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41.
Kazuhiro Marumo Manabu Itoh Sungmin Kang Koichi Sakajiri Junji Watanabe 《Liquid crystals》2013,40(2):234-238
Galactose derivatives were explored as chiral dopants, effective for inducing chiral nematic liquid crystal (LC) phases. Galactose bearing O-isopropylidene substituents at the C3 and C4 and butoxybiphenyl substituents at the C2 and C6 positions exhibits a high helical twisting power (HTP) value of ?74.4 μm?1. Such a high HTP value for the galactose derivative is attributed to (1) linkage of the C3 and C4 carbons with the O-isopropylidene substituent, which places the C2 and C6 substitutes in a skew arrangement at a large angle and (2) enhancement of the affinity with the host nematic LCs by incorporating aromatic substituents at the C2 and C6 positions that are similar to those in the host. 相似文献
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Mechanism of Macroscopic Motion of Oleate Helical Assemblies: Cooperative Deprotonation of Carboxyl Groups Triggered by Photoisomerization of Azobenzene Derivatives 下载免费PDF全文
Dr. Yoshiyuki Kageyama Tomonori Ikegami Yuta Kurokome Prof. Dr. Sadamu Takeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8669-8675
Macroscopic and spatially ordered motions of self‐assemblies composed of oleic acid and a small amount of an azobenzene derivative, induced by azobenzene photoisomerization, was previously reported. However, the mechanism of the generation of submillimeter‐scale motions by the nanosized structural transition of azobenzene was not clarified. Herein, an underlying mechanism of the motions is proposed in which deprotonation of carboxyl groups in cooperation with azobenzene photoisomerization causes a morphological transition of the self‐assembly, which in turn results in macroscopic forceful dynamics. The photoinduced deprotonation was investigated by potentiometric pH titration and FTIR spectroscopy. The concept of hierarchical molecular interaction generating macroscale function is expected to promote the next stage of supramolecular chemistry. 相似文献
44.
Bhanu P. Mudraboyina Prof. James A. Wisner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(44):14157-14164
The design and syntheses of four self‐complementary oligomers that contain an underlying AADD hydrogen bond sequence are presented, and their self‐association was examined in the solution and solid state. The molecular recognition between the two strands is highly sensitive to substitutions of their component heterocycles. Substitution with electron‐donating and ‐withdrawing groups and the influence of preorganization has a large effect on the overall stabilities of the complexes studied. In particular, a wide range (>105 M ?1) of stabilities with respect to substitutions at various positions in the AADD oligomers was demonstrated. In the most extreme case, the dimerization constant measured (Kdimer≥4.5×107 M ?1) is comparable to the most stable homodimers of neutral AADD arrays reported to date. 相似文献
45.
Structure‐guided RP‐HPLC chromatography of diastereomeric α‐helical peptide analogs substituted with single amino acid stereoisomers 下载免费PDF全文
YiBing Huang Ling Pan LianJing Zhao Colin T. Mant Robert S. Hodges Yuxin Chen 《Biomedical chromatography : BMC》2014,28(4):511-517
An α‐helical model peptide (Ac‐EAEKAAKE‐X‐EKAAKEAEK‐amide) was used as a template to examine the efficacy of conventional reversed‐phase high‐performance liquid chromatography (RP‐HPLC) in separating peptide analogs with single substitutions (at position X) of diasteromeric amino acids Ile, allo‐Ile, d ‐Ile and d ‐allo‐Ile. We compared differences in peptide retention behavior on a C8 column and a C18 column at different temperatures. We demonstrated how subtle differences in peptide secondary structure affected by the different substitutions of amino acids with identical overall hydrophobicity enabled effective resolution of these peptide analogs. We also demonstrated the ability of RP‐HPLC to separate Ile‐ and allo‐Ile‐substituted analogs of a 26‐residue α‐helical antimicrobial peptide (AMP), with the substitution site towards the C‐terminus of the α‐helix. These peptides show different values of antibacterial activity and hemolytic activity, and different selectivity against bacteria and human cells. Our results underline the ability of RP‐HPLC to resolve even difficult diasteromeric peptide mixtures as well as its value in monitoring very subtle hydrophobicity changes in de novo‐designed AMP. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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A method for measuring the spontaneous polarization P s, the switching time, the rotational viscosity γφ, and the d.c. conductivity σ is presented. The possibilities of estimating the azimuthal angle φ0, the dielectric anisotropy δε and the dielectric permittivity ε⊥ in the same experiment are also discussed. It is explicitly shown that the switching delay, though primarily dependent on the material and the applied field, is also dependent on the geometry of the cell. 相似文献
48.
Hong Xia Yoshio Hashimoto Toru Morita Toshihiro Hirai 《Journal of Polymer Science.Polymer Physics》2014,52(13):887-892
Few solvents are capable of dissolving polyketones (PKs). 1,1,1,3,3,3‐Hexafluoro‐2‐propanol (hexafluoroisopropanol, HFIP) is a better solvent than trifluoroethanol and m‐cresol. When HFIP was evaporated from a PK/HFIP solution, a porous cast‐film with a microparticle structure was formed because the isotactic PKs adopted a helical conformation, and convection during evaporation of the high polarity and low‐boiling‐point HFIP caused aggregation and rolling of the polymer molecules. The addition of plasticizer suppressed particle formation, improving the surface structure and mechanical properties of the film. In particular, the dielectric properties of the film improved significantly. This will enable PKs, which are rigid insulating materials, to be used as dielectric materials, broadening their range of applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 887–892 相似文献
49.
Yoshio Aso Shoji Nishiguchi Tetsuya Jigami Tetsuo Otsubo Fumio Ogura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):417-418
Several well-defined 3,4-thienylene-ethynylene oligomers with different chain lengths have been synthesized and characterized. X-Ray crystallographic analyses proved their unique, totally helical conformations. 相似文献
50.
Nimmy R. Mammoottil James F. Reuther Dumindika A. Siriwardane Oleg V. Kulikov Bruce M. Novak 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2915-2934
Described herein is a comprehensive survey on the most recent advancements in polycarbodiimide synthetic methodologies, structure determination, property design, and self-assembly. In particular, the 15N-isotopic enrichment of polycarbodiimides is detailed along with the use of 15N NMR to identify the regioregularity and mechanism of chiroptical switching in polycarbodiimides. Furthermore, the new Ni(II) mediated “living” polymerization is explained along with its utilization in the incorporation of polycarbodiimides into block copolymers, graft copolymers, and star polymers. Finally, we review the recent discoveries focusing on the highly tunable self-assembly behaviors of polycarbodiimide homopolymers and copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2915–2934 相似文献