聚电解质链在中等受限凝胶网络中的“受挫”动力学  

Dynamics of Charged Macromolecules Under Confinement

作　　者：贾迪 Murugappan Muthukumar Di Jia;Murugappan Muthukumar(Beijing National Laboratory for Molecular Sciences,State Key Laboratory of Polymer Physics and Chemistry,Institute of Chemistry,Chinese Academy of Sciences,Beijing 100190;University of Chinese Academy of Sciences,Beijing 100049;Department of Polymer Science and Engineering,University of Massachusetts,Amherst,Massachusetts 01003)

机构地区：[1]中国科学院化学研究所北京分子科学国家研究中心、高分子物理与化学国家重点实验室,北京100190 [2]中国科学院大学,北京100049 [3]Department of Polymer Science and Engineering,University of Massachusetts,Amherst,Massachusetts 01003

出　　处：《高分子学报》2023年第2期151-165,共15页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号22273114)资助项目。

摘　　要：带电大分子在拥堵受限水环境中的运动对于许多生命过程以及生物大分子的运输与功能至关重要.以往人们认为处于受限环境下的高分子链都能进行自由扩散运动,且遵从爱因斯坦扩散方程.即使在最强烈的受限环境下,高分子链仍能进行一维无规扩散运动,其动力学符合管道模型.我们通过实验结合理论,设计凝胶网络尺寸与高分子链尺寸的比例来调控分子链受限环境的强弱,首次发现了大分子在中等受限环境下违背了爱因斯坦扩散方程,高分子整链是不能自由扩散运动的,但是一条链内的局部链段可以在每个凝胶网格内做多级局部松弛运动.其本质是高分子整链的质心运动需要其同时克服多个熵垒,从而实现一条高分子链在所有熵阱内的链段可以同时朝着一个方向做协同运动,而这在实验的观测时间尺度内几乎是不可能实现的,因此高分子链就被“困住”,形成一种能长期存在的非扩散型的亚稳态,我们将这一新型动力学定义为非扩散型拓扑动力学.本文首先对“受限环境”——带电水凝胶的物理性质进行介绍,第二部分介绍了带电大分子在浓溶液中的耦合动力学,最后介绍带电大分子在受限环境下的非扩散型拓扑动力学,包括由熵驱动的和由焓驱动的非扩散型动力学.Movement of large electrically charged macromolecules trapped inside spatially restrictive aqueous media is a ubiquitous phenomenon,underlying many natural living processes and technologies focused on separation science and controllable delivery of macromolecular cargos.In this broad context of general significance,we have developed a conceptual framework towards a fundamental understanding of the molecular mechanisms of how large macromolecules move around in crowded environments.Our conceptual development,based on a combination of experiments and theory,addresses the confluence of conformational fluctuations of the guest charged macromolecule being trapped and the host charged matrix(modelled using a hydrogel),structure and charge decoration of the host,long-ranged electrostatic interactions and van der Waals-type interactions in the composite system,and self-consistent coupling of the dynamics of all moving components(small electrolyte ions and large macroions)in the system.These advances are summarized in this review.Briefly,there are three components,each with tantalizing results.First,the dynamics of elasticity of the host charged gel are quantified in terms of shear modulus and bulk modulus,using dynamic light scattering measurements and modified Flory-Dusek-Patterson-Tanaka theory by accounting for electrostatics.Second,we show that a dilute solution of charged macromolecules exhibits the“ordinary-extraordinary transition”in the cooperative diffusion coefficient of the macromolecule.In the“ordinary”mode,the diffusion coefficient of a very large macromolecule can be as high as that of a small metallic ion.We attribute this strange effect to the coupling of the dynamics of the charged macromolecule and that of its dissociated counterions.The“extraordinary”mode arises from clustering of identically charged macromolecules induced by dipolar forces from ion-pairs formed by condensed counterions on the macromolecules.In the presence of added small molecular electrolyte,we find that an additional mod

关 键 词：聚电解质 非扩散性拓扑动力学 熵位垒 受限环境 带电凝胶网络 

分 类 号：O631.12[理学—高分子化学] O648.17[理学—化学]