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1.
Xyloglucan in water solution turns into a gel with addition of alcohol such as methanol and ethanol. In regard to this phenomenon,
we investigated the adhesive property of alcohol to xyloglucan and proposed the mechanism of the gelation by molecular dynamics
(MD) simulation of a xyloglucan in water, water/methanol, and water/ethanol solution for 10 ns. The alcohol molecules showed
its adhesive property to the xyloglucan and made the swelling-shrinking motion of the xyloglucan slow. Alcohol molecules solvated
to the xyloglucan mainly in hydrophobic way so as to fill the void of water hydration shell, resulting in reformation of the
hydrogen-bond network of water molecules around the solute. We also found that alcohol molecules have strong tendency to hydrogen-bond
on xylose O3 in xyloglucan. According to these results, we proposed the gelation mechanism of xyloglucan in water/alcohol
solution. 相似文献
2.
Simona Todaro Clelia Dispenza Maria Antonietta Sabatino Maria Grazia Ortore Rosa Passantino Pier Luigi San Biagio Donatella Bulone 《Journal of Polymer Science.Polymer Physics》2015,53(24):1727-1735
Xyloglucan is a natural polysaccharide having a cellulose‐like backbone and hydroxyl groups‐rich side‐chains. In its native form the polymer is water‐soluble and forms gel only in presence of selected co‐solutes. When a given fraction of galactosyl residues are removed by enzymatic reaction, the polymer acquires the ability to form a gel in aqueous solution at physiological temperatures, a property of great interest for biomedical/pharmaceutical applications. This work presents data on the effect of a temperature increase on degalactosylated xyloglucan dispersed in water at concentration low enough not to run into macroscopic gelation. Results obtained over a wide interval of length scales show that, on increasing temperature, individual polymer chains and pre‐existing clusters self‐assemble into larger structures. The process implies a structural rearrangement over a few nanometers scale and an increase of dynamics homogeneity. The relation of these findings to coil‐globule transition and phase separation is discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1727–1735 相似文献
3.
Xyloglucan is a type of hemicellulose with a cellulose backbone containing (1→6)-α-xylose or (1→2)-β-galactoxylose as a side chain. It is soluble in water. Its aqueous solution forms a gel or gel-like precipitate by addition
of Congo red. Xyloglucan gel structures with various concentrations of Congo red were observed by small angle X-ray scattering
(SAXS) at the nano-level. SAXS results indicated that the xyloglucan chains interacted with Congo red, and that an increase
of concentration of Congo red induced a characteristic cross-linking domain, which consisted of a flat structure containing
stacked xyloglucan chain assemblies. The Congo red molecules are inserted between the xyloglucan chains. 相似文献
4.
Katsuyoshi Nishinari 《Macromolecular Symposia》2000,159(1):205-214
Sol‐gel transition of dispersions of biopolymers, which are used widely in food, cosmetics, biomedical and related industries, is classified by the temperature dependence of storage shear modulus. Sol‐gel transition of gellan gum solution is described well by a criterion of Winter‐Chambon. Too fast gelation of dispersions of konjac glucomannan in the presence of excessive amount of alkaline coagulant and/or at higher temperatures leads to a formation of gels with lower modulus. A solution of xyloglucan from which a certain amount of galactose residues is removed forms a gel on heating and reverts into a solution on further heating. The lower temperature transition of this xyloglucan solution is induced by hydrophobic interaction. 相似文献
5.
Yoshiaki Yuguchi Takako Kumagai Min Wu Takahiro Hirotsu Jun Hosokawa 《Cellulose (London, England)》2004,11(2):203-208
Xyloglucan has a cellulose backbone with branched (16)--xylose or (12)--galactoxylose as a side chain. Its aqueous solution yields a gel by adding alcohol. The gel structure of xyloglucan ID various kinds of mono- or polyhydric alcohol/water systems was studied by small-angle X-ray scattering (SAXS). The gelation behavior ID strongly dependent on the type of alcohol. The SAXS from gel with monohydric alcohols indicated that the xyloglucan chains caused random aggregation, as expressed with a Debye–Bueche type scattering function. The type of alcohol added was correlated with the size of the inhomogeneity, as evaluated by SAXS results. The gelation with polyhydric alcohols resulted ID less association, which occurred as side-by-side association with a few xyloglucan chains, rather than as random aggregation. 相似文献
6.
A new tetrathiafulvalene (TTF) derivative with two cholesterol units (compound 1 ) was synthesized and characterized. Gelation of n‐hexane occurred after the hot solution of 1 was subjected to ultrasonic treatment for a few minutes. The resulting organogel was characterized with SEM, XRD and AFM. Besides heating the gel‐sol transition also occurred upon addition of I2 which can oxidize the TTF unit in 1 . This result provides a new example of organogels responding to redox reactions. Interestingly, gelation‐induced CD signals were observed and the CD signals can be tuned with the gel‐sol transition which can be effected by heating and chemical reaction with I2. 相似文献
7.
Katsuyoshi Nishinari BoSook Kim Yapeng Fang Yoko Nitta Makoto Takemasa 《Cellulose (London, England)》2006,13(4):365-374
Interaction between tamarind seed xyloglucan and the other polysaccharides, gellan gum or xanthan investigated by rheology, differential scanning calorimetry, and related methods was discussed. All these three polysaccharides do not form a gel at lower concentrations by itself at the experimental conditions studied but the gelation of xyloglucan occurs in the presence of gellan or xanthan. Gelation of xyloglucan in the presence of a polyphenol, epigallocatechin gallate, is also discussed. Hence the gelation of these mixtures is caused by the synergistic interaction, and the models for the synergistic interaction were discussed. The gelation of polysaccharides by the synergistic interaction is of great value for food and related industries. 相似文献
8.
Xyloglucan and pectin are major non-cellulosic components of most primary plant cell walls. It is believed that xyloglucan and perhaps pectin are functioning as tethers between cellulose microfibrils in the cell walls. In order to understand the role of xyloglucan and pectin in cell wall mechanical properties, model cell wall composites created using Gluconacetobacter xylinus cellulose or cellulose nanowhiskers (CNWs) derived there from with different amounts of xyloglucan and/or pectin have been prepared and measured under extension conditions. Compared with pure CNW films, CNW composites with lower amounts of xyloglucan or pectin did not show significant differences in mechanical behavior. Only when the additives were as high as 60 %, the films exhibited a slightly lower Young’s modulus. However, when cultured with xyloglucan or pectin, the bacterial cellulose (BC) composites produced by G. xylinus showed much lower modulus compared with that of the pure BC films. Xyloglucan was able to further reduce the modulus and extensibility of the film compared to that of pectin. It is proposed that surface coating or tethering of xyloglucan or pectin of cellulose microfibrils does not alone affect the mechanical properties of cell wall materials. The implication from this work is that xyloglucan or pectin alters the mechanical properties of cellulose networks during rather than after the cellulose biosynthesis process, which impacts the nature of the connection between these compounds. 相似文献
9.
Summary: We developed a novel method of producing polymer gels in aqueous solution using UV irradiation. Persulfates were effective photosensitive initiators of polymerization and/or gelation of acryloyl‐type monomers/polymers. The gelation was confirmed by an abrupt increase in light scattering intensity, 〈I(q)〉T, at the gelation point. The gelation method entails significant advantages: it does not need any cross‐linkers, temperature control (heating), and additives except the persulfate.
10.
Yongguang Li Keith Man‐Chung Wong Dr. Anthony Yiu‐Yan Tam Dr. Lixin Wu Prof. Dr. Vivian Wing‐Wah Yam Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8690-8698
A series of photochromic spironaphthoxazine derivatives has been designed, synthesized, and characterized by using 1H NMR spectroscopy, FAB mass spectrometry, and elemental analysis. Their photophysical and photochromic behavior have been investigated. Two of the compounds (G12‐en‐SA‐SO and G16‐en‐SA‐SO) have been shown to be capable of forming stable thermoreversible organogels in organic solvents, tested by the “stable‐to‐inversion of a test tube” method. Addition of p‐toluenesulfonic acid was found to induce the formation of stable organogels at concentrations below that of the critical gelation concentration (c.g.c.), with a concomitant change in color from colorless to purple. Transmission electron microscopy and scanning electron microscopy of the xerogels showed typical fibrous structures in the micrometer scale. The activation parameters for the bleaching reaction of G8‐en‐SA‐SO in the solution state and G16‐en‐SA‐SO in the gel state have been determined in ethanol through kinetic studies at various temperatures. The results showed that the rate of the bleaching reaction in the gel state was much slower than that in the solution state. 相似文献
11.
Shaomin Sun Timothy J. Foster William MacNaughtan John R. Mitchell Dominik Fenn Andreas Koschella Thomas Heinze 《Journal of Polymer Science.Polymer Physics》2009,47(18):1743-1752
2 to 4% aqueous solutions of regioselectively substituted 3‐mono‐O‐ethyl‐ ( 3‐EC ) and randomly substituted ethyl‐ ( EC ) cellulose show association and gelation above 50–60 and 20–30 °C, respectively. In contrast, almost no association or gelation was seen with regioselectively substituted 3‐mono‐O‐methoxyethyl cellulose ( 3‐MEC ). This could be assessed by eye and measured using the techniques of 1H high‐resolution nuclear magnetic resonance, oscillatory rheology, and micro‐differential scanning calorimetry (DSC). Several processes are thought to occur during association and gelation of EC and 3‐EC . These were separated with respect to temperature, to varying degrees, on cooling and have been modeled using DSC data. In accordance with other work in the literature, they are thought to be, on heating, the disassociation of structures in solution followed first by the formation of water cages and then by the association of hydrophobic moieties into a precipitate or gel. Contrasting with previous work (Haque and Morris, Carbohydr Polym 1993, 22, 161–173), the rheological measurements do not show “two distinct waves of structure formation” at the present concentrations and the DSC measurements show, on cooling, an extremely wide separation in temperature of the processes for the regioselectively substituted cellulose derivative 3‐EC . © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1743–1752, 2009 相似文献
12.
Jin Wu Shih‐Chien Chiu Eli M. Pearce T. K. Kwei 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):224-231
The effects of phenolic additives on the gelation behavior of gelatin gels were investigated using thermomechanical analysis (TMA) for study of gel‐melting temperature, dynamic mechanical analysis (DMA) for study of gel‐storage modulus and gel‐aging stability, viscometry for study of gelation time, and texture analyzer for study of gel strength and gel melting. Thermodynamically, the addition of 1,3‐benzenediol, 1,4‐benzenediol or 1,3,5‐benzenetriol favored the gelation process of gelatin solutions (increases in Tm and aging stability) due to the introduction of extra physical crosslinks among gelatin chains through hydrogen bonding, while the addition of 1,2‐benzenediol had a negative effect (decreases in Tm and aging stability) possibly due to intra‐hydrogen bonding of the additive molecule itself. All the phenolic compounds had little effect on gel moduli. Kinetically, the introduction of 1,2‐benzenediol or 1,4‐benzenediol slowed the gelation process, while introduction of catechin, a polyphenol, accelerated the first stage of the gelation process. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 224–231, 2001 相似文献
13.
Kazuhiko Yamatoya Mayumi Shirakawa Kazutami Kuwano Junko Suzuki Osamu Baba 《Macromolecular Symposia》1997,120(1):231-236
Xyloglucan is found in the primary cell walls of higher plants, where it plays important biological roles. It also exists in certain seeds, for example tamarind, as a reserve polysaccharide. Some xyloglucan oligosaccharides possess plant growth promotion activity. We prepared hydrolyzed xyloglucan from the tamarind seed xyloglucan using endo-(1 → 4)- β -glucanase and examined its effects on lipid metabolism in rats fed a high fat diet. Among the plasma lipids, total lipid, cholesterol, triglyceride and β - lipoprotein were each reduced 14 - 17% by hydrolyzed xyloglucan. Hydrolyzed xyloglucan significantly reduced both adipose tissue weight and plasma GOT. Among the hepatic lipids, total lipid, cholesterol, triglyceride and phospholipid were significantly reduced by hydrolyzed xyloglucan. These hypolipidemic effects may be important for the treatment and prevention of geriatric diseases, including diabetes and cardiac disorders. 相似文献
14.
We demonstrated in this study that mixing two short peptide‐based gelators with different aromatic capping groups would result in molecular hydrogels with enhanced mechanical property. We selected gelators of PTZ‐GFFY and Nap‐GFFY for the study. Both PTZ‐GFFY and Nap‐GFFY could independently form molecular hydrogel by a heating‐cooling process. However, the mechanical property of gels of PTZ‐GFFY and Nap‐GFFY was relatively weak with storage moduli (G′) of about 500 and 150 Pa, respectively. A two‐component gel of PTZ‐GFFY and Nap‐GFFY could also form by a heating‐cooling process. Surprisingly, the G′ value of the two‐component gel was about 5000 Pa , which was at least ten times bigger than that of each single‐component gel. This is a novel and simple strategy to improve the mechanical property of molecular hydrogels. 相似文献
15.
Zhifang Sun Fucong Lv Lujie Cao Lin Liu Yi Zhang Zhouguang Lu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(27):8055-8059
A new type of multistimuli‐responsive hydrogels cross‐linked by metal ions and biopolymers is reported. By mixing the biopolymer chitosan (CS) with a variety of metal ions at the appropriate pH values, we obtained a series of transparent and stable hydrogels within a few seconds through supramolecular complexation. In particular, the CS–Ag hydrogel was chosen as the model and the gelation mechanism was revealed by various measurements. It was found that the facile association of Ag+ ions with amino and hydroxy groups in CS chains promoted rapid gel‐network formation. Interestingly, the CS–Ag hydrogel exhibits sharp phase transitions in response to multiple external stimuli, including pH value, chemical redox reactions, cations, anions, and neutral species. Furthermore, this soft matter showed a remarkable moldability to form shape‐persistent, free‐standing objects by a fast in situ gelation procedure. 相似文献
16.
Multistimuli‐Responsive,Moldable Supramolecular Hydrogels Cross‐Linked by Ultrafast Complexation of Metal Ions and Biopolymers 下载免费PDF全文
Zhifang Sun Fucong Lv Lujie Cao Dr. Lin Liu Prof. Dr. Yi Zhang Prof. Dr. Zhouguang Lu 《Angewandte Chemie (International ed. in English)》2015,54(27):7944-7948
A new type of multistimuli‐responsive hydrogels cross‐linked by metal ions and biopolymers is reported. By mixing the biopolymer chitosan (CS) with a variety of metal ions at the appropriate pH values, we obtained a series of transparent and stable hydrogels within a few seconds through supramolecular complexation. In particular, the CS–Ag hydrogel was chosen as the model and the gelation mechanism was revealed by various measurements. It was found that the facile association of Ag+ ions with amino and hydroxy groups in CS chains promoted rapid gel‐network formation. Interestingly, the CS–Ag hydrogel exhibits sharp phase transitions in response to multiple external stimuli, including pH value, chemical redox reactions, cations, anions, and neutral species. Furthermore, this soft matter showed a remarkable moldability to form shape‐persistent, free‐standing objects by a fast in situ gelation procedure. 相似文献
17.
Mridula Nandi Binoy Maiti Soham Banerjee Priyadarsi De 《Journal of polymer science. Part A, Polymer chemistry》2019,57(4):511-521
We report an interesting class of fatty acid appended side‐chain phenylalanine (Phe) containing poly(methacrylate) homopolymers that undergo self‐assembly leading to gelation in selective organic hydrocarbons, due to association among the side‐chain functionalities. Fatty acids of different n‐alkyl chain lengths have been attached to the N‐terminal of the Phe‐based methacrylate and the corresponding homopolymers have been synthesized via reversible addition–fragmentation chain transfer polymerization. These homopolymers undergo gelation in selective organic hydrocarbons. The morphology of these organogels has been characterized by field emission scanning electron microscopy which revealed macroporous structure of the organogels. Viscoelastic properties of organogels and the thermoreversible gel‐to‐sol transition have been investigated by rheological measurements. Powder X‐ray diffraction study has been performed to understand the effect of long n‐alkyl chains on the gelation process. FTIR study reveals inter‐/intra‐chain hydrogen bonding which is the driving force of organogelation of the polymers in suitable solvents. In absence of hydrogen bonding interaction, hydrophobic association fails to direct the self‐assembly process and no gelation is observed. An interesting feature of the homopolymeric gelators is that it can selectively congeal the diesel part from an oil–water biphasic mixture, which might be useful in oil spill treatment. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 511–521 相似文献
18.
Remarkable Shape‐Sustaining,Load‐Bearing,and Self‐Healing Properties Displayed by a Supramolecular Gel Derived from a Bis‐pyridyl‐bis‐amide of L‐Phenyl Alanine 下载免费PDF全文
A series of bis‐amides decorated with pyridyl and phenyl moieties derived from L ‐amino acids having an innocent side chain (L ‐alanine and L ‐phenyl alanine) were synthesized as potential low‐molecular‐weight gelators (LMWGs). Both protic and aprotic solvents were found to be gelled by most of the bis‐amides with moderate to excellent gelation efficiency (minimum gelator concentration=0.32–4.0 wt. % and gel–sol dissociation temperature Tgel=52–110 °C). The gels were characterized by rheology, DSC, SEM, TEM, and temperature‐variable 1H NMR measurements. pH‐dependent gelation studies revealed that the pyridyl moieties took part in gelation. Structure–property correlation was attempted using single‐crystal X‐ray and powder X‐ray diffraction data. Remarkably, one of the bis‐pyridyl bis‐amide gelators, namely 3,3‐Phe (3‐pyridyl bis‐amide of L ‐phenylalanine) displayed outstanding shape‐sustaining, load‐bearing, and self‐healing properties. 相似文献
19.
TLC experiments have been performed to resolve the enantiomers of three β-blockers by complexation chiral TLC with Cu(II) cation and five l amino acids. Loading was carried out by using the Cu(II)–l amino acid complex as chiral mobile phase additive with untreated silica gel plates; by mixing the Cu complex with silica gel before preparing the TLC plates; by ascending development of untreated plates with solutions of the Cu complex; and by using a solution of Cu(II) acetate as mobile phase additive for plates prepared by mixing the l amino acid with silica gel. Spots were located by use of iodine vapour. 相似文献
20.
Lijun Fan Hou Chen Gaojian Lv Jinli Cao Yidong Fu 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3233-3239
Crosslinking copolymerization of butyl methacrylate with a small amount of divinylbenzene (DVB) was carried out using single‐electron transfer‐living radical polymerization initiated with carbon tetrachloride (CCl4) and catalyzed by Cu(0)/N‐ligand in N,N‐dimethylformamide to produce a highly oil‐absorbing gel. The polymerization, gelation process, and oil‐absorbing properties were studied in detail. Analysis of monomer conversion with reaction time showed that the polymerization followed first‐order kinetics for both linear and crosslinking polymerization before gelation. Higher levels of DVB led to earlier gelation and the influence of N‐ligand on gelation was also significant. Under optimal conditions, oil absorption of the prepared gel to chloroform could reach 42.1 g·g?1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3233–3239 相似文献