Self-oscillation of polymer and photo-regulation by introducing photochromic site to induce LCST changes

We have developed polymers and gels with autonomous self-oscillating function by utilizing the Belousov–Zhabotinsky (BZ) reaction. The self-oscillating polymer is composed of poly(N-isopropylacrylamide), in which ruthenium tris(2,2′-bipyridine) is copolymerized as a catalyst for the BZ reaction. Under the coexistence of the reactants, the polymer undergoes spontaneous cyclic soluble–insoluble changes or swelling–deswelling changes (in the case of gel) without any on–off switching of external stimuli. In this study, spirobenzopyran was introduced into the self-oscillating polymer as the photochromic site. Under acidic condition necessary for the BZ reaction, photochromism of the spirobenzopyran occurs and the lower critical solution temperature of the polymer solution shifts to lower temperature with isomerization by photo-irradiation. As a result, on–off switching of the soluble–insoluble self-oscillation for the polymer solution is possible by photo-irradiation.     

pH‐reversible magnetic gel with a biodegradable polymer

Polymer gels that react to external stimuli, such as pH, temperature, and electromagnetic fields, are an important class of materials. Such materials have pharmaceutical, industrial, and biomedical applications. Our intention in this study was to synthesize a stimuli‐responsive polymer gel with a biodegradable polymer. However, the chemical crosslinker, divinyl sulfone, which is most widely used for the crosslinking of this type of material, is highly toxic in nature. To overcome this problem, a reversible magnetic gel was synthesized with hydroxy propyl cellulose (HPC) and maghemite at pH 13 without with a chemical crosslinker. With a decrease in pH from 13 to 9, the gel formed a homogeneous dispersion of HPC particles with maghemite in it. This process was a reversible physical gelation where the crosslinks of the network had a physical origin (in this case, hydrogen bonding) and, therefore, were sensitive to variations in pH. When this physically prepared gel was compared with the chemically crosslinked one, no significant differences in structural properties were noted. At higher pH values, the gel was formed due to weak intermolecular hydrogen bonding, as observed by the broadening of the IR band in both the magnetic and nonmagnetic gels. Transmission electron micrographs also showed no significant difference in the gel morphology. Differential scanning calorimetry showed an increase in melting temperature for the gel sample compared to that of pure HPC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3337–3341, 2004     

Hydrogen Bonding Modules for Use in Supramolecular Polymers

Supramolecular polymer chemistry has emerged as a major research focus within polymer science, because of the potential to improve material properties, through the combination of noncovalent interactions and synthetic polymers. As a supramolecular handle, the most useful noncovalent interaction is hydrogen bonding, which has been used extensively, because of advantages such as synthetic accessibility, directionality, fidelity, and, most importantly, responsiveness to external stimuli. This review introduces recent advances in the development of hydrogen bonding modules that can be useful for creating a variety of supramolecular polymers. Furthermore, we present selected examples of hydrogen bonded supramolecular polymers from the literature, by dividing them into three categories: supramolecular polymers assembled from small molecules, and main-chain and side-chain supramolecular polymers.     

Phenylboronate-diol crosslinked polymer gels with reversible sol-gel transition

Covalent dynamic gels based on reversible phenylboronic acid-diol ester bonds were prepared by crosslinking of N,N-dimethylacrylamide-4-((4-vinylbenzyloxy)carbonyl)phenylboronic acid copolymer, poly(VPB-co-DMA), and poly(2,2-bis(hydroxymethyl)butyl acrylate) (PHBA) in several organic solvents at ambient temperature. These gels formed rapidly and revealed typical properties of chemical gels. Analysis of the composition-property relationships of these polymer gels, specifically considering the effects of pH, molar ratio of HBA to VPB units, and gelator concentrations on dynamic rheological properties, were performed. Additionally, the polymer gels can be switched into their starting polymer solutions by adjusting pH of the system. The reversible sol-gel phase transition can be performed for several cycles in a similar way of supramolecular gel. Moreover, the gel revealed interesting self-healing property which occurred autonomously without any outside intervention. Employing this dynamic character, it is possible to regenerate the used gel, and thus has the potential to perform in a range of dynamic or bioresponsive applications.     

Reversible mechanochemical systems based on stimuli-responsive polymers. I. Fundamental aspects

Polymer gels can be used to prepare mechanical systems that convert chemical free energy into mechanical work. These gels have characteristics that cause shape changes or generate tensile stress that can lead to mobility.

The polymer gel network can be produced by several physical and chemical methods. The principle of reversible contraction and dilatation is based on different mechanisms that depend on the type of stimuli applied.

The kinetics of gel swelling has been studied and understood as a combination of two consecutive processes: the collective diffusion and the relaxation process. The response time of gel depends on the thermodynamic quality of the solvent. Gels based on “intelligent” polymers have many interesting applications. Hence, these gels can form the basis of future “soft, wet” technology.     

Fabrication and applied investigation of a muscle‐like linear actuator using lonic polymer metal composites

Focusing on the existing issues of ionic polymer metal composites (IPMC), for example, little force output and swing motion, and the applied requirements in the biomimetic artificial muscles using as the actuators, under the current framework, a muscle‐like linear actuator based on the combination of Bi‐IPMC linear actuator unit, whose experimental characteristics have been discussed in our previous work, was fabricated. The performance investigation showed that it can generate a linear movement type like artificial muscle, and there is an prominent improvement of force output capabilities compared with Bi‐IPMC linear actuator unit. Also, based on the 3D printing technique, a bionic jumping robot was experimented using the fabricating muscle‐like linear actuator, and the experimental result was validated against the feasibility of muscle‐like linear actuator. POLYM. COMPOS., 38:147–156, 2017. © 2015 Society of Plastics Engineers     

液晶弹性体复合纤维材料在智能响应领域的研究进展

液晶弹性体（LCEs）是一种包含液晶基元轻度交联的聚合物网络,兼具聚合物网络的软弹性和液晶基元的各向异性。通过编程分子取向可使液晶弹性体在受到外界环境的刺激下实现非接触运动,表现出优异的弹性和驱动性能,在人工肌肉、软体机器人和可穿戴设备领域中显示了巨大的潜力。液晶弹性体纤维作为LCEs的一种常见存在形式,由于纤维内液晶基元取向度高,对于各类型刺激响应更为灵敏,且具有良好的可编程特性和优异的机械强度,使其在众多领域展现出广阔的应用前景。本文综述了液晶弹性体纤维的主要制备方法、分析了其对不同类型刺激的响应驱动机理,详细介绍了光响应型液晶弹性体的分类,并阐明了光热转换过程和远程驱动调控机制。此外,本文分析了不同驱动方式的液晶弹性体纤维体系,简要论述了纤维基LCEs复合材料在柔性传感、智能驱动、软体机器人、人工肌肉等方面的最新研究进展,并对其发展前景进行了展望。     

Quickly self-healing hydrogel at room temperature with high conductivity synthesized through simple free radical polymerization

The use of conductive self-healing hydrogels in electronic devices not only reduces replacement and maintenance costs but also prolongs their lifetime. Therefore, developing hydrogels with autonomous self-healing properties and electronic conductivity is vital for the advancement of emerging fields, such as conductors, semiconductors, sensors, artificial skin, and electrodes and solar cells. However, it remains a challenge to fabricate a hydrogel with high conductivity that can be healed quickly at room temperature without any external stimulus. In this work, we report an effective and simple free radical polymerization approach to synthesizing a hydrogel using modified rGO and acrylate monomers containing abundant ion groups. The hydrogel exhibits excellent electronic conductivity, extremely fast electronic self-healing ability, and excellent repeatable restoration performance at 25 °C. The conductivity of the hydrogel reaches 27.2 S/m, the hydrogel recovers its original shape, and scoring scratched on the surface totally disappears after holding at 25 °C for 40 s. This conductive, room-temperature self-healing hydrogel takes unique advantage of supramolecular chemistry and polymer nanoscience and has potential applications in various fields such as self-healing electronics, artificial skin, soft robotics, biomimetic prostheses, and energy storage. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47379.     

Dye-sensitized solar cells with quasi-solid-state cross-linked polymer electrolytes containing aluminum oxide

Cross-linked gel polymer electrolytes containing aluminum oxide nanoparticles are prepared by in situ chemical cross-linking after injection of the gel precursor into the dye-sensitized solar cell (DSSC). This makes it possible to directly solidify the electrolyte in the cell and maintain good interfacial contacts between the electrolyte and the electrodes without suffering loss of performance in the DSSC. These gel polymer electrolytes exhibit high ionic conductivity and favorable charge transfer reaction at the interfaces of electrodes and electrolyte. The quasi-solid-state DSSC assembled with optimized gel polymer electrolyte exhibited remarkably high conversion efficiency, 6.34% at 100 mW cm⁻², and better long-term stability, as compared to the DSSC with liquid electrolyte.     

Strategies toward development of biodegradable hydrogels for biomedical applications

ABSTRACT

Hydrogel is a macromolecular gel constructed of a network of cross-linked polymer chains. Hydrogels are class of materials that can be tuned toward the subjected stimuli and can be modified to imitate the extracellular environment of the body which makes hydrogel worthy of being used in tissue regeneration, drug delivery, and other fields of science. Hydrogels offer excellent potential as oral therapeutic systems due to inherent biocompatibility, and biodegradability. Hydrogels are having various tissue engineering and drug delivery application due to its high loading with ensured molecule efficacy, high encapsulation, variable release profile, stable, and inexpensive.     

Dynamics of polymers in solution and melts

Simple models of polymer dynamics are available in dilute solution, moderate concentrations and melts, since it is possible to make models of the motion in these cases. A series of power laws result which fit well with computer simulation. It is more difficult to derive these models directly from sensible equations of motion, but progress in this direction is reported in the paper.     

原位聚合制备有机累托石/聚甲基丙烯酸甲酯纳米复合凝胶聚合物电解质

通过自由基引发,以有机增塑剂为溶剂,用原位聚合的方式制备出有机累托石/聚甲基丙烯酸甲酯[organic-modified rectorite/poly(methyl methacrylate),OREC/PMMA]凝胶聚合物电解质(gel polymer electrolyte,GPE),研究了不同的分散工艺对纳米GPE(nano-GPE,NGPE)膜性能的影响.通过X射线衍射和透射电镜探讨NGPE的微观结构,并初步研究了NGPE膜的离子电导率(σ)和5%质量损失率对应的初始热分解温度(θi).结果表明:OREC片层精细呈解离状,良好地分散在凝胶体系中.随OREC添加质量(下同)的增加,NGPE的σ及θi均呈现先增大后减小的趋势.当OREC的添加量为5%时,具有较高的σ和θi.     

智能高分子材料

介绍了几种新型的智能高分子材料,指出合成新的聚合物、制造构造规则的高分子凝胶及增加材料的表面积与体积比是加快智能高分子材料响应速率的方法,同时指出仿生化和模糊化是智能高分子材料的发展方向。     

高吸水性树脂的结构设计与性能改善

利用Flory凝胶理论阐明了高吸水性树脂的吸水机理 ,并解释了高分子链上的电荷密度、外界溶液离子强度以及交联度对树脂吸水倍数和吸水速率的影响。介绍了利用分子设计和颗粒形状设计对高吸水性树脂进行结构设计以改善树脂综合性能的方法。指出今后高吸水性树脂的研究重点应集中在高性能化、材料复合化、智能性凝胶、生物可降解性的研究等几个方面     

Using light to control the interactions between self-rotating assemblies of active gels

Polymer gels undergoing the oscillating Belousov-Zhabotinsky (BZ) reaction exhibit an autonomous, periodic swelling and deswelling, where the mechanical oscillations are driven by the chemical reaction within the polymer network. Using computer simulations, we show that these BZ gels can undergo a form of auto-chemotaxis, enabling the gels to spontaneously move in response to self-generated chemical gradients. Focusing on four millimeter-sized pieces of these BZ gels, we show that the pieces can organize into self-rotating clusters that resemble a moving pinwheel or gear. By analyzing the factors that promote the formation of a single self-rotating cluster, we attempt to design systems of multiple, interacting gears. We show that light, which suppresses the oscillations of the gels, can be harnessed to promote the formation of two self-rotating clusters. These studies point to a novel form of photo-chemo-mechanical transduction, where light is utilized to control the conversion of chemical and mechanical energy in the system. Moreover, the interaction between the BZ gel gears reveals a new form of entrainment between these moving units. Namely, their coordinated motion is achieved through chemical coupling or communication, rather than a mechanical coupling. These findings can lead to the formation of chemically “communicating” devices that can be programmed to perform autonomous work through the use of light.     

聚合物凝胶堵漏剂的研究与应用进展

聚合物凝胶堵漏剂是近年来逐步完善和发展起来的一种堵漏材料。简要介绍了聚合物凝胶堵漏剂特点及作用机理,并对国内外聚合物凝胶堵漏剂的研究及应用进行了评述。聚合物凝胶堵漏剂包括地下交联聚合物凝胶和可吸水膨胀交联聚合物凝胶,交联聚合物凝胶强度较低,必须与其他刚性材料配合才能很好地发挥作用。在堵漏施工中,交联聚合物凝胶不受漏失通道的限制,能够通过挤压变形进入裂缝和孔洞空间,最终达到封堵漏层的目的。现场应用表明,聚合物凝胶堵漏剂与其他材料配合使用,能很好地解决钻井过程中的恶性漏失,堵漏成功率高,对碳酸盐岩、裂缝发育地层及孔洞漏失特别有效。     

聚合物压裂液在辽河油田低渗储层的应用

报道了一种聚合物增稠剂zcy-01和交联剂JL-01为基础配制的压裂液。增稠剂zcy-01是一种低分子量聚合物,溶解速度快,在水中完全时间小于20 min;增粘效果好,0.5%浓度的聚合物基液粘度可达63 MPa·s。在酸性条件(pH=5~6)下与酸性交联剂以100∶0.5比例混合形成可挑挂冻胶,该冻胶呈透明状,携砂稳定。该压裂液耐温性好,破胶效果好,残渣含量小于100 mg/L,防膨率达到80.36%,适合于压裂施工。在强1块两口井的压裂施工中,增产效果明显。     

环境刺激响应型高强度智能水凝胶研究进展

环境刺激响应型智能水凝胶能够对外界环境因素的变化产生显著的体积或其他特性的变化,且其性质和结构与生物组织类似,有望应用于人工软骨、人造肌肉、组织工程等领域,引起了广泛的关注。提高环境刺激响应型智能水凝胶的力学性能是智能水凝胶应用研究的重要方向之一。本文综述了近年来环境刺激响应型高强度智能水凝胶的研究进展,简述了高强度智能水凝胶的网络结构的构建策略与方法,分析了其具备高力学性能的机理,重点介绍了4类不同结构的高强度智能水凝胶,即超低交联结构水凝胶、纳米颗粒复合水凝胶、拓扑结构水凝胶以及双网络结构水凝胶,最后讨论了环境刺激响应型高强度智能水凝胶在面向应用的研究过程中仍然需要解决的关键科学问题,如智能水凝胶的环境刺激与力学性能的博弈效应以及响应环境刺激前后的力学性能差异等。     

原位构建富氟SEI的凝胶电解质用于金属锂二次电池

以六氟磷酸锂（LiPF₆）为四氢呋喃的聚合引发剂制备凝胶电解质,同时作为氟源在金属锂负极表面原位构建富含LiF的固态电解质界面层（solid electrolyte interface,SEI）来抑制锂枝晶的生长以及金属锂/电解液之间的副反应。所制备的凝胶电解质具有较高的室温离子电导率（1.33 mS·cm^-1）和较宽的电化学稳定窗口（4.5 V）。原位聚合方式组装金属锂对称电池循环后,锂负极表面没有明显的锂枝晶和被损毁的形貌出现;XPS结果表明锂负极表面生成了富含LiF的SEI。组装的LiFePO₄全电池在1 C的电流密度下,稳定循环400周后仍保持118.7 mAh·g^-1的放电比容量。得益于四氢呋喃在开环聚合反应过程中,促进了LiPF₆分解反应平衡的正向移动,在锂负极表面形成稳定的富含LiF的SEI,能够抑制锂枝晶的生长并防止其被持续性的腐蚀破坏。     

聚甲基丙烯酸羟乙酯/乙二醛交联体系的溶液-凝胶-溶液转变研究

聚合物凝胶的溶液-凝胶（sol-gel）/凝胶-溶液（gel-sol）转变通常依赖于外界条件（温度、pH等）的变化，但构建可在恒定条件下实现sol-gel-sol转变的凝胶体系依然是一个挑战。本文基于聚甲基丙烯酸羟乙酯（PHEMA）、乙二醛（GX）和N,N-二甲基甲酰胺（DMF）成功构建了一种恒温自发随时间进行sol-gel-sol转变的聚合物凝胶体系（HGX）。通过改变GX的含量、温度等条件，可对HGX的成胶时间、凝胶强度及降解时间进行调控。结果表明，不同条件下HGX可在10~1500 min内形成弹性模量可达847 Pa的凝胶，然后在1.5 h到＞15 d后降解为低粘液体（＜30 mPa·s）。并利用红外光谱和凝胶色谱揭示了sol-gel-sol转变的内在机理是缩醛反应和酯基断键的动态竞争所致。