Gelation mechanism of κ- and ι-carrageenan investigated by correlation between the strain-optical coefficient and the dynamic shear modulus
Gelation mechanism of κ- and ι-carrageenan investigated by correlation between the strain-optical coefficient and the dynamic shear modulus
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DOI：
10.1021/ma0102924
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发表时间：
2001-10-09
期刊：
影响因子：
5.5
通讯作者：
Date, M
中科院分区：
文献类型：
--
作者：
Takemasa, M;Chiba, A;Date, M
测量了Kappa-卡拉胶和L-卡拉胶水溶液的动态剪切模量、应变光学系数和光学透过率随温度和频率的变化规律，以阐明凝胶形成的机理。根据剪切模量与应变光学系数之间的关系，讨论了凝胶网络的生长以及阳离子物种(K、Cs、Ca)和KCl量的影响。对于所有样品，这些关联可以用凝胶状态下低温区的幂函数来描述。该指数可以解释为反映凝胶网络生长过程的特征参数。根据指数的值，我们发现了两组。对于质量分数为2.0wt%(高聚合物浓度)的K型和Cs型卡拉胶，指数远大于1，而对于1.0wt%(低聚合物浓度)K型和2.0wt%K型t-卡拉胶，则接近于1。对于前一组，诱导单位取向所需的应力随着温度的降低而增加，而对于后一组，随着温度的降低，其增加幅度不大。也就是说，只有前者在凝胶网络的生长过程中，交联区内部的结构发生了显著的变化。我们的结论是，凝胶生长过程中聚集的螺旋分子数量的增加方案强烈依赖于阳离子种类和卡拉胶类型。
The temperature and frequency dependence of the dynamic shear modulus, strain-optical coefficient, and the optical transmission of kappa- and l-carrageenan aqueous solutions were measured in order to clarify the gelation mechanism. The growing of the gel net-work and the effect of cation species (K, Cs, and Ca) and the amount of added KCl are discussed on the basis of the correlation between the shear modulus and strain-optical coefficient. For all samples, these correlations can be described by a power function in the low-temperature region in the gel state. The exponent can be interpreted as a characteristic parameter reflecting the growing process of the gel network. We found two groups in terms of the value of the exponent. In the case of 2.0 wt % (high polymer concentration) K-form and Cs-form kappa -carrageenan, the exponent is much higher than unity, but in the case of 1.0 wt % K-form (low polymer concentration) kappa -carrageenan with added KCl and 2.0 wt % K-form t-carrageenan, it is close to unity. For the former group, the stress required to induce the unit orientation increases, while for the latter group it does not increase much with decreasing temperature. In other words, the structure inside cross-link region changes markedly during the growing process of gel network only for the former group. We concluded that increasing schemes of the number of aggregated helical molecules during the gel growing process strongly depends on the cation species and carrageenan type.