Symmetrically substituted poly(diphenylacetylene)s bearing optically active 2-octyloxycarbonyl groups at the -positions of the pendant phenyl rings not only show a unique solvent-dependent helix inversion to afford diastereomeric right- and left-handed helical polymers but also significant unprecedented solvent-dependent changes in the helix inversion barrier of the polymer backbone resulting in switching between static or dynamic behavior of the helical polymers at approximately room temperature depending on the solvents used.
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http://dx.doi.org/10.1039/d4cc02656j | DOI Listing |
Chemistry
November 2024
University of Warsaw: Uniwersytet Warszawski, Faculty of Chemistry, ul. Pasteura 1, Warsaw, POLAND.
Light Sci Appl
September 2024
Advanced Laser Technology Laboratory of Anhui Province, Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei, Anhui, China.
Single-particle tracking (SPT) is an immensely valuable technique for studying a variety of processes in the life sciences and physics. It can help researchers better understand the positions, paths, and interactions of single objects in systems that are highly dynamic or require imaging over an extended time. Here, we propose an all-dielectric one-dimensional photonic crystal (1D PC) that enhances spin-to-orbital angular momentum conversion for three-dimensional (3D) SPTs.
View Article and Find Full Text PDFACS Photonics
September 2024
ETH Zurich, Department of Physics, Institute for Quantum Electronics, Optical Nanomaterial Group, 8093 Zurich, Switzerland.
Second-harmonic generation (SHG) is prohibited in centrosymmetric crystals such as silicon or germanium due to the presence of inversion symmetry. However, the structuring of such materials makes it possible to break the inversion symmetry, thus achieving generation of second-harmonic. Moreover, various symmetry properties of the resulting structure, such as chirality, also influence the SHG.
View Article and Find Full Text PDFMacromol Rapid Commun
November 2024
Clemens-Schöpf-Institute for Organic Chemistry and Biochemistry, Technical University of Darmstadt, Peter-Grünberg-Straße 16, 64287, Darmstadt, Germany.
Many polypeptides form stable, helical secondary structures enabling the formation of lyotropic liquid crystalline (LLC) phases. Contrary to the well-studied polyglutamate, their counterparts based on polyaspartates exhibit a much lower helix inversion barrier. Therefore, the helix sense is not solely dictated by the chirality of the amino acid used, but additionally by the nature and conformation of the polymer sidechain.
View Article and Find Full Text PDFJ Chem Phys
August 2024
School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
Unidirectional photochemical molecular motors can act as a power source for molecular machines. The motors operate by successive excited state isomerization and ground state helix inversion reactions, attaining unidirectionality from an interplay of steric strain and stereochemistry. Optimizing the yield of the excited state isomerization reaction is an important goal that requires detailed knowledge of excited state dynamics.
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