Covalent Cross-Linked Polymer Gels with Reversible Sol-Gel Transition and Self-Healing Properties
Covalent Cross-Linked Polymer Gels with Reversible Sol-Gel Transition and Self-Healing Properties
复制标题
具有可逆溶胶-凝胶转变和自修复特性的共价交联聚合物凝胶
DOI：
10.1021/ma9022197
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发表时间：
2010-02-09
期刊：
影响因子：
5.5
通讯作者：
Chen, Yongming
中科院分区：
文献类型：
--
作者：
Deng, Guohua;Tang, Chuanmei;Chen, Yongming
导论.共价和可逆的非共价相互作用是聚合物凝胶形成三维网络的两种基本交联力。因此，聚合物凝胶可分别定义为化学凝胶或物理凝胶。1r3化学凝胶中基于共价键的网络在环境条件下是稳定的，这是由于它们的共价键的稳健性和不可逆性。虽然化学凝胶可以通过响应刺激而溶胀或去溶胀其永久网络来显著改变其体积，但它不能转化为其起始聚合物（单体）溶液。相比之下，基于物理凝胶中非共价相互作用的超分子网络对外部环境敏感。物理凝胶很容易响应于温度、pH和溶剂进行溶胶-凝胶转变。7，8从这个意义上说，物理凝胶比化学凝胶更聪明。将物理凝胶的刺激响应性和化学凝胶的稳定性整合到一个单一的体系中以产生一种坚固而智能的凝胶仍然是一个挑战。动态共价化学为构建这种材料提供了一个诱人的前景。它采用可逆共价键而不是非共价相互作用来制备产物。通过调节涉及这种可逆共价键的热力学控制的反应，可以调节产物的分布或构成及其性质。因此，产物作为超分子实体响应于外部刺激是智能的，但由于可逆共价键的强性质，它们比超分子更稳定。10r12作为动态共价键的一种，Lehn等人成功地利用酰腙键制备了动态共价聚合物。聚酰腙，所谓的动力剂，10，11可以与外部单体交换它们的组分，并将它们掺入原始聚合物中。13，14利用这种交换，可以改变原始发电机的机械性能15或颜色和荧光16。最近，由同一组报道了带有侧糖部分的糖基动力剂。17所有这些动力剂都是线性或支化的，然而，基于酰腙键的交联网络及其在凝胶中的动力学性质迄今尚未报道。
Introduction. Covalent and reversible noncovalent interactions are two basic cross-linking forces to form threedimensional networks in polymer gels. Accordingly, polymer gels can be defined as chemical gels or physical gels, respectively. 1r3 The networks based on covalent bonds in chemical gels are stable under ambient conditions owing to their robust and irreversible natures of the covalent bonds. Although a chemical gel can dramatically change its volume by swelling or deswelling its permanent network in response to stimuli, it cannot be transformed into its starting polymer (monomer) solution. 4r6 In contrast, the supramolecular networks based on noncovalent interactions in physical gels are susceptible to the external environment. It is easy for a physical gel to perform a solrgel transition in response to temperature, pH and solvent. 7, 8 In this sense, a physical gel is smarter than a chemical gel. Integrating the stimuli-responsibility of the physical gels and stability of the chemical gels into a single system to yield a robust but smart gel is still a challenge.Dynamic covalent chemistry9 offers an appealing prospect of constructing such materials. It employs reversible covalent bonds instead of noncovalent interactions to prepare products. By adjusting the thermodynamic controlled reactions involving such reversible covalent bonds, distribution or constitution of the products and their properties can be tuned. Consequently, the products are smart as supramolecular entities in response to external stimuli, but they are more stable than the supramolecular ones due to the strong nature of the reversible covalent bonds. 10r12 As one of the dynamic covalent bonds, acylhydrazone bond has been successfully used by Lehn and co-workers to prepare dynamic covalent polymers. Polyacylhydrazones, the so-called dynamers, 10, 11 could exchange their components with outside monomers and incorporated them into the original polymers. 13, 14 Taking advantage of this exchange, the mechanical properties15 or the color and fluorescence16 of the original dynamers can be modified. Very recently, glycodynamers bearing side saccharide moieties were reported by the same group. 17 All these dynamers were linear or branched, however, cross-linked networks based on acylhydrazone bonds and their dynamic properties in a gel have not been reported so far.