Synthesis and polymerization of a novel perfluorinated monomer

Perfluoro(5-methylene-2,2-dimethyl-1,3-dioxolane) (1) was synthesized by utilizing a direct fluorination reaction. Compound 1 was an entirely novel monomer with difluoromethylene at position 5 on the dioxolane ring as an unprecedented polymerization site. It successfully polymerized with tetrafluoroethylene to afford copolymers, which had T_g values in the range of 60-90 °C. The content of monomer 1 in the obtained polymers was less than 20 mol%, which seemed insufficient for giving various unique properties to polymers. However, each polymer was expected to be a superior material because of their advanced thermal stability. Comparison with copolymers of 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole and tetrafluoroethylene is also discussed.     

Spin crossover phenomenon accompanying order-disorder phase transition in the ligand of [FeII(DAPP)(abpt)](ClO4)2 compound (DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) and its successive self-grinding effect

The spin crossover phenomenon of the recently described spin crossover complex [FeII(DAPP)(abpt)](ClO4)2 [DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] accompanying an order-disorder phase transition of the ligand was investigated by adiabatic heat capacity calorimetry, far-IR, IR, and Raman spectroscopies, and normal vibrational mode calculation. A large heat capacity peak due to the spin crossover transition was observed at T(trs) = 185.61 K. The transition enthalpy and entropy amounted to Delta(trs)H = 15.44 kJ mol-1 and Delta(trs)S = 83.74 J K-1 mol-1, respectively. The transition entropy is larger than the expected value 60.66 J K-1 mol-1, which is contributed from the spin multiplicity (R ln 5; R: the gas constant), disordering of the carbon atom of the six-membered metallocycle in the DAPP ligand, and one of the two perchlorate anions (2R ln 2), and change of the normal vibrational modes between the high-spin (HS) and low-spin (LS) states (35.75 J K-1 mol-1). The remaining entropy would be ascribed to changes of the lattice vibrations and molecular librations between the HS and LS states. Furthermore, [Fe(DAPP)(abpt)](ClO4)2 crystals disintegrated and became smaller crystallites whenever they experienced the phase transition. This may be regarded as a successive self-grinding effect, evidenced by adiabatic calorimetry, DSC, magnetic susceptibility, and microscope observation. The relationship between the crystal size and the physical quantities is discussed.     

Self-assembled plasmid DNA network prepared through both triple-helix formation and streptavidin–biotin interaction

Plasmid DNA responds to external stimuli to change the degree of supercoiling. As a result of its unique topological change, plasmid DNA is considered to be a new functional material. In addition to its stimuli-responsiveness, plasmid DNA has the capability of forming a triple helix with a triple-helix-forming oligonucleotide (TFO). The triple helix is formed in aqueous conditions and arises through recognition of specific sequences, and may lead to the formation of supramolecular architectures. With this in mind, we analyze the self-assembly of recombinant plasmid DNA with two sequences for triple-helix formation and TFO by means of surface plasmon resonance. In addition, the network formed by self-assembly of the recombinant plasmid DNA with biotinated-TFO and streptavidin is prepared and evaluated by atomic force microscopy (AFM).

Schematic illustration of plasmid DNA network.     

Effect on bending behavior of counter cation species in perfluorinated sulfonate membrane–platinum composite

The perfluorinated sulfonate membrane (Nafion ®117)–platinum composites having H⁺, mono- and bivalent metal ions as counter cations in the membranes were prepared and the bending behaviors of the composites actuated by the step voltage were investigated in deionized water. The bending behaviors of all composites have the same tendency as the composites to bend quickly to the anode side just after applying the step voltage and gradually to bend back to the cathode side in spite of keeping on the application. However, they show differences in the bending rate and the maximum displacement to the anode side just after applying the step voltage, which are influenced by counter cation species in the membrane. In particular, the composite having Li⁺ has the largest maximum displacement (about 1.1 mm) to the anode side. The relationship between the maximum displacements of the composites and water states in the membranes were studied. The maximum displacements of the composites depend on the water content in the membranes. In both series of the composites having mono- and bivalent metal ions, the maximum displacements increase with increasing water content, except the composites having Rb⁺ and Sr²⁺ which belong to fifth period in the periodic table. In spite of the result that the water content in the membrane having H⁺, which is about 20wt%, is nearly equal to that in the membrane having Na^a, the maximum displacement of the composite having H⁺ is only about one-third as large as that of the composite having Na⁺. The water structures in the membranes were investigated by using differential scanning calorimetry (DSC). The DSC endothermograms obtained indicate that the freezing water in the membrane having H⁺ has a much stronger interaction with sulfonate groups and counter cations than that in the membrane having Na⁺. It is concluded that the content and structure of the freezing water in the membrane have a profound effect on the bending behavior of the composite. © 1998 John Wiley & Sons, Ltd.     

Synthesis of cancer peptide antigen-lipid A analog conjugates for synthetic vaccines.

Conjugates 6 and 7 of cancer peptide antigen with N-tetradecanoyl L-serine-beta-alanine-containing D-glucosamine derivative structurally related to lipid A as an immunoadjuvant were synthesized for the development of totally synthetic vaccines against cancers. The mitogenic activities of compounds 6 and 7 were stronger than that of lipid A analog 3.     

Enzymatic Degradation of Semi‐IPN Hydrogels Based on N‐Isopropylacrylamide and Dextran at a Specific Temperature Range

The temperature‐dependent enzymatic degradation of semi‐IPN hydrogels consisting of dextran grafted with thermo‐responsive chains (lower cloud point) and a thermo‐responsive crosslinked matrix (higher cloud point) was examined. Enzymatic degradation of the semi‐IPN hydrogel was significantly inhibited below the lower and above the higher cloud point. Only between both cloud points, enzymatic degradation proceeded. The designed semi‐IPN hydrogel is therefore advantageous to achieve enzymatic degradation at a specific temperature range.     

Phosphorus-containing hybrid calixphyrins: promising mixed-donor ligands for visible and efficient palladium catalysts

Phosphorus-sulfur-containing hybrid calixphyrins were prepared by the BF3-promoted dehydrative condensation between sigma4-2,5-bis[(pyrrol-2-yl)methyl]phosphole and 2,5-bis[hydroxy(phenyl)methyl]thiophene. X-ray crystallographic analysis of the Pd-P,N2,S-hybrid calixphyrin complex revealed that the Pd center was coordinated by the four heteroatoms to adopt a distorted square planar geometry. The Pd complex, displaying a characteristic reddish purple color in solution, catalyzed the Heck reaction of bromoarenes with n-butyl acrylate with high efficiency at elevated temperatures.     

Dendritic nanospace constructed by only glycerol units enhanced uptake of a fluorescent molecule in aqueous solution

A polyglycerol dendrimer (PGD) of generation 2, which consists of only glycerol units, constructed nanospace capable of uptake of a fluorescent molecule with a 1:1 stoichiometry. On the other hand, a PGD of generation 1 trapped the molecule at the outer part.