Effects of Acetone, Ethanol, Isopropanol and Dimethyl Sulfoxide on Amylose-Iodine Complex†

Barrett, Albert J.; Barrett, Karen L.; Khan, Arshad

doi:10.1080/10601329808000974

Cited by 6 publications

(5 citation statements)

References 17 publications

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“…This is a plausible explanation as CS is made of alternating semi-crystalline and amorphous layers of biopolymers amylose and amylopectin [27], being respectively slightly and mostly soluble in cold water [28] but less and less soluble as ethanol is added to the solvent [e.g. 29,30] until being insoluble in ethanol [31]. Fig.…”

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confidence: 99%

Dramatic effect of fluid chemistry on cornstarch suspensions: Linking particle interactions to macroscopic rheology

et al. 2017

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Suspensions of cornstarch in water exhibit strong dynamic shear-thickening. We show that partly replacing water by ethanol strongly alters the suspension rheology. We perform steady and nonsteady rheology measurements combined with atomic force microscopy to investigate the role of fluid chemistry on the macroscopic rheology of the suspensions and its link with the interactions between cornstarch grains. Upon increasing the ethanol content, the suspension goes through a yield-stress fluid state and ultimately becomes a shear-thinning fluid. On the cornstarch grain scale, atomic force microscopy measurements reveal the presence of polymers on the cornstarch surface, which exhibit a cosolvency effect. At intermediate ethanol content, a maximum of polymer solubility induces high microscopic adhesion which we relate to the macroscopic yield stress.Suspensions are mixtures of undissolved particles in a liquid. They are literally found all around us: mud, paints, pastes and blood [1]. The viscosity of a dense suspension can vary by orders of magnitude in a small shear rate interval [2]. Subjected to an increasing shear rate, dense suspensions first tend to become less viscous (shear-thinning) and then more viscous (shearthickening). The viscosity of some suspensions, especially non-Brownian ones, may increase so much that they effectively become solid [3]. Although standard rheology measurements provide a great tool to study this phenomenon [e.g. 4, 5], they are mainly limited to steadystate conditions.Many studies point out that dense suspensions exhibit remarkable dynamic phenomena emerging under non-steady-shear conditions: stable holes in thin vibrated layers [6], non-monotonic settling [7], dynamic compaction front [8] or fracturing [3]. Oscillatory rheology helps to describe some of these dynamic behaviours [9], but remains limited to constant volume conditions. Dynamic shear-thickening has been widely investigated [10], but its physical origin remains an active debate. Although several parameters seem to contribute to it (e.g. particles size [11], shape [12] or roughness [13]), it has become increasingly clear that frictional and non-contact interactions between particles play a key role [14,15]. Such interactions are easily modified in numerical simulations, but present a real challenge in experiments. Consequently, only few experimental studies addressthe role of particle-particle interactions in dense suspensions rheology [e.g. 5, 16] however lacking systematic variation of these interactions. Moreover, direct measurements of these interactions in relation to the rheology are also lacking so far.Here, we directly probe the microscopic interactions between individual particles and explore their link with * adeline.pons@normalesup.org the macroscopic rheology for dense cornstarch (CS) suspensions. The archetypical suspension of CS grains in water exhibits a strong dynamic shear-thickening [3,[6][7][8]. Interestingly, Taylor [17] shows that replacing water by polypropylene glycol in CS suspensions completely su...

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Dramatic effect of fluid chemistry on cornstarch suspensions: Linking particle interactions to macroscopic rheology

et al. 2017

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“…5,13 It has also been reported that presence of nonaqueous solvent in which iodine is highly soluble does not favor complexation of iodine with polymers. 9,14 It is well-established that polymers can induce micellization of anionic surfactants at much lower concentration than their normal critical micelle concentration (cmc) values. [15][16][17] On the other hand, addition of ionic surfactants to moderately concentrated solutions of nonionic polymers has been reported to substantially increase the viscosity of the solution even leading to formation of gels.…”

Section: Introductionmentioning

confidence: 99%

“…Because of low solubility of iodine in pure water, polymer−iodine complexes have generally been studied in presence of added potassium iodide, which enhances the solubility of iodine in water. Investigations on the PVA−iodine complex in aqueous media revealed that while increase in intermolecular hydrogen bonding favors the complex formation, the presence of gels or microgels inhibits the complex. , It has also been reported that presence of nonaqueous solvent in which iodine is highly soluble does not favor complexation of iodine with polymers. , …”

Section: Introductionmentioning

confidence: 99%

Effect of an Anionic Surfactant on the Complexation of Some Nonionic Polymers with Iodine in Aqueous Media

Naorem

Singh

2007

J. Phys. Chem. B

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Complexation of some water soluble nonionic polymers, namely, polyvinylalcohol (PVA), polyvinylpyrrolidone (PVP), and hydroxypropyl cellulose (HPC), with iodine has been studied in aqueous and aqueous sodiumdodecylsulfate (SDS) solution. While the complexation was indicated by a red shift of the tri-iodide band in case of PVP or HPC, the PVA-iodine complex showed its characteristic band around 500 nm. It was observed for the first time that presence of SDS led to complete break down of the PVA-iodine complex and its characteristic blue color. The presence of monomers of SDS, however, appeared to favor the formation of the iodine complex with PVP or HPC. Addition of n-propanol, which is known to prevent the formation of gels or microgels in polymer solutions, was found to enhance the polymer-iodine complex. Gels of pure HPC and HPC with iodine both in presence and absence of SDS have been prepared and studied.

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“…Amylose (AM) is the essentially unbranched fraction of starch, consisting of α- d -(1−4) glycosidic bonds. It is well-known that the AM can form inclusion complexes with amphiphilic compounds such as iodine − and surfactants. − In a complex, the hydrophobic part of the guest molecule is inserted into the central, hydrophobic cavity of the AM helices.…”

Section: Introductionmentioning

confidence: 99%

Gels of Hydrophobically Modified Hydroxyethyl Cellulose Cross-Linked by Amylose. Competition with Cyclodextrin

Karlberg

Piculell²,

Ragout³

2006

Langmuir

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Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. In this work, the competition between AM and cyclodextrin (CD) for the formation of inclusion complexes with hydrophobically modified hydroxyethyl cellulose (HMHEC) is investigated. A detailed study of viscosity, NMR self-diffusion, and chemical shifts of the two-component mixture, CD and HMHEC, was performed. The results imply that 2:1 (CD:polymer hydrophobe) complexes may be formed. The three-component mixtures, HMHEC/AM/CD, were investigated by rheology, NMR self-diffusion, and intensities of the NMR resonance peaks. The CD molecules competed efficiently with the AM molecules, as seen by a decreased storage modulus, an increased self-diffusion of AM and HMHEC, and increased NMR intensities of the HMHEC hydrophobes, as the concentration of CD increased in the solution. A high concentration of CD is needed in the mixtures to inhibit all interactions between HMHEC and AM, and it was shown that there still is an effect of AM at excess CD concentration in the mixtures.

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Effects of Acetone, Ethanol, Isopropanol and Dimethyl Sulfoxide on Amylose-Iodine Complex†

Cited by 6 publications

References 17 publications

Dramatic effect of fluid chemistry on cornstarch suspensions: Linking particle interactions to macroscopic rheology

Dramatic effect of fluid chemistry on cornstarch suspensions: Linking particle interactions to macroscopic rheology

Effect of an Anionic Surfactant on the Complexation of Some Nonionic Polymers with Iodine in Aqueous Media

Gels of Hydrophobically Modified Hydroxyethyl Cellulose Cross-Linked by Amylose. Competition with Cyclodextrin

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