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61.
Shuai Liu Xiaomeng Liu Sangen Zhao Youchao Liu Lina Li Qingran Ding Yanqiang Li Zheshuai Lin Junhua Luo Maochun Hong 《Angewandte Chemie (International ed. in English)》2020,59(24):9414-9417
Birefringent materials, which can modulate the polarization of light, are almost exclusively limited to oxides. Peroxides have long been overlooked as birefringent materials, because they are usually not stable in air. Now, the first peroxide birefringent material Rb2VO(O2)2F is reported, the single crystals of which keep transparency after being exposed in the air for two weeks. Interestingly, Rb2VO(O2)2F does not feature an optimal anisotropic structure, but its birefringence (Δn=0.189 at 546 nm) exceeds those of the majority of oxides. According to the first‐principles calculations, this exceptional birefringence should be attributed to the strong electronic interactions between localized π orbital of O22? anions and V5+ 3d orbitals, which may be also favorable to the stability in the air for Rb2VO(O2)2F. These findings distinguish peroxides as a brand‐new class of birefringent materials that may possess birefringence superior to the traditional oxides. 相似文献
62.
Yuki Arakawa Hiroki Kuwahara Masatoshi Tokita Gen-ichi Konishi Hideto Tsuji 《Molecular Crystals and Liquid Crystals》2018,662(1):197-207
ABSTRACTWe present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242. 相似文献
63.
作为一种有可能作为永久信息存储的材料,合成出一种新的双偶氮材料(BA1)。当样品被波长为532nm的光激发时,几乎大部分BA1分子从反-反态转化到顺-顺态,产生了光致双折射。因此,研究了BA1分子掺杂的PMMA薄膜的光致双折射和透过信号与入射光强度的关系。实验结果表明:透过信号强度随着泵浦光的增强而增强。通过偏振态互相平行(SS)和垂直(SP)的两束偏振光用来研究偏振全息存储,结果表明SP光栅形成的衍射信号要比SS光栅的衍射信号强很多。 相似文献
64.
3,5-二氰基-2,4,6-三甲基吡啶在新型光电功能材料的合成中有重要的应用价值.本文在CCl4中光照1,4-二氢-3,5-二氰基-2,4,6-三甲基吡啶,高产率地合成了3,5-二氰基-2,4,6-三甲基吡啶. 相似文献
65.
Pierluigi Perrone Silvello Betti Giuseppe Giulio Rutigliano 《Fiber and Integrated Optics》2017,36(4-5):181-195
This article proposes a novel coherent multilevel modulation model that exploits polarization and phase of the field. This model is based on the possibility of coherent systems to use all the four degrees of freedom of the electromagnetic field. The proposed scheme is able, by applying a suitable twisting process to the optical fiber, to physically confine the polarization and the phase of the transmitted field within the phase sphere. In this way, with the same performances of existing systems, the receiver is considerably simplified because there is no longer need of birefringence tracking circuits. 相似文献
66.
An experimental method has been developed for determining the mechanism of luminescence of crystals by the changes arising in the intensity of a burst of their luminescence under the action of a constant electric field. An example of determining the mechanism of luminescence of AgBr crystals and AgBr0.95 and AgBr0.60Cl0.40 solid solutions by the method proposed is presented. We were the first to establish that the low-temperature photoluminescence of AgBr0.95I0.05 in the band with max = 540 nm proceeds by the Schone–Klasens recombination mechanism. It has also been established that the longwave luminescence of AgBr, AgBr0.95I0.05, and AgBr0.60Cl0.40 in the band with max = 630 nm arises as a result of the recombination of electrons localized on a luminescence center with free holes. 相似文献
67.
Intermolecular photoinduced electron transfer (PET) in a gas phase was studied using carbazole vapor fluorescence quenching by halomethanes (CHCl3, CH2Br2, CCl4, CHBr3). The fluorescence quenching rate constants k
q changing from 2.3·105 sec–1·torr–1 in mixtures with CHCl3 to 4.6·106 sec–1·torr–1 in mixtures with CHBr3 at a constant temperature of 403 K were estimated. The dependence of the carbazole fluorescence decay rates in the presence of halomethanes on the free energy change G during transfer of the electron from carbazole to halomethanes is considered. It is suggested to take into account the influence of the vibrational energy of the carbazole molecule E
vib and its temperature changes in estimation of the G values. The differences between PET in the gas and liquid phases were analyzed. It is found that for mixtures with CCl4 and CHBr3 the negative temperature dependence of k
q is observed, when the decay rates and efficiencies of the intermolecular PET decreased with temperature increase in the range 403–573 K, i.e. these mixtures the electron transfer is not a barrier-restricted process. 相似文献
68.
S. B. Bushuk W. E. Douglas Ju. A. Kalvinkovskaya L. G. Klapshina A. N. Rubinov B. A. Bushuk A. P. Stupak 《Journal of fluorescence》2003,13(4):331-338
The spectroscopic characteristics of novel -conjugated polymers containing four-coordinated silicon, acetylene groups and either 1,4-biphenylene or 2,7-fluorene in the main chain were investigated by steady-state and picosecond laser spectroscopy. The spectral features of absorption, fluorescence excitation spectra, fluorescence lifetime, and fluorescence polarization were explained by the existence of two kinds of inhomogeneously broadened electronic states formed in the disordered polymeric chain. The dynamics of photoinduced absorption was measured in the 400–900 nm spectral range with picosecond time resolution. The long-wavelength band with max 710 nm was ascribed to excited-state absorption from higher-lying electronic states created in short polymeric segments with essential conformational distortion of the subunits. The short-wavelength band with max 580 nm and a shoulder at 500 nm was interpreted as photoinduced absorption from a lower-lying state arisen in more planar, longer -conjugated segments populated via direct excitation and energy migration between disordered segments of the polymeric chain. For the fluorene-containing polymer, the smaller Stokes shift and the greater degree of fluorescence polarization are consistent with more extensive electron delocalization along the backbone. 相似文献
69.
Although fiber spinning is known to reduce polarization mode dispersion (PMD) effects in optical fibers, relatively few studies
have been performed of the dependence of the reduction factor on the strength of random birefringence fluctuations. In this
paper, we apply a general mathematical model of random fiber birefringence to sinusoidally spun fibers. We find that while
even in the presence of random birefringence perturbations the maximum reduction of PMD is still obtained when the phase matching
condition is satisfied, the degree of PMD reduction and the probability distribution function of the DGD both vary with the
random birefringence profiles. 相似文献
70.
Binnur Aydogan Temel Julia Amici Marco Sangermano Yusuf Yagci 《Journal of polymer science. Part A, Polymer chemistry》2013,51(21):4601-4607
Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD‐type H‐shaped complex copolymer. First, α‐benzophenone functional polystyrene (BP‐PS) and poly(methyl methacrylate) (BP‐PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene‐b‐poly(methyl methacrylate) (PS‐b‐PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of ε‐caprolactone (CL) by using PS‐b‐PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL‐PS‐PMMA‐PCL. Finally, the polymerization of tert‐butyl acrylate (tBA) via iniferter process gave the targeted H‐shaped block copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4601–4607 相似文献