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1.
A new synthetic protocol for the synthesis of large diameter (2.5 to 5 μm), temperature-, and pH-responsive microgels via
aqueous surfactant-free radical precipitation copolymerization is presented. We have found that in this size range, which
is not typically attainable using traditional dispersion polymerization approaches, excellent monodispersity and size control
are achieved when the synthesis employs a programmed temperature ramp from 45 to 65 °C during the nucleation stage of the
polymerization. A combined kinetic and thermodynamic hypothesis for large particle formation under these conditions is described.
Particle sizes, volume phase transition temperatures, and pH responsivity were characterized by particle tracking and photon
correlation spectroscopy to illustrate their similar behavior to particles made via more traditional routes. These particles
have been enabling for various studies in our group where microscopic visualization of the particles is required. 相似文献
2.
Shuai Wang Haichang Ding Yuesong Wang Congbin Fan Gang Liu Shouzhi Pu 《Tetrahedron》2019,75(11):1517-1524
A new multi-responsive fluorescent switch DTE-Pip-Rho 1O has been designed and synthesized in this study. For this molecule, the reactive site of spirolactam ring is far away from the diarylethene unit through the intramolecular piperazine. It exhibited high selectivity and sensitivity to Hg2+ in addition to obvious color change (colorless-pink) and fluorescence “off-on” (dark-orange) during this process. It is believed that the color change is due to Hg2+-assisted hydrolysis of rhodamine hydrazide. Therefore, the new molecule can be used as colorimentric and fluorescent chemosensor for Hg2+ with high selectivity. The detection limits of absorbance and fluorescence for Hg2+ were calculated to be 1.15?μM and 1.16?μM, respectively. The resulting DTE-Pip-Rho 1O-Hg2+ could also function as a reversible fluorescence photo-switch in response to UV/vis light owing to FRET mechanism. Moreover, it has been demonstrated that the photo-switchable system displayed excellent fatigue resistance and remarkable anti-photobleaching capability. 相似文献
3.
Aaron D. W. Kennedy Isolde Sandler Prof. Joakim Andréasson Dr. Junming Ho Dr. Jonathon E. Beves 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1103-1110
Three visible-light responsive photoswitches are reported, azobis(1-methyl-benzimidazole) ( 1 ), azobis(benzoxazole) ( 2 ) and azobis(benzothiazole) ( 3 ). Photostationary distributions are obtained upon irradiation with visible light comprising approximately 80 % of the thermally unstable isomer, with thermal half-lives up to 8 min and are mostly invariant to solvent. On protonation, compound 1 H+ has absorption extending beyond 600 nm, allowing switching with yellow light, and a thermal half-life just under 5 minutes. The two isomers have significantly different pKa values, offering potential as a pH switch. The absorption spectra of 2 and 3 are insensitive to acid, although changes in the thermal half-life of 3 indicate more basic intermediates that significantly influence the thermal barrier to isomerization. These findings are supported by high-level ab initio calculations, which validate that protonation occurs on the ring nitrogen and that the Z isomer is more basic in all cases. 相似文献
4.
Xingguo Liang Dr. Nobutaka Takenaka Hidenori Nishioka Hiroyuki Asanuma Prof. Dr. 《化学:亚洲杂志》2008,3(3):553-560
A new photoswitch for DNA hybridization involving para‐substituted azobenzenes (such as isopropyl‐ or tert‐butyl‐substituted derivatives) with L ‐threoninol as a linker was synthesized. Irradiation of the modified DNA with visible light led to dissociation of the duplex owing to the destabilization effect of the bulky substituent on the trans‐azobenzene. In contrast, trans‐to‐cis isomerization (UV light irradiation) facilitated duplex formation. The direction of this photoswitching mode was entirely reversed relative to the previous system with an unmodified azobenzene on D ‐threoninol whose trans form turned on the hybridization, and cis form turned it off. Such reversed and reversible photoswitching of DNA hybridization was directly demonstrated by using fluorophore‐ and quencher‐attached oligonucleotides. Furthermore, it was revealed that the cis‐to‐trans thermal isomerization was greatly suppressed in the presence of the complementary strand owing to the formation of the more‐stable duplex in the cis form. 相似文献
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This study presents analyses of deformations in nonlinear viscoelastic beams that experience large displacements and rotations due to mechanical, thermal, and electrical stimuli. The studied beams are relatively thin so that the effect of the transverse shear deformation is neglected, and the stretch along the transverse axis of the beams is also ignored. It is assumed that the plane that is perpendicular to the longitudinal axis of the undeformed beam remains plane during the deformations. The nonlinear kinematics of the finite strain beam theory presented by Reissner [27] is adopted, and a nonlinear viscoelastic constitutive relation based on a quasi-linear viscoelastic (QLV) model is considered for the beams. Deformation in beams due to mechanical, thermal, and electric field inputs are incorporated through the use of time integral functions, by separating the time-dependent function and nonlinear measures of field variables. The nonlinear measures are formulated by including higher order terms of the field variables, i.e. strain, temperature, and electric field. Responses of beams under mechanical, thermal, and electrical stimuli are illustrated and the effects of nonlinear constitutive relations on the overall deformations of the beams are highlighted. 相似文献
7.
DTE-BODIPY 2 and BTD-DTE 3 were designed for reversible light modulation of electron- and energy-transfer processes on TiO2, and showed almost complete ring closure. In BTD-DTE 3 the BTD is an acceptor group in the open form (OF), and an energy donor group in the closed form (CF), but this property is depending on the solvent. Quantum yields for ring closure decreased (BTD-DTE 3: factor 5; DTE-BODIPY 2: factor 12) compared to DTE 1, because of π-system elongation in OFs, and also cycloreversion quantum yields became smaller (BTD-DTE 3: factor 1.4; DTE-BODIPY 2: factor 2.2). 相似文献
8.
Novel hydrogels based on core-shell structured macro-crosslinkers were synthesized,which exhibited high toughness and multiple responsiveness.Sodium dodecyl sulfate (SDS) micelles mediated by NaC1 were used to encapsulate hydrophobic stearyl methacrylate (C18) in the core,and hydrophilic 2-acrylamido-2-methyl-1-propanesulfonic (AMPS)monomers in the corona.Such core-shell micelles were simultaneously copolymerized with acrylamide monomers through free radical polymerization.As a result,hydrogels crosslinked by amphiphilic "poly(C 18)-PAMPS" macro-crosslinkers were obtained.These hydrogels showed excellent tensile and compression strength and toughness.Cyclic compression loadingunloading tests demonstrated that the hydrogels were of outstanding fatigue resistance,and showed partial damage of energy dissipation mechanism.The damaged energy dissipation mechanism could be recovered at room temperature and the recovery could be accelerated at elevated temperatures.The hydrogels were sensitive to the change in pH and ion strength,showing reversible swelling/deswelling behaviors. 相似文献
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本文首先介绍了CdS光敏电阻光照特性的一种测试方法,然后设计了两个应用实验,一个是通过光敏电阻测量玻璃砖的光吸收系数,另一个是运用光敏电阻来控制蜂鸣器报警与路灯照明,并给出实验结果. 相似文献