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RISS 인기검색어
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- 저자 : Congde (검색결과 5 건)
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Rheology and viscosity scaling of gelatin/1-allyl-3-methylimidazolium chloride solution
Congde Qiao,Tianduo Li,Ling Zhang,Xiaodeng Yang,Jing Xu 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.2
Gelatin/1-allyl-3-methylimidazolium chloride solutions are prepared by using the ionic liquid 1-allyl-3-methylimidazolium chloride as solvent. The rheological properties of the gelatin solutions have been investigatedby steady shear and oscillatory shear measurements. In the steady shear measurements, the gelatinsolutions with high concentration show a shear-thinning flow behavior at high shear rates, while anothershear thinning region can be found in the dilute gelatin solutions at low shear rates. The overlap concentrationof gelatin in [amim]Cl is 1.0 wt% and the entanglement concentration is a factor of 4 larger(4.0 wt%). The high intrinsic viscosity (295 mL/g) indicates that the gelatin chains dispersed freely in theionic liquid and no aggregation phenomenon occurs in dilute gelatin solution. The frequency dependencesof modulus changed obviously with an increase in gelatin concentration. The empirical time-temperaturesuperposition principle holds true at the experimental temperatures.
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Congde Qiao,Jianlong Zhang,Aiqun Kong 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.1
An investigation of the influences of pH, salt type, and salt concentration on the conformations of gelatin molecules in trivalent chromium salt solutions was performed by viscosity and dynamic light scattering (DLS) techniques. It was found that the viscosity behaviors as polyelectrolytes or polyampholytes depended on the charge distribution on the gelatin chains, which can be tuned by the value of pH of the gelatin solution. The intrinsic viscosity of gelatin in basic chromium sulfate aqueous solution at pH = 2.0 first decreased and then increased with increasing Cr(OH)SO4 concentration, while a monotonic decrease of the intrinsic viscosity of gelatin was observed in CrCl3 solution. However, the intrinsic viscosity of gelatin at pH = 5.0 was found to be increased first and then decreased with an increase in salt concentration in Cr(OH)SO4 solution, as well as in CrCl3 solution. We suggested that the observed viscosity behavior of gelatin in trivalent chromium salt solutions was attributed to the comprehensive effects of shielding, overcharging, and crosslinking (complexation) caused by the introduction of the different counterions. In addition, the average hydrodynamic radius (Rh) of gelatin molecules in various salt solutions was determined by DLS. It was found that the change trend of Rh with salt concentration was the same as the change of intrinsic viscosity. Based on the results of the viscosity and DLS, a possible mechanism for the conformational transition of gelatin chains with external conditions including pH, salt concentration, and salt type is proposed.
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Viscosity properties of gelatin in solutions of monovalent and divalent Salts
Congde Qiao,Guangxin Chen,Yulong, Li,Tianduo Li 한국유변학회 2013 Korea-Australia rheology journal Vol.25 No.4
The viscosity behaviors of gelatin with and without salts were examined in details by a rotational viscometer and a horizontal gravitational capillary viscometer, ranging from extremely dilute to entangled regimes. It was found that gelatin in salt free solution behaviors as neutral polymer in θ solvent. Polyelectrolyte effect can be found in extremely dilute regime. For gelatin/NaCl solution, the concentration dependence of specific viscosity showed that gelatin behaviors as neutral polymer in good solvent. The two critical concentration c* and ce of gelatin solutions with and without NaCl moved from 4.0 wt% and 14.0 wt% to 2.0 wt% and 12.0 wt%, respectively. Addition of salts can improve the gelatin viscosity. It is the characteristic of a polyampholyte. The viscosity increased more significantly in CaCl2 than that in NaCl solutions. Moreover, the effect of Ca2+ is notable in gelatin solution with high concentrations, especially in entangled solutions.
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Rheology and viscosity scaling of gelatin/1-allyl-3-methylimidazolium chloride solution
Qiao, Congde,Li, Tianduo,Zhang, Ling,Yang, Xiaodeng,Xu, Jing 한국유변학회 2014 Korea-Australia rheology journal Vol.26 No.2
Gelatin/1-allyl-3-methylimidazolium chloride solutions are prepared by using the ionic liquid 1-allyl-3-methylimidazolium chloride as solvent. The rheological properties of the gelatin solutions have been investigated by steady shear and oscillatory shear measurements. In the steady shear measurements, the gelatin solutions with high concentration show a shear-thinning flow behavior at high shear rates, while another shear thinning region can be found in the dilute gelatin solutions at low shear rates. The overlap concentration of gelatin in [amim]Cl is 1.0 wt% and the entanglement concentration is a factor of 4 larger (4.0 wt%). The high intrinsic viscosity (295 mL/g) indicates that the gelatin chains dispersed freely in the ionic liquid and no aggregation phenomenon occurs in dilute gelatin solution. The frequency dependences of modulus changed obviously with an increase in gelatin concentration. The empirical time-temperature superposition principle holds true at the experimental temperatures.
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Effect of Salts on the Thermal Stability of Physically Crosslinked Gelatin Hydrogels
Jianlong Zhang,Congde Qiao,Xianguang Ma,Weiliang Liu,Qinze Liu 한국고분자학회 2017 폴리머 Vol.41 No.4
The effects of preparation conditions, such as polymer concentration, annealing temperature, annealing time and pH, on the melting behavior of gelatin gels were investigated. An optimum condition of gel preparation for calorimetric test is obtained. In addition, the influence of salt including salt concentration and salt type on the melting behavior of gelatin gels was explored by DSC and rheometer. It was found that the melting temperature first increased and then decreased with an increase in salt concentration. This result indicates that electrostatic interactions are important for the formation and stability of gelatin gels. Moreover, the melting temperature of polymer gels with different salt addition conforms to the following orders: Na<SUP>+</SUP><Ca<SUP>2+</SUP><Cr<SUP>3+</SUP>. The different trend observed in respect of the storage modulus indicated that the triple helices dominated the gelatin gel strength, and the binding mechanism of Ca2+ may be different from that of Cr<SUP>3+</SUP>.
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