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Helical Polymer (helical + polymer)
Selected AbstractsPhotoinduced Racemization of an Optically Active Helical Polymer Formed by the Asymmetric Polymerization of 2,7-Bis(4- tert -butylphenyl)fluoren-9-yl Acrylate,ANGEWANDTE CHEMIE, Issue 49 2009Takeshi Sakamoto Dr. Ein Lichttrick: Ein durch asymmetrische anionische Polymerisation hergestelltes optisch aktives helicales Polymer mit Vorzugshändigkeit ging bei Photobestrahlung eine Stereomutation ein. Dagegen blieb die Helix beim Erhitzen stabil (siehe Bild). Diese photoinduzierte Racemisierung eines synthetischen helicalen Polymers verlief ohne Änderung der chemischen Bindung wie Bindungsbildung, Bindungsspaltung oder Isomerisierung einer Doppelbindung. [source] Poly(thiaheterohelicene): A Stiff Conjugated Helical Polymer Comprised of Fused Benzothiophene Rings.CHEMINFORM, Issue 24 2005Tomokazu Iwasaki No abstract is available for this article. [source] Synthesis, Characterization, and Folding Behavior of ,-Amino Acid Derived PolyisocyanidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2006Sander J. Wezenberg Abstract Helical polymers of isocyanopeptides derived from ,-amino acids have been synthesized and their architectures have been studied in detail. Similar to their ,-amino acid analogues, the helical conformation in these macromolecules is stabilized by internal hydrogen-bonding arrays along the polymeric backbone. Unexpectedly, the flexibility of the ,-peptide side arms results in a rearrangement of the initial macromolecular architecture, leading to a more stable helical structure possessing a better defined hydrogen-bonding pattern, as was concluded from IR and temperature-dependent circular dichroism studies. Based on these results we propose a dynamic helical model for the ,-amino acid derived polyisocyanopeptides; this model is in contrast to the kinetically stable helical macromolecules that are formed upon polymerization of ,-amino acid based isocyanopeptides. [source] Solvent-Induced Self-Assembly of a Meta -Linked Conjugated Polyelectrolyte.ADVANCED MATERIALS, Issue 14 2004Amplified Quenching, Guest Intercalation, Helix Formation A water-soluble meta -linked poly(phenylene ethynylene) is shown to fold into a helical conformation in water. The helix is stabilized by solvophobic forces and ,-stacking interactions. The metallo-intercalator complex Ru(dppz)(phen)22+ binds to the helical polymer via intercalation and the complex is highly luminescent when it is bound to the polymer (see Figure). [source] Stability of poly(N -propargylamide)s under ultraviolet irradiationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Jianping Deng Abstract This article investigates the photostability of poly(N -propargylamide)s under different conditions, on the basis of which application research for this class of highly functional polymers can be performed. With helical polymer 1 [monomer: CCCH2NHCOCH(C2H5)2] taken as a representative, some affecting factors, including the ultraviolet (UV)-light intensity, presence of oxygen, far-UV and near-UV light, and temperature, were investigated. It was found that increasing the UV-light intensity accelerated the degradation of polymer 1. When oxygen was present, it also facilitated the degradation. Far-UV light rather than near-UV light played a predominant role in initiating the degradation of polymer main chains. Elevating the temperature of the polymer solution during UV irradiation made the degradation accelerate. Storing the polymer under weak UV light, in the absence of oxygen, and at a low temperature was favorable for keeping the polymer stable. These findings are important not only from a scientific point of view but especially for developing practical applications of this type of polymer on the basis of its photodegradability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Chiral polymers for resolution of enantiomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2009Yoshio Okamoto Abstract In 1979, the formation of one-handed helical poly(triphenylmethyl methacrylate) (PTrMA) was found through the helix-sense-selective polymerization of methacrylate using chiral anionic initiators, and the existence of a stable helical polymer without chiral side chains was proved. The chiral polymer exhibited unexpected high chiral recognition of various racemic compounds when used as the chiral packing material (CPM) for HPLC, which was commercialized in 1982 as the first chiral column based on an optically active polymer. This success encouraged us to develop further useful commercial chiral packing materials (CPMs) based on polysaccharides, cellulose, and amylose. By using these polysaccharide-based CPMs, particularly phenylcarbamate derivatives, nearly 90% of chiral compounds can be resolved not only analytically but also preparatively, and several chiral drugs have been produced using the CPMs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1731,1739, 2009 [source] Development of synthetic double helical polymers and oligomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Yoshio Furusho Abstract There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical counterparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5195,5207, 2009 [source] Molecular design and synthesis of artificial double helicesTHE CHEMICAL RECORD, Issue 1 2007Yoshio Furusho Abstract This account describes novel artificial double helices recently developed by our group. We have designed and synthesized the double helices consisting of two complementary, m -terphenyl-based strands that are intertwined through chiral amidinium,carboxylate salt bridges. Due to the chiral substituents on the amidine groups, the double helices adopted an excess one-handed helical conformation in solution as well as in the solid state. By extending the modular strategy, we have synthesized double helices bearing Pt(II) linkers, which underwent the double helix-to-double helix transformations through the chemical reactions of the Pt(II) complex moieties. In addition, artificial double-stranded metallosupramolecular helical polymers were constructed by combining the salt bridges and metal coordination. In contrast to the design-oriented double helices based on salt bridges, we have serendipitously developed a spiroborate-based double helicate bearing oligophenol strands. The optical resolution of the helicate was successfully attained by a diastereomeric salt formation. We have also unexpectedly found that oligoresorcinols consisting of a very simple repeating unit self-assemble into double helices with the aid of aromatic interactions in water. Furthermore, a bias in the twist sense of the double helices can be achieved by incorporating chiral substituents at both ends of the strands. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 1,11; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20097 [source] | |||||||||||||