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Switchable solvent

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https://read.qxmd.com/read/30785077/in-situ-probing-of-switchable-nanomechanical-properties-of-responsive-high-density-polymer-brushes-on-poly-dimethylsiloxane-an-afm-nanoindentation-approach
#1
K Jalili, F Abbasi, L Behboodpour
Nanomechanical characteristics of end grafted polymer brushes were studied by AFM based, colloidal probe nanoindentation measurements. A high-density polymer brush of poly(2-hydroxyethyl methacrylate) (PHEMA) was precisely prepared on the surface of a flexible poly(dimethylsiloxane) (PDMS) substrate oxidized in ultraviolet/ozone (UVO). Exposure times less than 10min resulted in laterally homogeneous oxidized surfaces, characterized by a SiOx thickness ∼35nm and an increased modulus up to 9MPa, as shown by AFM nanoindentation measurements...
February 6, 2019: Journal of the Mechanical Behavior of Biomedical Materials
https://read.qxmd.com/read/30732771/stimuli-responsive-cellulose-paper-materials
#2
REVIEW
Zhijian Li, Xiaohan Yang, Wei Li, Hanbin Liu
Cellulose paper derived from plants has served as a carrier of cultural inheritance since it was invented 2000 years ago. It attracted more and more attentions in recent years working as a versatile platform to develop functional materials because of its good flexibility, sustainability, biodegradability, low cost and great capability to be modified. Once be functionalized, such as modified with stimuli-responsive polymers, small molecules or inorganic particles, papers may be sensitive to external stimuli from environments and consequently find applications in wide ranges including protein separation, controlled drug release, switchable surfaces, sensoring devices and smart substrates with various colors, etc...
April 15, 2019: Carbohydrate Polymers
https://read.qxmd.com/read/30723880/an-accurate-and-sensitive-analytical-strategy-for-the-determination-of-palladium-in-aqueous-samples-slotted-quartz-tube-flame-atomic-absorption-spectrometry-with-switchable-liquid-liquid-microextraction-after-preconcentration-using-a-schiff-base-ligand
#3
Merve Fırat, Emine Gülhan Bakırdere
This study presents a green analytical method for palladium determination by slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS) following switchable liquid-liquid microextraction (SLLME). Efficient extraction of palladium was facilitated by complexation with a Schiff base ligand, synthesized specifically for this study. A three-stage thorough optimization procedure was carried out to boost the absorbance output of palladium. Complex formation was the first stage, and parameters evaluated included buffer solution pH and amount, concentration of ligand, and mixing period...
February 5, 2019: Environmental Monitoring and Assessment
https://read.qxmd.com/read/30675973/2-2-diamino-6-6-diboryl-1-1-binaphthyl-a-versatile-building-block-for-temperature-dependent-dual-fluorescence-and-switchable-circularly-polarized-lumincescence
#4
Zuo-Bang Sun, Jun-Kai Liu, Da-Fei Yuan, Zheng-Hua Zhao, Xiao-Zhang Zhu, Di-Hong Liu, Qian Peng, Cui-Hua Zhao
The temperature-dependent dual fluorescence and switchable circularly polarized luminescence (CPL) are two highly pursued but challenging properties for small organic molecules (SOMs). We herein disclose a triarylborane π-system based on a 2,2'-diamino-6,6'-diboryl-1,1'-binaphthyl scaffold, which can serve as a versatile building block to achieve these two properties by simply choosing different amino groups. The BNMe2-BNaph with less bulky dimethylamino groups displays temperature-dependent dual fluorescence, enabling the great utility as the highly sensitive ratiometric fluorescence thermometer...
January 24, 2019: Angewandte Chemie
https://read.qxmd.com/read/30657673/guest-dependent-dynamics-in-a-3d-covalent-organic-framework
#5
Yichong Chen, Zhao-Lin Shi, Lei Wei, Beibei Zhou, Jing Tan, Hao-Long Zhou, Yue-Biao Zhang
Guest-dependent dynamics having both crystal contraction and expansion upon inclusion of various guests is uncovered in a 3D covalent organic framework (COF) prepared with a facile and scalable method. A molecular-level understanding of how the framework adjusts the node geometry and molecular configuration to perform significant contraction and large amplitude expansion are resolved through synchrotron in-house powder X-ray diffraction (PXRD) and Rietveld refinements. We found that the COF adopts a contracted phase at ambient conditions upon capturing moisture and is also adaptive upon inclusion of organic solvents, which is highlighted by a large crystal expansion (as large as 50% crystallographic volume increment and a 3-fold channel size enlargement)...
January 18, 2019: Journal of the American Chemical Society
https://read.qxmd.com/read/30624072/a-ph-switchable-electrostatic-catalyst-for-the-diels-alder-reaction-progress-towards-synthetically-viable-electrostatic-catalysis
#6
Mitchell Tabrum Blyth, Michelle L Coote
Density functional theory calculations at the SMD/M06-2X/6-31+G(d,p)//M06-2X/6-31G(d) level of theory have been used to computationally design and test a pH-switchable electrostatic organocatalyst for Diels-Alder reactions. The successful cata-lyst design, bis(3-(3-phenylureido)benzyl)ammonium, was studied for the reaction of p-quinone with range of cyclic, hetero-cyclic and acyclc dienes and also the reaction of cyclopentadiene with maleimide and N-phenylmaleimide. All reactions showed significant enhancements in catalysis (10-32 kJ mol-1 in barrier lowering) when the catalyst was protonated, con-sistent with electrostatic stabilization of the transition state...
January 9, 2019: Journal of Organic Chemistry
https://read.qxmd.com/read/30624027/versatile-and-switchable-responsive-properties-of-a-lanthanide-viologen-metal-organic-framework
#7
Teng Gong, Qi Sui, Peng Li, Xian-Fu Meng, Li-Jiao Zhou, Jinquan Chen, Jianhua Xu, Lin Wang, En-Qing Gao
Metal-organic frameworks (MOFs) provide intriguing platforms for the design of responsive materials. It is challenging to mobilize as many components as possible of a MOF to collaboratively accomplish multiple responsive properties. Here, reversible photochromism, piezochromism, hydrochromism, ionochromism, and luminescence modulation of an ionic Eu(III) MOF is reported furnished by cationic electron-deficient viologen units and exchangeable guest anions. Mechanistically, the extraordinarily versatile responsive properties are owed to electron transfer (ET), charge transfer (CT), and energy transfer, involving viologen as electron acceptor, anion as electron donor, luminescing Eu(III) as energy donor, and anion-viologen CT complex or ET-generated radical as energy acceptor (luminescence quencher)...
January 9, 2019: Small
https://read.qxmd.com/read/30615436/electronically-triggered-switchable-binding-modes-of-the-c-organonitroso-arno-moiety-on-the-ru-acac-2-platform
#8
Sanchaita Dey, Sanjib Panda, Prabir Ghosh, Goutam Kumar Lahiri
This work evaluated the switchable binding profile of the biochemically relevant and redox non-innocent C-organonitroso (ArNO) moiety with the selective {Ru(acac)2 } (acac = acetylacetonate) metal fragment as a function of external stimuli, including the solvent medium (EtOH versus toluene) and aryl substituents (C6 H5 , p-OMe-C6 H4 , and p-Cl-C6 H4 ) in the framework of ArNO. In this context, the reaction of ArNO (Ar = C6 H5 or p-OMe-C6 H4 ) with the metal precursor RuII (acac)2 (CH3 CN)2 in polar protic EtOH led to the formation of monomeric [RuII (acac)2 (ArNOo )2 ] (1a or 1b) with η1 -N-bonded terminal ArNOo and double-ArNOo -bridged dimeric [(acac)2 RuII (μ-ArNOo )2 RuII (acac)2 ], 2a or 2b, respectively...
January 7, 2019: Inorganic Chemistry
https://read.qxmd.com/read/30543209/viscoelastic-change-of-block-copolymer-ion-gels-in-a-photo-switchable-azobenzene-ionic-liquid-triggered-by-light
#9
Caihong Wang, Kei Hashimoto, Ryota Tamate, Hisashi Kokubo, Ken Morishima, Xiang Li, Mitsuhiro Shibayama, Fengniu Lu, Takashi Nakanishi, Masayoshi Watanabe
A photo-switchable ionic liquid solvent bearing an azobenzene moiety induced a viscoelastic change of block copolymer ion gels by light. ABA triblock copolymers having poly(phenethyl methacrylate) and poly(benzyl methacrylate) as A blocks exhibited opposite photoinduced rheological responses although they had only a tiny structural difference in the alkyl chain length.
December 13, 2018: Chemical Communications: Chem Comm
https://read.qxmd.com/read/30542815/solid-phase-extraction-coupled-with-switchable-hydrophilicity-solvent-based-homogeneous-liquid-liquid-microextraction-for-chloramphenicol-enrichment-in-environmental-water-samples-a-novel-alternative-to-classical-extraction-techniques
#10
Xin Di, Xin Wang, Youping Liu, Xingjie Guo, Xin Di
A simple and efficient method combining solid-phase extraction (SPE) with homogeneous liquid-liquid microextraction (HLLME) has been developed for fast pretreatment of chloramphenicol (CAP) from water samples prior to determination by high-performance liquid chromatography-ultraviolet detection. Oasis HLB sorbent was chosen for SPE. In HLLME, N,N-dimethylcyclohexylamine was used as a CO2 -triggered switchable solvent that could switch reversibly between hydrophilic and hydrophobic forms. The parameters influencing both SPE and HLLME were investigated and optimized...
December 12, 2018: Analytical and Bioanalytical Chemistry
https://read.qxmd.com/read/30461144/multicolor-emission-from-non-conjugated-polymers-based-on-a-single-switchable-boron-chromophore
#11
Junwei Wang, Nan Wang, Gang Wu, Suning Wang, Xiaoyu Li
Multicolor emissive and responsive materials are highly attractive due to their potential applications in various fields, and polymers are preferred for their good processability and high stability. Herein, we report a series of new polymers based on a methacrylate monomer containing a switchable boron chromophore. In spite of the unconjugated nature, interestingly, the homopolymers from this monomer display rare multicolor fluorescence in solution that is highly dependent on the degree of polymerization (DP)...
November 21, 2018: Angewandte Chemie
https://read.qxmd.com/read/30444347/flow-assisted-switchable-catalysis-of-metal-ions-in-a-microenvelope-system-embedded-with-core-shell-polymers
#12
Niraj K Vishwakarma, Yoon-Ho Hwang, Praveen Reddy Adiyala, Dong-Pyo Kim
Many efforts have been made on stimuli-responsive switchable catalysis to trigger catalytic activity over various chemical reactions. However, the reported light-, pH- or chemically responsive organocatalysts are mostly incomplete in the aspects of shielding efficiency and long-term performance. Here, we advance the flow-assisted switchable catalysis of metal ions in a microenvelope system that allows  the on-off catalysis mode on demand for long-lasting catalytic activity. Various metal-ion catalysts can be selectively embedded in a novel polymeric core-shell of the heteroarm star copolymer of poly(styrene) and poly(4-vinylpyridine) emanated from a polyhedral oligomeric silsesquioxane center...
November 29, 2018: ACS Applied Materials & Interfaces
https://read.qxmd.com/read/30354165/switchable-synthetic-strategy-toward-trisubstituted-and-tetrasubstituted-exocyclic-alkenes
#13
Sen Zhou, Fangyuan Yuan, Minjie Guo, Guangwei Wang, Xiangyang Tang, Wentao Zhao
An efficient and facile method for the construction of tri- or tetrasubstituted exocyclic alkenes is achieved via a Cu(I)-catalytic system. This protocol exhibits mild conditions, low-cost catalyst, good functional group tolerance, and good yields. The selectivity toward tri- or tetrasubstituted alkenes can be delicately controlled by adjustment of base and solvent. A preliminary mechanism study manifested that the reaction undergoes a radical process, where B2 pin2 plays an indispensable role.
November 2, 2018: Organic Letters
https://read.qxmd.com/read/30310576/switchable-gate-opening-effect-in-metal-organic-polyhedra-assemblies-through-solution-processing
#14
Gavin A Craig, Patrick Larpent, Shinpei Kusaka, Ryotaro Matsuda, Susumu Kitagawa, Shuhei Furukawa
Gate-opening gas sorption is known for metal-organic frameworks, and is associated with structural flexibility and advantageous properties for sensing and gas uptake. Here, we show that gate-opening is also possible for metal-organic polyhedra (MOPs), and depends on the molecular organisation in the lattice. Thanks to the solubility of MOPs, several interchangeable solvatomorphs of a lantern-type MOP were synthesised via treatment with different solvents. One phase obtained through use of methanol induced a gate-opening effect in the lattice in response to carbon dioxide uptake...
August 21, 2018: Chemical Science
https://read.qxmd.com/read/30229659/switchable-single-walled-carbon-nanotube-polymer-composites-for-co-2-sensing
#15
Bora Yoon, Seon-Jin Choi, Timothy M Swager, Gary F Walsh
We report a chemiresistive CO2 sensor based on single-walled carbon nanotubes (SWCNTs) noncovalently functionalized with a CO2 switchable copolymer containing amidine pendant groups that transform into amidinium bicarbonates in response to CO2 . To fabricate a robust surface-anchored polymer-SWCNT dispersion via spray coating, we first designed and synthesized a precursor copolymer, P(4VP-VBAz), bearing both 4-vinylpyridine (4VP) groups and azide groups. The SWCNT dispersant group, 4VP, is capable of debundling and stabilizing nanotubes to improve their solubility in organic solvents for solution processing...
October 3, 2018: ACS Applied Materials & Interfaces
https://read.qxmd.com/read/30223199/macroporous-monoliths-with-ph-induced-switchable-wettability-for-recyclable-oil-separation-and-recovery
#16
Zanru Guo, Hongjian Gu, Qiang Chen, Zhanfeng He, Wenyuan Xu, Jiali Zhang, Yongxin Liu, Leyan Xiong, Longzhen Zheng, Yujun Feng
HYPOTHESIS: The effective separation and recovery of oils from water is important for the protections of ecosystems and the environment. Polymeric porous monoliths have been demonstrated as attractive absorbents for oil/water separation. However, the recyclability was mainly realized by squeezing, combustion, or centrifugation, which may restrict in elastic materials, destroy the adsorbates or need special apparatus. Thus it is desirable to developing monoliths with controllable oil absorption and desorption...
January 15, 2019: Journal of Colloid and Interface Science
https://read.qxmd.com/read/30216692/tunable-fluorescence-from-a-responsive-hyperbranched-polymer-with-spatially-arranged-fluorophore-arrays
#17
Xiaosong Cao, Weiping Gan, Yi Shi, Hui Xu, Haifeng Gao
In the present study, a water-soluble hyperbranched polymer platform that contained a Förster resonance energy transfer (FRET) array and exhibited varied fluorescence in response to solvent, light, and CN- anion stimuli was constructed. The use of chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization (CuAACP) enabled accurate control of the ratio and distance of three incorporated fluorophores, coumarin (Cou), nitrobenzoxadiazole (NBD), and photoswitchable spiropyran (SP), that could be reversibly transformed into the red-emitting merocyanine (MC) state...
September 14, 2018: Chemistry, An Asian Journal
https://read.qxmd.com/read/30192035/light-induced-spin-transitions-in-copper-nitroxide-based-switchable-molecular-magnets-insights-from-periodic-dft-u-calculations
#18
Rocío Sánchez-de-Armas, Norge Cruz-Hernández, Carmen J Calzado
The electronic structure and magnetic interactions of three members of the breathing crystal Cu(hfac)2LR family, mainly Cu(hfac)2LPr (1), Cu(hfac)2LBu•0.5C8H18 (2) and Cu(hfac)2LBu•0.5C8H10 (3), have been analyzed by means of periodic plane-wave based DFT+U calculations. These Cu(II)-nitroxide based molecular magnets display thermally and optically induced switchable behaviour and light-induced excited spin state trapping phenomena. The calculations confirm the presence of temperature-dependent exchange interaction within the spin triads formed by the nitroxide-copper(II)-nitroxide units, in line with the changes observed in the effective magnetic moment...
September 7, 2018: Chemistry: a European Journal
https://read.qxmd.com/read/30133264/a-spin-crossover-molecular-material-describing-four-distinct-thermal-pathways
#19
Carlos Bartual-Murgui, Rosa Diego, Sergi Vela, Simon J Teat, Olivier Roubeau, Guillem Aromí
Spin-crossover (SCO) molecular solids are valued switchable materials for their common abrupt and reversible thermal transitions, large thermal hysteresis, or guest-dependent effects. These properties usually involve crystallographic transitions coupled to the SCO events. These phenomena are of great value for the understanding of solid-state transformations and also for exploiting them. We present here a lattice of the complex [FeL(bbp)](ClO4 )2 (1; L and bbp are tris-imine ligands) featuring an unprecedented rich succession of SCO and crystallographic phase transformations...
September 4, 2018: Inorganic Chemistry
https://read.qxmd.com/read/30123725/co-2-switchable-solvents-as-entrainer-in-fluid-separations
#20
Boelo Schuur, Mart Nijland, Marek Blahušiak, Alberto Juan
CO2 -switchable solvents, typically neutral solvents that switch with CO2 into ionic species, were investigated for use as entrainer in fluid separations such as extractive distillation. Their switchable nature was investigated, which may facilitate liquid-liquid extraction or extractive distillation as ionic liquid (IL), whereas during regeneration their decarboxylation into the amine form prevents temperature shoot-up. Studied elements included a property screening and detailed mechanistic and kinetic studies on the switching of 2-ethylhexylamine and N , N- benzyl methylamine...
August 6, 2018: ACS Sustainable Chemistry & Engineering
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