Fluorinated surfactants: synthesis properties applications,by Erik Kissa. Marcel Dekker Inc., New York, 1994, pp. vii + 469, price US$165.00. ISBN 0-8247-9011-1

The photocoloration of a novel spirooxazine, 1-[β-(4-trifluoromethyl benzoyloxy)ethyl]-3,3-dimethyl-spiro[indoline-2,3′-[3H]-naphtho[2,1-b]-1,4-oxazine] (SO), doped in different polymer films and fibers was studied. The results show that photocoloration increased with increasing concentration of spirooxazine in polymer films. The photocoloration rate of spirooxazine in PMMA is faster than that in PS due to the polarity of the polymer films. A general model for the kinetics of photocoloration of spirooxazine in polymer films is proposed. The results also show that the photocoloration rate of spirooxazine in PET is faster than that in Nylon-6 due to the crystallinity of the polymer fibers.     

Structure dependence of photochromism of azobenzene‐functionalized polythiophene derivatives

Two novel azobenzene‐functionalized polythiophene derivatives, poly[4‐((4‐(phenyl)azo)phenoxy)butyl‐3‐thienylacetate] (PATh‐4) and the copolymer of 3‐hexylthiophene and 4‐((4‐(phenyl)azo)phenoxy)butyl‐3‐thienylacetate (COP‐64) were synthesized. The structure and photoelectronic behavior of both polythiophene derivatives were characterized by NMR, FTIR, UV–vis, XRD, GPC, modulated DSC, and photoluminescence spectroscopy. These new polymers combine photoluminescence property and photochemical behavior of both polythiophene‐conjugated backbones and the photoisomerizable moieties in the side chains. The photoluminescence property of polymers so obtained can be modified reversibly through the photochemical isomerization reaction of the photoactive groups in side chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation of luminescent polyethylene plastic composite nano-reinforced with glass fibers

Electrospun glass nanofibers (EGNFs) were prepared to reinforce polyethylene (PE) plastic waste towards the development of photochromic anti-counterfeiting patterns and long-persistent photoluminescent materials, such as smart windows and concrete. By physical integration of lanthanide-doped aluminate (LdA) nanoparticles (NPs) into polyethylene plastic reinforced with EGNFs, a transparent lanthanide-doped aluminate nanoparticles (LdANPs)/EGNFs@PE sheet was produced. The colorless EGNFs@PE hybrids became green under ultraviolet (UV) rays and greenish-yellow in a darkened room as proved by CIE Lab and photoluminescence analysis. In the luminescent LdANPs/EGNFs@PE hybrids, the identified photochromism was promptly reversed at low concentrations of LdANPs to designate fluorescence emission. Photoluminescence was maintained with slow reversibility for the high phosphor concentrations to designate afterglow emission. LdANPs exhibit diameters of 5–12 nm, whereas glass nanofibers have diameters of 70–120 nm. The morphologies of LdANPs/EGNFs@PE substrates were studied by energy-dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), and x-ray fluorescence (XRF). The mechanical properties of the prepared polyethylene plastic were enhanced by reinforcement with glass nanofibers as a roughening agent. The photoluminescent substrates showed markedly improved scratch resistance in comparison to LdANPs-free EGNFs@PE substrate. The obtained luminescence spectra displayed an emission band at 519 nm upon excitation at 365 nm. The results demonstrated that the luminous plastic has improved hydrophobicity and UV shielding upon increasing the LdANPs content.     

Delayed onset of photochromism in molybdenum oxide films caused by photoinduced defect formation

We report the photochromic properties of amorphous MoO₃ films deposited by dc sputtering with different O₂ flow rates. The kinetics of film coloration under UV light irradiation is determined using optical transmission spectroscopy. Changes in the absorbance and refractive index were derived from the analysis of transmittance spectra. The absorbance spectra exhibited a growing broad peak centered around 830 nm, which was induced by the UV irradiation. In the early stages of irradiation, the absorbance of the films did not change but their refractive indices did change. This induction time was correlated with the O₂ partial pressure during the film deposition, which was controlled by the O₂ flow rate. The origins of this observation are discussed.     

基于光控二芳基乙烯的手性向列相液晶体系研究进展

光控手性分子开关结合到液晶材料体系中,可以有效利用其光诱导的手性变化,实现远程光刺激液晶材料的自组装螺旋超结构。二芳基乙烯（DAE）是一类新型的、有前景的光致变色分子,作为智能光响应开关,在手性向列相液晶材料体系中表现出优异的性能。本文重点围绕结构设计,总结了一系列具备不同螺旋扭曲力（HTP）的手性DAE分子及其在液晶自组装螺旋结构中所产生的特定性能,如光可逆宽范围调控和光控手性反转。该类光控DAE手性向列相液晶体系在手性调控、光学显示、可调谐激光等领域具有巨大的应用潜力。最后讨论了该领域面临的挑战和机遇,并指出了未来可能的发展方向。     

Single-Component Photochromic Smart Semiconductor with Photoswitchable Fast Bidirectional Electron Transfer

Introduction of photochromic properties into semiconductors confers semiconductors with smart behaviors, color-related applications, and new modulation approaches. Photochromophores with electron-transfer (redox) behavior, such as viologen and naphthalene diimide, are ideal functional motifs to design photochromic semiconductors owing to good adaptability to the solid matrix, but their reverse reactions are exclusively realized by the thermal mode, which is slow (in dozens of seconds or longer) and thus significantly hinders real applications in the fields that require high-speed switching. This study reveals that photoexcitation in the electronic absorption band of the π-aggregate of viologen cation radicals can successfully trigger reverse electron transfer quickly (in 1 s with a continuous-wave 808 nm laser at a power density of 5 W cm⁻²; the photothermal effect is excluded), and the first single-component all-optically photochromic semiconductor is accordingly discovered. This discovery breaks through a traditional concept that reverse reactions of viologen compounds can not be triggered by the light, and provides a potential approach to realize all-optical switch of single-component photochromic smart semiconductors based on electron-transfer photochromic functional motifs.     

Light‐induced cooperative electron–proton transfer in hydrogen‐bonded networks of N,N‐diaryl substituted 1,4‐bisimines and meso‐1,2‐diaryl‐1,2‐ethanediols

The 1:1 cocrystallization of 1,4‐diaryl‐1,4‐bisimines (Ar–CHN–CH₂‐)₂ 4 – 11 and substituted meso‐1,2‐diaryl‐1,2‐ethanediols 1 – 3 leads to supramolecular structures in which the diol is hydrogen bonded by one of its hydroxy groups to an imine nitrogen atom of a 1,4‐bisimine. The second functionality in each molecule leads to the generation of ladderlike polymeric structures where each molecule of the diol is linked to two molecules of the 1,4‐bisimine and vice versa. If the diol carries electron donor groups in the aromatic residue and the 1,4‐bisimine correspondingly acceptor groups, then charge transfer interactions are observed. The excited CT complex which corresponds to a radical ion pair is stabilized by migration of a proton of a hydroxy group to the nitrogen atom of an imino group. This is supported by the appearance of a N–H vibration in the IR spectra. The reorganization is also accompanied by changes in the UV/Vis spectra and by the generation of paramagnetism in the crystalline material. The results represent a type of photochromism which has its origin in a light‐induced cooperative electron–proton transfer. The photochromism is thermally reversible.     

Light-Induced Electron Transfer Toward On/Off Room Temperature Phosphorescence in Two Photochromic Coordination Polymers

Photoswitchable room temperature phosphorescence (RTP) materials are of great interest due to their potential applications in optical devices and switches. Herein, two Zn-based coordination polymers (CPs) (H₃-TPB)·[Zn₆(H-HEDP)(HEDP)₃(H₂O)₂]·5H₂O (complex 1; HEDP = hydroxyethylidene diphosphonate; TPB = 1,3,5-tris(4-pyridyl)benzene) and (H-TPB)·[Zn₃(H-HEDP)(HEDP)(H₂O)]·2H₂O (complex 2) with distinguishable photochromism and tunable RTP are synthesized involving photoactive TPB molecules with different packing modes. Complex 1 exhibits bidirectionally on/off RTP regulation via on-switch with excitation of 250−330 nm light and off-switch with 350−380 nm, and the “turn-on” behavior can be attributed to the advance of Förster resonance energy transfer-assisted intersystem crossing (ISC) process while “turn-off” process due to the transformation from H₃-TPB cations to H₃-TPB^· radicals. Complex 2 exhibits photoswitchable RTP accompanied with reversible photochromism by leveraging the self-absorption and RTP emission. Two demos based on the above compounds are further applied to demonstrate the application in information recording and encryption fields. This work supplies a strategy toward the design of switchable RTP systems using electron transfer photochromism, shedding light on broadening the frontiers of photoresponsive materials.     

Highly Tuneable Photochromic Sodalites for Dosimetry,Security Marking and Imaging

Photochromic sodalites are considered for a plethora of possible applications, such as UV indexing and X-ray imaging, but for many of these the materials are yet to be optimized. UV indexing can be improved through incremental adjustment of the activation energy of coloration from 300 to 410 nm through replacement of sulfur with selenium. By combining this and other methods of tuning presented in the literature, the excitation threshold and photochromism color can be tuned independently of one another. The range of possible absorption maxima is expanded to 420–680 nm, or almost the entire visible spectrum. Mixing low-cost and easy-to-synthesize sodalites further broadens the possible range of colors and facilitates development of a unique sodalite mix capable of quantifying the doses of two types of UV radiation simultaneously. Finally, the response to X-rays of these highly tuned sodalites is investigated, and it is found that they can be sensitized to produce clear, high-contrast X-ray images at significantly lower doses of radiation than those required by classic photochromic sodalite, Na₈(AlSiO₄)₆(Cl,S)₂.