Viscoelastic properties of chitosan solutions:: Effect of concentration and ionic strength
Viscoelastic properties of chitosan solutions:: Effect of concentration and ionic strength
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DOI：
10.1016/j.jfoodeng.2005.01.047
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发表时间：
2006-06-01
影响因子：
5.5
通讯作者：
Carreau, PJ
中科院分区：
文献类型：
--
作者：
Cho, JY;Heuzey, MC;Carreau, PJ
研究了壳聚糖溶液的动态流变性，考察了缠结体系的离子强度和壳聚糖浓度。首次确定了重叠浓度C*和纠缠浓度C-e来区分稀疏、半稀疏和浓缩纠缠态。在稀溶液中，离子强度(1)对特性粘度([n])的影响可用德拜静电屏蔽长度来解释。壳聚糖链的特性粘度、回转半径和持续长度随离子强度的增加而减小，这是因为盐屏蔽了壳聚糖链上的静电电荷，从而增加了链的柔韧性。对于浓溶液，进行了动态测量，并根据线性粘弹性区表征的存储(G‘)和损耗(G“)模数计算了弛豫谱。对于所有的壳聚糖浓度和离子强度，时间加权应力松弛谱只显示一个峰。然而，随着聚合物浓度的增加，光谱的宽度增加，这表明由于更多的纠缠和链间相互作用，弛豫模的分布更大。平均松弛时间(tau(H))和零剪切粘度(eta(0))分别与壳聚糖浓度呈幂函数关系，其中tau(H)与C-3.1相近，eta(0)与C-4.1相似，高指数反映了聚合物的缔合特性。壳聚糖溶液的非牛顿性(弹性和剪切稀化行为)随着壳聚糖浓度的增加和离子强度的降低而增加。(C)2005爱思唯尔有限公司。保留所有权利。
The dynamic rheological properties of chitosan solutions have been investigated in terms of ionic strength and chitosan concentration for entangled systems. The overlap concentration C* and the entanglement concentration C-e have first been determined to identify the dilute, semi-dilute and concentrated entangled regimes. In dilute solutions, the effect of ionic strength (1) on the intrinsic viscosity ([n]) has been interpreted in terms of the Debye electrostatic screening length. The intrinsic viscosity, the radius of gyration and the persistence length decreased with increasing ionic strength, due to the screening of the electrostatic charges on the chitosan chains by the salt resulting in increased chain flexibility. For concentrated solutions, dynamic measurements were performed and the relaxation spectra were calculated from the storage (G') and loss (G") moduli characterized in the linear viscoelastic region. For all chitosan concentrations and ionic strengths, the time-weighted stress relaxation spectra showed only one peak. However, the width of the spectra increased with increasing polymer concentration, indicating a larger distribution of relaxation modes due to more entanglements and interchain interactions. The mean relaxation time (tau(H)), related to reptation, and the zero-shear viscosity (eta(0)) were found to follow power-law expressions of the chitosan concentration, with tau(H) similar to C-3.1 and eta(0) similar to C-4.1, respectively, with the high exponents indicating the associating character of the polymer. The non-Newtonian nature (elastic properties and shear-thinning behavior) of the chitosan solutions increased with increasing chitosan concentration and decreasing ionic strength. (c) 2005 Elsevier Ltd. All rights reserved.