Polyelectrolyte microstructure in chitosan aqueous and alcohol solutions.
Polyelectrolyte microstructure in chitosan aqueous and alcohol solutions.
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DOI：
10.1021/bm060911m
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发表时间：
2007-03
影响因子：
6.2
通讯作者：
N. Boucard;L. David;C. Rochas;A. Montembault;C. Viton;A. Domard
中科院分区：
文献类型：
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作者：
N. Boucard;L. David;C. Rochas;A. Montembault;C. Viton;A. Domard
本文研究了壳聚糖水溶液和水醇溶液中的链序。用小角度同步加速器x射线散射研究了所谓的多电解质峰。聚电解质的微观结构表征是聚电解质散射峰的最大值qmax的位置，它与聚合物浓度cp成比例，qmax近似于cp α。幂律指数α随壳聚糖乙酰化程度（DA）的变化而变化，这是导致电荷密度(f)和聚合物链疏水性变化的原因。结果突出了多勃雷宁和鲁宾斯坦理论的两种组织体系，这是首次在天然聚合物中进行研究。在低DAs时，alpha约为1/2，与珍珠项链组织一致，珍珠项链的结构由珍珠之间的串珠控制。对于较高的DA， alpha约为1/3，聚电解质峰显示的相关性受珍珠控制。该分析提供了一种定量研究在天然聚合物溶液性质中起重要作用的疏溶剂-亲溶剂相互作用之间平衡的方法。此外，还证明了几个参数对相互作用平衡的作用，如反离子的性质、溶剂的组成（水溶液中酒精的量）和盐的加入对库仑力的屏蔽作用。最后，讨论了从聚电解质溶液到物理凝胶的纳米结构转变。当疏溶剂相互作用有利时，聚电解质达到凝胶状态，但根据凝胶化途径的不同，聚电解质的有序性可以保持或不保持。
This work deals with chain ordering in aqueous and water-alcohol solutions of chitosan. The so-called polyelectrolyte peak is investigated by small-angle synchrotron X-ray scattering. The polyelectrolyte microstructure was characterized by the position of the maximum of the polyelectrolyte scattering peak qmax, which scales with the polymer concentration cp as qmax approximately cp alpha. An evolution of the power law exponent alpha is observed as a function of the degree of acetylation (DA) of chitosan, which is responsible for changes of both the charge density (f) and the hydrophobicity of the polymer chains. The results highlighted the two organization regimes of the theory of Dobrynin and Rubinstein, investigated here for the first time for a natural polymer. At low DAs, alpha approximately 1/2, in agreement with a pearl necklace organization where the structure is controlled by the string between pearls. For higher DA, alpha approximately 1/3, and the correlation revealed by the polyelectrolyte peak is controlled by the pearls. This analysis offers a way to study quantitatively the balance between solvophobic-solvophilic interactions that play an important role in the solution properties of natural polymers. In addition, the role of several parameters acting on the interaction balance were evidenced, such as the nature of the counterion, the composition of the solvent (amount of alcohol in the aqueous solution), and the screening of Coulombic forces by salt addition. Finally, the nanostructure transition from a polyelectrolyte solution to a physical gel is discussed. The gel state is reached when the solvophobic interactions are favored, but depending on the gelation route the polyelectrolyte ordering could be preserved or not.