- Investigation on the aggregation behavior of photo-responsive system composed of 1-hexadecyl-3-methylimidazolium bromide and 2-methoxycinnamic acid
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A novel fluid system composed of 2-methoxycinnamic acid (trans-OMCA) and 1-hexadecyl-3-methylimidazolium bromide (C16mimBr) in an aqueous solution was investigated. The compounds trans-OMCA and C16mimBr in an aqueous solution can self-assemble and form viscoelastic worm-like micelles. The concentrations of trans-OMCA and C16mimBr have a significant influence on the rheological properties of the system. The samples were characterized by rheological measurements. The structural isomerization of trans-to-cis for trans-OMCA occurred after UV light irradiation. The transformation of the system after UV light irradiation was determined by UV-vis absorption spectroscopy, rheological measurement and cryo-TEM observation. Surface tension measurements were carried out to investigate the role of trans-OMCA and UV light in C16mimBr aqueous solution. Critical aggregation concentration (cac), effectiveness of surface tension reduction (Πcac), maximum excess surface concentration (Γmax) and minimum area occupied per surfactant molecule (as) were investigated. Critical packing parameter was introduced to express the mechanism of aggregation behavior transition.
- Du, Mingyong,Dai, Caili,Chen, Ang,Wu, Xuepeng,Li, Yuyang,Liu, Yifei,Li, Weitao,Zhao, Mingwei
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- A simple class of photorheological fluids: Surfactant solutions with viscosity tunable by light
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Photorheological (PR) fluids, i.e., those with light-tunable rheological properties, may be useful in a variety of applications, such as in sensors and microfluidic devices. Currently, the need to synthesize complex photosensitive molecules hampers the applicability of these fluids. Here, we report a simple class of PR fluids that require no special synthesis and can be easily replicated in any lab from inexpensive chemicals. The fluids consist of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), and the photoresponsive organic derivative, trans-ortho-methoxycinnamic acid (OMCA). Aqueous mixtures of CTAB and OMCA in basic solution self-assemble into long, wormlike micelles. Upon irradiation by UV light (400 nm), OMCA undergoes a photoisomerization from its trans to its cis form, which alters the molecular packing at the micellar interface. The result is to transform the long micelles into much shorter entities and, in turn, the solution viscosity decreases by more than 4 orders of magnitude. Small-angle neutron scattering (SANS) is used to confirm the dramatic reduction in micellar length. The extent of viscosity reduction in these PR fluids can be tuned based on the composition of the mixture as well as the duration of the irradiation.
- Ketner, Aimee M.,Kumar, Rakesh,Davies, Tanner S.,Elder, Patrick W.,Raghavan, Srinivasa R.
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- Substituent effects of cis-cinnamic acid analogues as plant growh inhibitors
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1-O-cis-Cinnamoyl-β-d-glucopyranose is one of the most potent allelochemicals that has been isolated from Spiraea thunbergii Sieb by Hiradate et al. It derives its strong inhibitory activity from cis-cinnamic acid (cis-CA), which is crucial for phytotoxicity. By preparing and assaying a series of cis-CA analogues, it was previously found that the key features of cis-CA for lettuce root growth inhibition are a phenyl ring, cis-configuration of the alkene moiety, and carboxylic acid. On the basis of a structure-activity relationship study, the substituent effects on the aromatic ring of cis-CA were examined by systematic synthesis and the lettuce root growth inhibition assay of a series of cis-CA analogues having substituents on the aromatic ring. While ortho- and para-substituted analogues exhibited low potency in most cases, meta-substitution was not critical for potency, and analogues having a hydrophobic and sterically small substituent were more likely to be potent. Finally, several cis-CA analogues were found to be more potent root growth inhibitors than cis-CA.
- Nishikawa, Keisuke,Fukuda, Hiroshi,Abe, Masato,Nakanishi, Kazunari,Taniguchi, Tomoya,Nomura, Takashi,Yamaguchi, Chihiro,Hiradate, Syuntaro,Fujii, Yoshiharu,Okuda, Katsuhiro,Shindo, Mitsuru
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p. 132 - 147
(2014/01/06)
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- Control of the Solid-state photodimerization of some derivatives and analogs of transcinnamic acid by ethylenediamine
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Some of double salts derived from ethylenediamine (en) and a variety of trans-cinnamic acids and their analogs underwent photodimerization in the solid state, giving predominantly β-truxinic dimers. X-Ray studies demonstrate that (a) the conformation of en is gauche for the highly photoreactive double salts (o-1b·en and m-le·en), whereas it is anti for lessphotoreactive o-la·en or photoinert Id·en and (b) for highly reactive o-lb·en and m-le·en, the monomer acid molecules are arranged in an overlap configuration and a reactive monomer pair is hydrogendashbonded to the same en molecule.
- Ito, Yoshikatsu,Borecka, Bozena,Olovsson, Gunnar,Trotter, James,Scheffer, John R.
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p. 6087 - 6090
(2007/10/02)
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- Photocyclization of Ortho-Substituted Cinnamic Acids
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Mono and di (i.e. 2,6) o-chloro- and o-methoxycinnamic acids undergo photocyclization to give the corresponding coumarins.The reaction occurs in aqueous and organic media, with a prototypical reaction giving evidence of being favored at pH > 6.Cyclization of the dimethoxy acid is relatively inefficient (Φ for the PSS = 0.0015), and a photostationary state of the cis/trans acids is formed early into the reaction.The photocyclization of the dichloro analog is more efficient (Φ exceeds 0.04) and therefore time dependent since product formation competes with trans/cis isomerization.Methyl o-chlorocinnamate also photocyclizes (Φ for the PSS = 0.0022 in acetonitrile) but the o-methoxy ester is virtually photoinert.It is proposed that the acid photocyclizes through intramolecular nucleophilic attack by the carboxylate group followed by heterolysis of the nucleofuge.Methyl o-chlorocinnamate appears to photocyclize through a cycloaddition of the carbonyl group followed by homolysis of the Cl and Me moieties, possibly through the intermediacy of a ketene as proposed by earlier workers.
- Terrian, Deborah L.,Mohammad, Taj,Morrison, Harry
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p. 1981 - 1984
(2007/10/02)
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- A Facile Ring-opening of Coumarins: Synthesis of Furopinnarin
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A facile synthesis of furopinnarin through ring-opening of coumarin is achieved in high yield.The ring opening has been successfully applied on a number of coumarins and furocoumarins to generalise the reaction.
- Kaul, S. K.,Sehgal, C. K.,Taneja, S. C.,Dhar, K. L.,Atal, C. K.
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p. 472 - 474
(2007/10/02)
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- Substituent Effects in the Reaction of t-Butylmagnesium Chloride with Substituted Ethyl Cinnamates. A Correlation with 13C NMR Chemical Shifts
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The reaction of t-butylmagnesium chloride with some substituted ethyl (E)-cinnamates gave mainly 1,3-, 1,4-, 1,2- and 1,4-addition products and minor amounts of 1,2- and 1,3-addition products.The relative amounts of 1,3-addition products has been shown to correlate with 13C NMR chemical shifts of C-α of the ethyl cinnamates.The correlation indicates that the regio selectivity of the reactions is to a great extent dependent of polar effects and that the t-butyl radical has a nucleophilic character.
- Jalander, Lars
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p. 419 - 428
(2007/10/02)
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