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Switchable solvent

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
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
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
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
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
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
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
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
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
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
Kang-Fei Hu, Xiao-Shan Ning, Jian-Ping Qu, Yan-Biao Kang
A regioselectivity switchable aerobic Wacker-Tsuji oxidation has been developed using catalytic tert-butyl nitrite as a simple organic redox cocatalyst. By solely switching the solvent, either substituted aldehydes or ketones could be prepared under mild aerobic conditions in good yields, respectively. A mechanistic explanation for the selectivity control is proposed.
September 21, 2018: Journal of Organic Chemistry
Xu-Qing Wang, Wei Wang, Wei-Jian Li, Li-Jun Chen, Rui Yao, Guang-Qiang Yin, Yu-Xuan Wang, Ying Zhang, Junlin Huang, Hongwei Tan, Yihua Yu, Xiaopeng Li, Lin Xu, Hai-Bo Yang
With the aim of mimicking biological machines, in which the delicate arrangement of nanomechanical units lead to the output of specific functions upon the external stimulus, the construction of dual stimuli-responsive rotaxane-branched dendrimers was realized in this study. Starting from a switchable organometallic [2]rotaxane precursor, the employment of a controllable divergent approach allowed for the successful synthesis of a family of rotaxane-branched dendrimers up to the third generation with 21 switchable rotaxane moieties located on each branch...
August 9, 2018: Nature Communications
Shuang Hu, Jiao Xue, Xiao Yang, Xuan Chen, Run-Qin Wang, Xiao-Hong Bai
A sodium dodecyl sulfate sensitized switchable solvent liquid-phase microextraction method was developed and applied to the preconcentration of active alkaloids in Rhizoma coptidis followed by high performance liquid chromatography determination. Before extraction, nonionic triethylamine was converted to its cationic form in the presence of carbon dioxide. Then, the ionic solvent carrying target analytes was once more reverted to its nonionic form by adding sodium hydroxide, as well as phase separation and analytes enrichment were realized simultaneously...
September 2018: Journal of Separation Science
Junyan Tan, Dandan Chong, Yue Zhou, Rong Wang, Xinhua Wan, Jie Zhang
Polyoxometalate (POM) H3 PMo12 O40 was coassembled with stimuli-responsive triblock copolymer poly(ethylene oxide)- block-polystyrene- block-poly(2-(dimethylamino)ethyl methacrylate) (PEO- b-PS- b-PDMAEMA) by electrostatic interactions. Depending on the POM contents, the hybrid complexes can self-assemble into a series of morphologies: micelles, rods, toroids, and vesicles. Unlike traditional morphology transition of amphiphilic block copolymer derived from a broad range of hydrophobic volume fractions, POM-induced morphology transitions just occurred in a narrow range of volume fractions...
July 31, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Anton A Nechaev, Kristof Van Hecke, Manzoor Zaman, Stepan Kashtanov, Liviu Ungur, Olga P Pereshivko, Vsevolod A Peshkov, Erik V Van der Eycken
A gold-catalyzed post-Ugi ipso-cyclization for the diastereoselective synthesis of spirocyclic pyrrol-2-one-dienone system is described. Tuning the catalytic system, solvent, and temperature allowed selectively attaining two sets of diastereoisomers. The scope of the process has been evaluated, and a putative mechanistic model was proposed.
August 3, 2018: Journal of Organic Chemistry
Zhipeng Chen, Lingfeng Wang, Shuang Qiu, Shijian Ge
Biofuels produced from microalgal biomass have received growing worldwide recognition as promising alternatives to conventional petroleum-derived fuels. Among the processes involved, the downstream refinement process for the extraction of lipids from biomass greatly influences the sustainability and efficiency of the entire biofuel system. This review summarizes and compares the current techniques for the extraction and measurement of microalgal lipids, including the gravimetric methods using organic solvents, CO2 -based solvents, ionic liquids and switchable solvents, Nile red lipid visualization method, sulfo-phospho-vanillin method, and the thin-layer chromatography method...
2018: BioMed Research International
Wei-Ming Liao, Jian-Hua Zhang, Shao-Yun Yin, He Lin, Xingmin Zhang, Jihong Wang, Hai-Ping Wang, Kai Wu, Zheng Wang, Ya-Nan Fan, Mei Pan, Cheng-Yong Su
Two-dimensional (2D) metal-organic frameworks have exhibited a range of fascinating attributes, of interest to numerous fields. Here, a calcium-based metal-organic framework with a 2D layered structure has been designed. Dual emissions relating to intralayer excimers and interlayer trapped excitons are produced, showing excitation-dependent shifting tendency, characteristic of a low dimensional semiconductor nature. Furthermore, the layer stacking by weak van der Waals forces among dynamically coordinated DMF molecules enables exfoliation and morphology transformation, which can be achieved by ultrasound in different ratios of DMF/H2 O solvents, or grinding under appropriate humidity conditions, leading to nano samples including ultrathin nanosheets with single or few coordination layers...
June 19, 2018: Nature Communications
Merve Fırat, Süleyman Bodur, Büşra Tışlı, Cansu Özlü, Dotse Selali Chormey, Fatma Turak, Sezgin Bakırdere
In this study, a switchable solvent was used to preconcentrate trace amounts of Cd from aqueous solution for its determination by flame atomic absorption spectrometry (FAAS). Protonation of N,N-dimethylbenzylamine by dry ice (solid CO2 ) made it water soluble, and addition of sodium hydroxide converted it back to its original nonionic state for phase separation and subsequent extraction of Cd. A slotted quartz tube (SQT) was attached to the flame burner head to increase the residence time of Cd atoms in the light path...
June 12, 2018: Environmental Monitoring and Assessment
Linda E Franken, Yuchen Wei, Jiawen Chen, Egbert J Boekema, Depeng Zhao, Marc C A Stuart, Ben L Feringa
Control over dynamic functions in larger assemblies is key to many molecular systems, ranging from responsive materials to molecular machines. Here we report a molecular motor that forms bowl-shaped particles in water and how confinement of the molecular motor affects rotary motion. Studying the aggregation process in a broader context, we provide evidence that, in the case of bowl-shaped particles, the structures are not the product of self-assembly, but a direct result of the mixing a good solvent and a (partial) non-solvent and highly independent of the molecular design...
June 27, 2018: Journal of the American Chemical Society
Pesach Perlin, Eric G Gharakhanian, Timothy J Deming
Homoallylglycine N-carboxyanhydride, Hag NCA, monomers were synthesized and used to prepare polypeptides containing Hag segments with controllable lengths of up to 245 repeats. Poly(l-homoallylglycine), GHA, was found to adopt an α-helical conformation, which provided good solubility in organic solvents and allowed high yield functionalization of its alkene side-chains via radical promoted addition of thiols. The conformations of these derivatives were shown to be switchable between α-helical and disordered states in aqueous media using thioether alkylation or oxidation reactions...
June 12, 2018: Chemical Communications: Chem Comm
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