Effect of temperature on the intrinsic viscosity and conformation of chitosans in dilute HCl solution

Chen, Rong Huei; Tsaih, Min Larng

doi:10.1016/s0141-8130(98)00036-1

Cited by 145 publications

(73 citation statements)

References 25 publications

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“…The difference between our experimental values ( ) for malic acid) and this may be related to the fact that this model assumes that the chitosan chains are in a rigid rod conformation, so this result indicates that the chitosan in the present system is in semi-flexible coil conformation. For the range of pH and ionic strength used in the present work (Table 2), and accordingly to the work of Chen and Tsaih [61], chitosan chains with a molecular weight higher than 223 000 assume a less stretched conformation, indicating the adoption of a semi-flexible coil conformation instead of a rigid-rod.…”

Section: Rheological Characterizationmentioning

confidence: 52%

Untitled

2017

MSEIJ

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Chitosan is a biopolymer used in biomedical applications which has the ability to form lyotropic mesophases (chiral nematic) in several solvents. Currently, chitosan liquid crystalline phase is only observed at high polymer concentrations where the system has already transitioned to a gel-like state. Due to the non-homogenous mechanical behavior of a gel, it would be preferable to obtain a liquid crystalline phase while at solution state. Therefore, the formation of chitosan liquid-crystalline at solution state was investigated. Malic and hydrochloric aqueous solutions with different concentrations of chitosan were prepared and the gel formation was followed by rheological measurements. The concentration, C Gel , at which the gel is formed, was found to be dependent on the acid used, the malic aqueous solutions presenting higher C Gel . For the chitosan/malic acid system the chiral nematic mesophase appeared in solution and was preserved in the gel (for C>C Gel ) while for the chitosan/hydrochloric acid system, mesophase was only observed in gel. Using Polarized Optical Microscopy (POM) Swirl-like fingerprint textures typical of cholesteric mesophases were observed and the helical pitch was determined. The existence of mesophases in the gel, in both chitosan aqueous solutions, was also confirmed by rheometry.Keywords: Morphology; Rheology; Cholesteric; Liquid-crystals; Gels IntroductionChitin and chitosan are glycosaminoglycans with the rare property of bioactivity. These polysaccharides are in fact copolymers of β-(1→4)-linked 2-acetamido-2-deoxy-Dglucopyranose and 2-amino-2-deoxy-D-glucopyranose. The difference between the two is determined by the DA, the degree of acetylation, corresponding to the molar fraction of acetyl units constituting the polymer chains. It is considered that chitosan refers to polymers with DAs below 50 % (more commonly 10-30 %) [1]. Chitin is considered the second most abundant polymer in nature but due to its low solubility has limited applications and therefore is mostly used in the deacetylated form, as chitosan. Chitosan is the product of the alkali hydrolysis of chitin and is soluble in dilute acidic solutions [2]. The reason why chitosan presents a higher solubility than chitin is the presence of protonated free amine groups below pH 6.2 [3] and this polycation material has several applications in different fields, from agriculture, waste and water treatment, food and beverages, cosmetic and toiletries, biopharmaceuticals to biomedical applications [4,5]. In biomedical and pharmaceutical applications chitosan is used to produce hydrogels, due to its gelation properties. Several reports on literature can be found concerning the production of chemical [6,7] and physical [8,9] hydrogels from chitosan. Hamdine [10,11] reported an extensive work regarding chitosan gelation in different acids and concluded that chitosan has different behaviours when dissolved in acid malic and in hydrochloric acid. In the first case, due to the considerable volume of the acid molecule, that ...

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Section: Rheological Characterizationmentioning

confidence: 52%

Untitled

2017

MSEIJ

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“…The method of Chen and Tsaih (1998), was followed to determine the specific viscosity (η sp ). Each of chitosan samples was dissolved in mixture of acetic acid (0.1 M), and sodium chloride (0.2 M).…”

Section: 32-fourier Transform Infrared Spectroscopy (Ftir)mentioning

confidence: 99%

Role of Chitosan Extracted from Shrimp Waste in Controlling Tomato Blackmold Disease Caused by Alternaria alternata

Zian

2016

Journal of Applied Plant Protection

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Tomato suffers from several diseases at all stages of its life. Blackmold, caused by Alternaria alternate (Fr.) Keissler is one of the most important postharvest disease of tomato. The effect of various concentrations of chitosan solution on A. alternata the causal agent of blackmold disease of tomato fruits on mycelial growth was studied. The isolate was tested in vitro using PDA amended with seven concentrations of chitosan (0, 1, 2, 3, 4, 5 and 6 mg ml -). Chitosan significantly (P < 0.05) inhibited the radial mycelial growth of this fungus by 67.4% at 6 mg ml 1 concentration. Tomato fruits treated with aqueous solution of chitosan compared with the Ipromise ® fungicide (Thiophonate-methyl 20% + Iprodione 20%) was artificially inoculated with A. alternata and incubated at 8, 18 and 28°C. Lesion diameters and total phenolic contents were recorded 7 and 14-days after inoculation. Chitosan also, significantly (P < 0.05) reduced the lesion diameters of tomato fruits which were smaller for all treatments when stored at 8°C compared to the control treatment. Chitosan treatment resulted in the highest increase in total phenolic contents over the untreated control. Whereas a less increase in total phenolic contents was recognized in fungicide treatment. In all treatments, total phenolic contents increased first and declined at the end of storage. The results of this study indicate that chitosan was a alternative safe coating method especially when stored at low temperature degree for prevents tomato fruits blackmold disease which causes economic losses during transportation, marketing and storage.

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“…In modern times the most common technique has become size-exclusion chromatography (SEC). Apart from batch methods such as batch viscosity measurements (Nah & Jang, 2002), batch static light-scattering (SLS) measurements (Berth & Dautzenberg, 2002;Cölfen et al, 2001;Lamarque et al, 2005;Pa & Yu, 2001), or batch multi-angle light-scattering (MALS) measurements (Anthonsen et al, 1994;Chen & Tsaih, 1998;Tsaih & Chen, 1997), chromatography has the advantage of determining the polydispersity of the sample. The width of the molecular weight distribution is often the key parameter of a chitosan sample.…”

Section: W Determinationmentioning

confidence: 99%

“…The diagram (Fig. 2) presents values obtained at 436 nm (Wang et al 1991) and values obtained at 633 nm (Terbojevich et al, 1991;Christensen et al, 2008;Kasaai et al, 2000;Chen & Tsaih, 1998;Berth et al, 1998;Schatz et al, 2003) for different chitosan preparations with changing FA(DA). The reason for this change is that dn/dc enters the molecular weight calculation quadratically.…”

Section: W Determinationmentioning

confidence: 99%