Belousov-Zhabotinsky反应驱动的智能高分子材料:拓扑结构及仿生功能

化学自振荡反应驱动的智能高分子材料常被称为自振荡高分子材料(self-oscillating polymer materials, SOPMs),其中以Belousov-Zhabotinsky(BZ)反应驱动的SOPMs研究最为深入,为高分子材料领域的一大研究热点。与传统智能高分子材料不同,SOPMs体系具有高度的自调节性,即可以不需要外界“开-关”转换的刺激就能自动、可逆、周期性地发生状态转变。本文结合SOPMs的最新研究结果,介绍该类材料在新型拓扑结构设计和仿生功能研究两个方面的新思想和新方法。在拓扑结构设计方面,主要介绍梳形自振荡高分子凝胶、“聚轮烷”互锁自振荡高分子凝胶、多级结构自振荡高分子凝胶、超级交联自振荡高分子凝胶、支化自振荡高分子、自振荡高分子刷以及嵌段自振荡高分子材料。在仿生功能研究方面,主要阐述自振荡高分子囊泡、人工细胞、自主肠状运动、趋光避光运动。最后,对SOPMs今后的发展作了展望。     

化学振荡反应调控的动态可逆智能体系

动态可逆作用是构筑智能材料体系,实现材料性能可控、可调性的重要工具。但是,多数基于动态可逆作用的智能体系仅能对"开/关"转换的外界刺激因素,如光、热、溶剂、pH等产生响应,不能实现自动调控。化学振荡反应及自振荡高分子材料的发展为新型自调控智能体系的构建提供了重要的思路。本文结合自调控智能体系的最新研究进展,介绍化学振荡反应调控的动态可逆智能体系(DRIS),包括利用动态共价键、主-客体作用、配位作用、离子作用、分子间作用等动态可逆作用构筑的纳米粒子自动聚集/分散体系、两亲性分子自组装/解组装体系、宏观凝胶自组装/解组装体系、自动分子器件、自动荧光振荡体系等。最后,对化学振荡反应调控的动态可逆智能体系的研究与发展进行展望。     

智能化自振荡高分子凝胶

自振荡高分子凝胶是一种智能化软物质材料,其体积无需外界刺激即能自发膨胀收缩,实现化学能向机械能转化,具有良好的研究和应用前景。本文介绍了自振荡凝胶的设计和自振荡机理、不同尺度的自振荡行为,以及温度、浓度、胶结构和外界刺激等因素对自振荡行为的影响等内容。从凝胶自驱动运动和物质运输两方面介绍仿生驱动凝胶在组织工程、生命科学、药物缓释和材料等领域的潜在应用,并展望了自振荡凝胶未来研究趋势。     

光敏性BZ反应的时空动力学

作为研究非线性时空动力学最理想的化学反应体系之一,三联(2,2'-联吡啶)钌(Ⅱ)(Ru(bpy)₃²⁺)为催化剂的Belousov-Zhabotinsky (BZ)振荡反应具有独特的光敏特性并能呈现丰富的时空动力学行为。研究光控BZ反应有助于我们对一系列物理、化学和生命体系中复杂动力学现象的理解。本文综述了不同实验条件下光效应对钌催化BZ反应均相复杂振荡和空间反应扩散化学波的影响, 以及光响应BZ反应与软物质耦合体系的复杂动力学行为,在此基础上介绍光抑制和光诱导反应机理和模型。对光控BZ反应体系存在的问题和发展方向进行了探讨。     

智能高分子表面的设计及其在生物医学中的应用

一般高分子材料表面对外界刺激反应性较弱，但利用一些化学或物理方法可提高其响应性，使其智能化。本文介绍了近年来智能高分子表面的几种设计思路、响应机理及其在生物医用材料方面的应用，并且提出了今后的发展趋势。     

响应性凝胶与非线性化学反应相互作用研究进展

本文综述了响应性凝胶与非线性反应动力学相互作用的研究进展,从实验及理论方面评述了pH振荡器中响应胶的振荡行为、P(NIPAAm-co-Ru(bpy)3)共聚凝胶中Belousov-Zhabotinsky(BZ)化学反应引起的膨胀-收缩振荡、行波和纳米制动器的制备及生理条件下凝胶自振荡行为,成为化学能向机械能转化的智能材料领域中活跃的研究方向; 同时凝胶的响应性作用于非线性化学反应可控制反应动力学的分岔行为.最后对该研究领域的发展方向和应用前景进行了展望.     

氨基酸对Belousov-Zhabotinskii反应的影响

作者研究了18种氨基酸及一种氨基酸酯的盐酸盐对 BZ 反应的影响。反应体系中以邻-菲罗啉亚铁离子为催化剂,其结果见英文表格。这19种氨基酸按其反应特点可以分为四类:(1)甘氨酸和其它烷基取代的天然氨基酸对 BZ 反应没有什么影响。(2)含硫元素的α-氨基酸使 BZ 反应的振荡周期加长,振幅加大,寿命变短。(3)具有吸电子基团取代的α-氨基酸使 BZ 反应的振荡周期缩短,振幅减少,寿命较短。(4)酪氨酸可加强 BZ 反应的振荡。甚至丙二酸不存在时也可进行化学振荡。作者还用不同的氨基酸代替丙二酸在 Mn~(++)和邻-菲罗啉亚铁离子的作用下研究 BZ 反应的化学振荡。上述(1)中的氨基酸、谷氨酸和赖氨酸均可发生5～6次的化学振荡。天冬氨酸和酪氨酸可以发生较长时间的振荡。其它氨基酸则不易发生振荡。     

以咖啡酸-KBrO3-H2SO4-Mn^2+为体系的化学振荡及其十字相图

本文报道的是一种新的BZ化学振荡反应。该反应是在酸性介质中,在锰离子催化下,咖啡酸被溴酸盐氧化所引起的化学振荡反应。就该体系在间歇反应器和连续流动体系中的振荡行为作了研究,得出了不同浓度、温度及流速下的特征振荡图形,计算出该振荡反应及其诱导期的活化能,并采用改变流速寻找双稳态的方法找出振荡的浓度区间,作出十字相     

以咖啡酸-KBrO3-H2SO4-Mn^2+为体系的化学振荡及其十字相图

本文报道的是一种新的 BZ 化学振荡反应.该反应是在酸性介质中,在锰离子催化下,咖啡酸被溴酸盐氧化所引起的化学振荡反应.就该体系在间歇反应器和连续流动体系中的振荡行为作了研究,得出了不同浓度、温度及流速下的特征振荡图形,计算出该振荡反应及其诱导期的活化能,并采用改变流速寻找双稳态的方法找出振荡的浓度区间,作出十字相图.     

间歇釜中BZ类均相无机振荡反应的研究

在间歇釜中, 以BrO3^--H2PO2^--Mn^2^+-Fe(phen)3^2^+-H2SO4为体系, 本文首次设计了一个纯无机均相BZ类化学振荡体系, 采用溴离子选择性电极和紫外可见分光光度计可分别观察到[Br^-],[Mn^3^+]和[Fe(phen)3^3^+]的振荡现象。对振荡反应产物及总反应计量关系进行了分析, 考察了反应物浓度和反应温度对体系振荡反应的影响, 并由此计算得到振荡反应的表观活化能, 研究了Cl^-,Br^-, Br2, 丙烯腈等因素对振荡反应的影响, 并由此对振荡反应的控制机理作了探索。对体系中两种金属离子的作用进行了分析。在此基础上提出了一种在间歇釜中设计均相BZ类振荡反应的新方法。利用这一方法, 不仅可以设计无机振荡反应, 而且还可以设计一系列由氨基酸、多肽、糖类等具有生物功能的物质参与的化学振荡, 有助于理解生物体内普遍存在的周期性现象。     

Dependence of turbidity oscillations of self-oscillating polymers on the selective recognition of the crown ether receptors contained in the polymer chain

The turbidity oscillations of self-oscillating polymers in the Belousov-Zhabotinsky (BZ) reaction system depending on the crown ether receptors contained in the polymer network have been studied. The three monomers are copolymerized, namely, N-isopropylacrylamide, the metal catalyst monomer for the BZ reaction, and the crown ether receptor monomer, to prepare the self-oscillating polymers used in this study. The turbidity oscillations are characterized by monitoring the transmittance of the polymer solution in the BZ reaction system at a specific wavelength of 570 nm. The oscillations are varied by crown ether receptors used in the polymerization process, i.e., BCAm(6) or BCAm(5), for the selective recognition of specific cations between potassium and sodium ions in the solution. The selective recognition of the BCAm receptors in the polymer chain for the two ions has brought out a variation in the turbidity oscillations by a change in the hydrophilicity of the polymer chain. The oscillations of the polymer solution composed of the BCAm(5) receptor are more influenced by sodium ion, while the polymer solution of BCAm(6) receptor is affected by potassium ion. However, the oscillation patterns of the redox changes obtained by these solution systems look much alike despite the differences in the polymer chain by crown ether receptors and cations of bromate used for the BZ reaction.     

Self-oscillation of polymer chains with rhythmical soluble-insoluble changes

Self-oscillation of polymer chains in an aqueous solution has been achieved. The ruthenium catalyst for the Belousov-Zhabotinsky reaction was polymerized by using N-isopropylacrylamide and dissolved into the solution containing the BZ substrates. Periodical soluble-insoluble changes of the polymer chain were spontaneously induced by the BZ reaction. The conformational oscillations of the polymer were measured as the optical transmittance changes of the solution. This is the first report that rhythmical and reversible soluble-insoluble changes of polymer chains are realized under constant and homogeneous conditions. The transducing system from chemical energy of the BZ reaction to optical information has been constructed.     

Self-oscillating polymer gel as novel biomimetic materials exhibiting spatiotemporal structure

As a novel biomimetic polymer gel, we have been studying polymer gel with an autonomous self-oscillating function since it was firstly reported in 1996. For developing the polymer gels, we utilized an oscillating chemical reaction, called the Belousov?CZhabotinsky (BZ) reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. The self-oscillating polymer gel is composed of a poly(N-isopropylacrylamide) network in which the metal catalyst for the BZ reaction is covalently immobilized. Under the coexistence of the reactants, the polymer undergoes spontaneous swelling?Cdeswelling changes (in the case of gel) or cyclic soluble?Cinsoluble changes (in the case of uncross-linked polymer) without any on?Coff switching of external stimuli. Several kinds of functional material systems utilizing the self-oscillating polymer and gel such as biomimetic actuators, mass transport surface, etc. are expected. Here, these recent progress on the self-oscillating polymer and gels and the design of functional material systems are summarized.     

A viscosity self-oscillation of polymer solution induced by the Belousov-Zhabotinsky reaction under acid-free condition

We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.     

Theoretical and computational modeling of self-oscillating polymer gels

The authors model wave propagation in swollen, chemoresponsive polymer gels that are undergoing the oscillatory Belousov-Zhabotinsky (BZ) reaction. To carry out this study, they first modify the Oregonator model for BZ reactions in simple solutions to include the effect of the polymer on the reaction kinetics. They then describe the gel dynamics through the framework of the two-fluid model. The polymer-solvent interactions that are introduced through the BZ reaction are captured through a coupling term, which is added to the Flory-Huggins model for polymer-solvent mixtures. The resulting theoretical model is then used to develop the gel lattice spring model (gLSM), which is a computationally efficient approach for simulating large-scale, two-dimensional (2D) deformations and chemical reactions within a swollen polymer network. The 2D calculations allow the authors to probe not only volume changes but also changes in the sample's shape. Using the gLSM, they determine the pattern formation and shape changes in 2D rectangular BZ gels that are anchored to a solid wall. They demonstrate that the dynamic patterns depend on whether the gel is expanded or contracted near the wall, and on the sample's dimensions. Finally, they isolate a scenario where the detachment of the gel from the wall leads to macroscopic motion of the entire sample.     

A comparative study of temperature dependence of induction time and oscillatory frequency in polymer‐immobilized and free catalyst Belousov‐Zhabotinsky reactions

Environment‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgel particles with covalently bonded ruthenium(4‐vinyl‐4′‐methyl‐2,2′‐bipyridine) bis (2,2′‐bipyridine) [Ru(vmbipy)(bipy)₂] display periodic size changes when placed in Belousov‐Zhabotinsky (BZ) reaction substrates. The temperature dependency of the induction time and oscillatory frequency of the BZ reaction in this polymer‐immobilized catalyst system were compared to the bulk BZ reaction with the catalyst in the solution phase. Prolonged induction times are observed for the immobilized catalyst, compared with free catalyst, while little difference is observed on the oscillation frequency. The Arrhenius frequency factor calculated using the induction time for the immobilized catalyst BZ reaction is about seven times smaller than that for the free catalyst Ru(bipy) case. On the other hand, the Arrhenius frequency factors calculated using the oscillatory frequency are almost the same, showing similar reaction kinetics during the BZ oscillations. The tunability of the induction time using a polymer matrix, as we observed here, while maintaining similar oscillatory behavior, should provide a new dimension to control the self‐assembling of BZ active particles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 847–854, 2009     

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.     

Benzil Photoperoxidations in Polymer Films and Crosslinking by the Resultant Benzoyl Peroxides in Polystyrene and Other Polymers

Benzil (BZ) can be converted almost quantitatively to benzoyl peroxide (BP) in aerated polymer films upon irradiation at >400 nm (i.e., the long-wavelength edge of the n→π* absorption band of BZ, where BP does not absorb). Here, we summarize results for the photoperoxidation of BZ structures with molecular oxygen, principally in glassy polymer matrices. Some of the polymers are doped directly with BZ or its derivatives, and others, contain covalently attached BZ pendant groups from which BP groups are derived. While the decomposition of low-molecular-weight BP doped into polymer films (such as those of polystyrene (PS)) results in a net decrease in polymer molecular weight, thermal decomposition of pendant BP groups is an efficient method for chain crosslinking. Crosslinking of PS films doped with a molecule containing two covalently linked BZ or BP groups proceeds in a similar fashion. Free radicals from the covalently attached BP allow grafting of new monomers, as well. Additionally, the use of radiation filtered through masks has been used to create patterns of polymers on solid surfaces. Crosslinking of photodegradable poly(phenyl vinyl ketone) with BP structures obtained by photoperoxidation of BZ structures for the preparation of photodegradable polymer networks is described as well. In sum, the use of BZ and BP and their derivatives offers simple and convenient routes for modifying polymer chains and, especially, for crosslinking them. Specific applications of each use and process are provided. Although applications with PS are featured here, the methodologies described are amenable to a wide variety of other polymers.     

Characterization of a self‐oscillating polymer with periodic soluble‐insoluble changes

A copolymer of N‐isopropylacrylamide (NIPAAm), ruthenium‐complex (Ru(bpy)₃), and N‐succinimidyl acrylic acid (NAS) was synthesized to investigate its selfoscillating properties in a solution. This polymer exhibits selfoscillation in turbidity and viscosity synchronized via a Belousov–Zhabotinsky (BZ) reaction. The molecular size of the polymer during oscillation was investigated by dynamic light scattering and electrochemical measurements. Both molecular size and viscosity exhibited periodic changes during the BZ reaction. A simple mechanism accounting for such periodic changes was investigated by numerical calculations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1578–1588, 2007     

Pentanary cross-diffusion in water-in-oil microemulsions loaded with two components of the Belousov-Zhabotinsky reaction

We measure cross-diffusion coefficients in a five-component system, an aerosol OT (AOT) water-in-oil microemulsion loaded with two constituents of the Belousov-Zhabotinsky (BZ) reaction (H(2) O/AOT/BZ1/BZ2/octane). The species BZ1 is either NaBr, an inhibitor of the BZ reaction, or ferroin, a catalyst for the reaction. As species BZ2, we choose Br(2) , an intermediate in the reaction. The cross-diffusion coefficients between BZ1 and BZ2 are found to be negative, which can be understood in terms of complexation between these species. Using a four-variable model for the BZ reaction, we find that the cross-diffusion coefficients measured here can lead to a noticeable shift in the onset of Turing instability in the BZ-AOT system.