defined nanostructures.

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Supramolecular chemistry is concerned with interactions between molecules, how they can recognize each other, assemble and function on a molecular scale. It provides a bottom up approach to nanoscale systems with applications ranging from biology to materials science. Merging of nanoparticles or nanotechnology, in a wide sense, with self-assembled systems such as liquid crystal displays (LCDs), may attract the attention of researchers who are interested in inaugurating new combinations of different fields. This study aims to synthesize supramolecule-stabilized rhodium nanoparticles and using them to develop novel display materials. Crown ether-stabilized rhodium nanoparticles and calixarene-stabilized rhodium (CA-Rh) nanoparticles have an average diameter of a single nanometer. The power consumption of this TN-LCDs in the presence of CA-Rh rhodium nanoparticles was low. The contrast ratio in the presence of CA-Rh nanoparticles is much better than that in the absence.

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In this study, complex formation of an amphiphilic cyclic compound, calix[4]resorcinarene (CR) with amines are reported. CR with 4 alkyl chains of 10 carbon atoms (CR(10)) were prepared by condensation of resorcinol and undecanal under acidic condition. CR(10) formed complexes with amines in ethanol. The complex formation is facilitated by hydrogen bonds between hydroxyl groups and amino groups. The complexes showed different thermal stability depending on the kind of amines. The complex obtained from CR(10) and diamines retained the structure in the molten state and until decomposition of CR(10). However, the complex obtained from CR(10) and monoamines decomposed to CR(10) and monoamines before the melting point of the complex. The thermal stability of the complexes depends on the number of amino groups that interact.

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Water-soluble polymer micelles which can incorporate guest molecules and release them in response to external stimuli can be used as drug delivery systems (DDS). In this study, temperature-responsive diblock copolymers composed of a block that contains pendant phosphorylcholine groups (PMPC) and a thermo-responsive poly(N,N-diethylacrylamide) (PDEA) block were prepared via controlled radical polymerization. PMPC dissolves in water independent of temperature and thus it is difficult for the immune system to recognize it as a foreign substance. Above the critical aggregation temperature (CAT), the diblock copolymers form polymer micelles composed of a hydrophobic PDEA core and a hydrophilic and biocompatible PMPC shell. Below the CAT, the polymer micelles dissociate, because the PDEA block becomes hydrophilic. Above the CAT the polymer micelles can incorporate hydrophobic guest molecules into the PDEA core. On the other hand, below the CAT these guest molecules are released into the bulk water phase from the micelles.

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Copper is easily oxidized in air to form copper oxides on the surface which is often problematic for applications, because this reduce the electrical conductivity. Here, we studied influence of coating of copper plates and fine particles with organic thiol compounds on oxidation resistance and electrical conductivity. Copper surfaces were coated with thiol terminated polystyrenes (PSt-SH)s by dipping copper in a solution of the thiol compound. XPS measurements revealed that the molecular thin layer of PSt-SH lead to a resistance against oxidation. Coating with 1-dodecanethiol (Dod-SH) was also effective. However, only the PSt-SH layer kept the oxidation resistance against heating at 150°C, which was confirmed by the color change by heating. The temperature dependences of the contact electrical resistance measured by the four-point method indicated that the electrical conductivity was hardly reduced for the surface coated with PSt-SH even at 150°C.

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The photopolymerization of a methacrylate compound by a photoinitiator system consisting of an iron arene complex and a sensitizing dye was investigated. Infrared absorption spectroscopy clarified that the photopolymerization did not proceed completely. Electron Spin Resonance measurements showed that a cyclopentadienyl radical (CPR) is generated by the photoreaction in this system. The amount of the propagating polymethacrylate radicals (PPR) generated during light irradiation by this system increased much less than that by the photoinitiator system consisting of a peroxide initiator and a sensitizing dye. Adding a phenylglycine compound (PC) reduced the amount of CPR, and increased that of PPR. These phenomena can be explained by (1) the inhibition of polymerization by CPR, and (2) the reduction of CPR by PC. Oxidized PC is assumed to generate an additional polymerization initiator, anilinomethyl radical. Addition of PC is an effective way to increase the polymerization degree of the photopolymer which uses this photoinitiator system.

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To synthesize crosslinked poly(n-butyl vinyl ether) [poly(NBVE)] with imine group linkages, α, ω-formylated poly(NBVE) was prepared by living cationic polymerization of NBVE using a bifunctional initiator (1) and water as terminator (M_n = 14,500，M_w/M_n = 1.29，F_n；1.91). Crosslinked poly(NBVE) was prepared by a crosslinking reaction of the formylated poly(NBVE) with tris(2-aminoethyl)amine. Although the original formylated poly(NBVE) was a sticky liquid, the obtained crosslinked poly(NBVE) was a gel and exhibited self-membrane-forming. The GPC curves of the soluble parts of crosslinked polymers clearly shifted to a higher-molecular-weight region and became broader [M_n = 34,800 (peak top), M_w/M_n = 7.59]. Also, crosslinked poly(NBVE) exhibited elasticity [elongation at break (E_b) = 186%，tensile strength (at break) (T_b) = 0.13 MPa]. A degradation reaction was carried out with an excess amount of phenylethylamine. The GPC curve of the obtained polymer shifted to a low-molecular-weight region (M_n = 14,100，M_w/M_n = 1.26).

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Conducting composite films of polyaniline/poly(acrylic acid) were prepared by electrochemical polymerization of aniline in the presence of poly(acrylic acid). An enzyme electrode was fabricated with the composite film by covalently immobilizing protocatechuate 3,4-dioxygenase on its surface. Amperometric sensing of protocatechuic acid (PCA) was carried out with the enzyme electrode by monitoring O₂ consumption accompanying enzymatic PCA oxidation. The sensing was conducted at an applied potential of −0.3 V vs. SCE in a phosphate buffer solution at pH 7.0. The current response was found to increase linearly with an increase in PCA concentration up to 0.55 mM. The sensitivity was 155 µA mM⁻¹ cm⁻² with the detection limit of 5 µM. The enzyme electrode gave no response to phenolic compounds other than PCA and to electroactive species such as ascorbic acid and acetaminophen. This high selectivity can be attributed to the substrate specificity of protocatechuate 3,4-dioxygenase and the low potential for amperometry.

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