海藻酸钠在溶液中的尺寸和柔韧性

IF 2.8 4区 化学 Q3 POLYMER SCIENCE
Arnab Banerjee, Bidyut Debnath, Bijan Das
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引用次数: 0

摘要

研究了生物聚合物海藻酸钠在甲醇-水二元体系中的尺寸和柔韧性,通过粘度测量来探讨介质、离子强度和温度对该聚合物溶液行为的影响。特别地,采用几种不同介电常数的甲醇和水的混合物作为介质,并通过添加外盐(NaCl)来调节海藻酸钠溶液的离子强度。采用现象学方法测定了聚合物溶液的固有粘度。当添加盐的浓度增加时,从广义特性粘度和旋转值的均方根半径可以看出,多极化线圈的尺寸急剧减小。相对于无盐溶液中拉伸最大的构象,θ-条件下的旋转半径(由特征粘度的s型拟合基值与添加盐块的对数浓度的拟合得到)在298.15 K和308.15 K时分别减小了近65%和63%,与水相中的旋转半径(分别为47%和51%)相比,这是相当大的。在研究的温度下,藻酸盐链在大约6-7个单体的长度上保持刚性,表明这种碳水化合物聚合物在甲醇-水介质中具有半柔性性质。在最低盐添加量(0.1 mmol·L−1)的溶液中,静电对持续长度的贡献约为固有持续长度的80-90倍,表明在低盐溶液中有明显的链延伸。考虑到链上涉及两个单体单元和溶剂分子的内环的形成和破坏,可以解释链尺寸随混合溶剂介质组成的变化。本研究还批判性地评估了介电常数、反离子脱溶和解离对链尺寸温度依赖性的相对贡献。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Dimension and flexibility of sodium alginate in solution

The dimension and the flexibility of a biopolymer sodium alginate have been investigated in methanol-water binaries to explore the effects of medium, ionic strength, and temperature on the solution behavior of this polymer from viscosity measurement. In particular, several mixtures of methanol and water with varying dielectric constants were used as the media, and the ionic strength of the sodium alginate solutions was adjusted by adding an external salt (NaCl). A phenomenological approach was applied for the determination of the intrinsic viscosities of the polymer solutions. There has been a drastic reduction in the polyion coil size as manifested by the generalized intrinsic viscosity as well as by the root mean square radii of gyration values when the concentration of the added salt is increased. With respect to the maximally stretched conformation in salt-free solutions, the radius of gyration under θ-condition (obtained from the base values of the sigmoidal fits of the intrinsic viscosity vs. the logarithmic concentration of the added salt plots) decreases by nearly 65% and 63% at 298.15 and 308.15 K respectively, which is quite large compared to that in the aqueous phase (47% and 51% respectively). The alginate chains have been found to remain stiff over a length of about 6–7 monomers at the temperatures investigated, indicating a semi-flexible nature of this carbohydrate polymer in methanol-water media. The electrostatic contributions to the persistence length in the solution with the lowest amount of the added salt (0.1 mmol·L−1) shoot up to ca. 80–90 times the intrinsic persistence length indicating an appreciable chain extension in low-salt solutions. The variation of the chain dimensions with the composition of the mixed solvent media has been interpreted considering the formation and disruption of internal rings involving two monomeric units on the chain and solvent molecules. This study also assessed critically the relative contributions of the dielectric constant, counterion desolvation and dissociation to the temperature-dependence of the chain dimension.

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来源期刊
Journal of Polymer Research
Journal of Polymer Research 化学-高分子科学
CiteScore
4.70
自引率
7.10%
发文量
472
审稿时长
3.6 months
期刊介绍: Journal of Polymer Research provides a forum for the prompt publication of articles concerning the fundamental and applied research of polymers. Its great feature lies in the diversity of content which it encompasses, drawing together results from all aspects of polymer science and technology. As polymer research is rapidly growing around the globe, the aim of this journal is to establish itself as a significant information tool not only for the international polymer researchers in academia but also for those working in industry. The scope of the journal covers a wide range of the highly interdisciplinary field of polymer science and technology, including: polymer synthesis; polymer reactions; polymerization kinetics; polymer physics; morphology; structure-property relationships; polymer analysis and characterization; physical and mechanical properties; electrical and optical properties; polymer processing and rheology; application of polymers; supramolecular science of polymers; polymer composites.
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