Summary: The phase behavior and optical properties of a cholesteric ternary copolymer, containing nematogenic phenylbenzoate, cholesteric, and photochromic diarylethene side groups, and its mixture with 2 wt.‐% fluorescent dopant were studied. The investigation of the kinetics of a photochemical opening‐cycle process of the photochromic groups in the cholesteric mixture proved the energy transfer from the fluorescent dopant to the photochromic diarylethene groups. It was shown that the fluorescence intensity of the fluorescent dopant could be controlled by the portion of the “closed” form of the diarylethene groups. During the photocyclization of the photochromic groups a “degeneration” of the selective light reflection of the cholesteric matrix is observed.Fluorescence‐resonance energy transfer makes possible the process of photosensitization of the back ring‐opening photoreaction of the photochromic diarylethene groups in the cholesteric polymer matrix.imageFluorescence‐resonance energy transfer makes possible the process of photosensitization of the back ring‐opening photoreaction of the photochromic diarylethene groups in the cholesteric polymer matrix.
The internal friction (e-'), ultrasonic attenuation ((U) and variation of Young's modulus (AEIE) of YBa2Cu309_, were measured with frequencies of 5 kHz, 120 kHz and 5 MHz. Several Q-' (or (U) peaks and corresponding minima of A E / E were observed.According to x-ray diffraction results, the Q-' peak as well as other anomalies can be attributed to a discontinuous change of lattice parameters. The tendency to elastic softening above 90 K may play an important role in superconductivity.
Novel 1,2-bis(2-alkylthien-3-yi)hexafluorocyclopentenes containing the alkylthio or alkylsulfonyl groups in positions 5 and 5' of the thiophene rings were synthesized. These compounds are photoehromes; their photochromic properties were studied.
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