The effect of dynamic cross-links and mesogenic groups on the swelling and collapse of polymer gels

IF 5.4 1区 化学 Q2 CHEMISTRY, MULTIDISCIPLINARY
GIANT Pub Date : 2024-09-10 DOI:10.1016/j.giant.2024.100341
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引用次数: 0

Abstract

The polymer gels containing dynamic cross-links and mesogenic groups are among the key candidates for the development of soft actuators and detectors, displays, sensors and other programmable and self-healing materials. In this article, firstly, the collapse of polymer networks with irreversible cross-links in the presence of a dynamic cross-linker is investigated by means of Flory-type theory. It is shown that, at not a very poor solvent quality (near the theta-conditions), the swelling ratio for a gel containing irreversible and dynamic cross-links is less than for a gel with irreversible cross-links only, whereas at poor or good solvent qualities sizes of these gels are close to each other. The number of dynamic cross-links monotonically increases with worsening the solvent quality. The gel contraction can be also achieved by increasing the dynamic cross-linker concentration, which allows one to change the transition point in a wide range of solvent conditions. Secondly, polymer networks containing irreversible and dynamic cross-links and incorporating mesogenic side groups is studied using the Maier–Saupe theory. With decreasing in the temperature, the continuous transition from a swollen to collapsed state occurs. With further increase in the temperature, the swelling ratio discontinuously decreases and the nematic order parameter sharply increases from zero to a value ​​close to one. By increasing the dynamic cross-linker concentration, the swelling-to-collapse transition and, then, the isotropic-nematic transition are observed. A phase diagram of the gel is constructed and, depending on the dynamic cross-linker concentration and temperature, the swollen gel with the zero nematic order parameter, the collapsed gel with the zero nematic order parameter, and the collapsed gel with the nematic ordering can be formed. A growth of the length of the mesogenic side group leads to an increase in the area of ​​existence of the collapsed gel with the nematic ordering in the phase diagram. The obtained theoretical results are in agreement with corresponding experimental data from the literature.

Abstract Image

动态交联和介原基团对聚合物凝胶溶胀和崩解的影响
含有动态交联和介原基团的聚合物凝胶是开发软致动器和探测器、显示器、传感器以及其他可编程和自修复材料的主要候选材料之一。本文首先通过弗洛里型理论研究了具有不可逆交联的聚合物网络在动态交联剂存在时的塌缩。研究表明,在溶剂质量不是很差的情况下(接近θ条件),含有不可逆交联和动态交联的凝胶的溶胀率小于仅含有不可逆交联的凝胶,而在溶剂质量较差或较好的情况下,这些凝胶的尺寸则相互接近。动态交联的数量随着溶剂质量的恶化而单调增加。增加动态交联剂的浓度也可以实现凝胶收缩,从而在多种溶剂条件下改变过渡点。其次,我们利用 Maier-Saupe 理论研究了含有不可逆动态交联和介源侧基的聚合物网络。随着温度的降低,出现了从膨胀状态到塌缩状态的连续转变。随着温度的进一步升高,膨胀率不连续地降低,向列有序参数从零急剧上升到接近于 1 的值。通过增加动态交联剂浓度,可以观察到从膨胀到塌陷的转变,然后是各向同性-向列转变。根据动态交联剂浓度和温度的不同,可以形成向列有序参数为零的膨胀凝胶、向列有序参数为零的塌缩凝胶和向列有序的塌缩凝胶。介生侧基长度的增加会导致相图中存在向列有序塌缩凝胶的区域增大。获得的理论结果与文献中的相应实验数据一致。
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来源期刊
GIANT
GIANT Multiple-
CiteScore
8.50
自引率
8.60%
发文量
46
审稿时长
42 days
期刊介绍: Giant is an interdisciplinary title focusing on fundamental and applied macromolecular science spanning all chemistry, physics, biology, and materials aspects of the field in the broadest sense. Key areas covered include macromolecular chemistry, supramolecular assembly, multiscale and multifunctional materials, organic-inorganic hybrid materials, biophysics, biomimetics and surface science. Core topics range from developments in synthesis, characterisation and assembly towards creating uniformly sized precision macromolecules with tailored properties, to the design and assembly of nanostructured materials in multiple dimensions, and further to the study of smart or living designer materials with tuneable multiscale properties.
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