自修复高分子材料近五年的研究进展

自修复材料的概念源于对生物体自愈合现象的仿生研究,该类材料在受到损伤时可进行自修复并恢复一定程度的力学等性能。对高分子材料而言,其受机械力损伤后一般发生大分子链均裂或异裂而使材料产生微裂纹,此类微裂纹很难探测,而微裂纹的产生往往会引起高分子材料失效,因此快速修复微裂纹对诸多工程领域的高分子材料来讲尤为重要。本文从外源型及本征型自修复高分子材料两个方面,综述了近五年自修复高分子材料的研究进展,并对其今后发展进行了展望。     

Creation of a nanovascular network by electrospun sacrificial nanofibers for self-healing applications and its effect on the flexural properties of the bulk material

Composites, increasingly significant due to their excellent properties, are prone to failure over time. Self-healing materials are being developed to extend their lifetime. Despite continuous progress, the effect of introducing such healing feature on the mechanical properties of the neat material is mainly overlooked. Therefore, we created a nanocomposite and a nanovascular network by pullulan sacrificial nanofibers, and analysed the flexural properties in comparison to the neat matrix. A parameter analysis of the electrospinning process allowed production of tailored pullulan nanofibers. Their introduction showed no effect on the strength and modulus of the epoxy matrix. On removal of the pullulan nanofibers, the properties of the resultant nanovascularized epoxy were somewhat reduced relative to the neat epoxy depending on volume fraction and diameter of the nanochannels. Interestingly, the decrease of mechanical properties of the nanovascular epoxy is lower than by introducing microcapsules, and opens potential for a more appropriate introduction of self-healing systems in polymeric matrices.     

三聚氰胺-甲醛树脂包裹环氧树脂微胶囊的制备及表征

针对环氧树脂基材料的自修复,选取四氢邻苯二甲酸二缩水甘油酯作为芯材,采用三聚氰胺-甲醛树脂为壁材,对其进行微胶囊化包裹.结果表明,制得的具有单囊结构的环氧树脂微胶囊,胶囊粒径较小(约6.7μm)、囊壁较薄(约0.2μm)、芯含量较高(83.2 wt%),囊壁内、外表面光滑致密,胶囊具有良好的密闭性和耐热性;在微胶囊化过程中,三聚氰胺-甲醛树脂的缩聚反应动力学起关键作用,芯材没有参与囊壁形成的交联反应;包裹后的芯材活性保持不变,胶囊被复合到材料过程中囊芯活性也保持不变;胶囊的强度较高,能承受与基体材料复合过程中的外力作用,且与基体材料间粘结良好,在裂纹形成过程中能够随基体同时开裂.     

基于动态共价键的自愈性水凝胶及其在医学领域的应用

自愈性水凝胶作为一种新型仿生智能材料受到了科研人员的广泛关注.近年来,人们利用动态共价键、超分子作用,发展了一系列自愈性水凝胶,并将其应用于药物控释、细胞三维培养、组织工程等生物医用领域.本文总结和评述了基于动态共价键的自愈性水凝胶及这些水凝胶作为药物载体的相关研究,并展望了基于动态化学的自愈性水凝胶的未来发展.     

Synthesis and characterization of microencapsulated dicyclopentadiene with melamine–formaldehyde resins

Microcapsules containing healing agents have been used to develop the self-healing polymeric composites. These microcapsules must possess special properties such as appropriate strength and stability in surrounding medium. A new series of microcapsules containing dicyclopentadiene (DCPD) with melamine–formaldehyde (MF) resin as shell material were synthesized by in situ polymerization technology. These microcapsules may satisfy the requirements for self-healing polymeric composites. The chemical structure of microcapsule was identified by using Fourier transform infrared (FTIR) spectrometer. The morphology of microcapsule was observed by using optical microscope (OM) and scanning electron microscope. Size distribution and mean diameter of microcapsules were determined with OM. The thermal properties of microcapsules were investigated by using thermogravimetric analysis and differential scanning calorimetry. Additionally, the self-healing efficiency was evaluated. The results indicate that the poly(melamine–formaldehyde) (PMF) microcapsules containing DCPD have been synthesized successfully, and their mean diameters fall in the range of 65.2∼202.0 μm when the adjusting agitation rate varies from 150 to 500 rpm. Increasing the surfactant concentration can decrease the diameters of microcapsules. The prepared microcapsules are thermally stable up to 69 °C. The PMF microcapsules containing DCPD can be applied to polymeric composites to fabricate the self-healing composites.     

Stimuli-responsive polymeric materials functioning via host–guest interactions

Molecular recognition is essential for realizing functional supramolecular materials. Non-covalent host–guest interactions are an effective tool to introduce switching and functional properties into materials. This review focuses on the achievement of selective molecular adhesion, self-healing, toughness, and actuation properties. These functions have been achieved by reversible bond formation with cyclodextrins (CDs). Self-healing materials with host–guest interactions involving CDs have been used to achieve redox-responsive healing properties and healing efficiency. Furthermore, the materials, which undergo self-healing by chemical and physical mechanisms, exhibit rapid and efficient self-healing properties under semi-dry conditions. To prepare a supramolecular actuator using host–guest complexes, two approaches have been introduced. The first is the functionalization of a supramolecular gel actuator by changing the cross-linking density, and the second is the functionalization of a topological gel actuator by changing distances between the cross-linking points. Both actuators exhibit contractive bending behavior. This review summarizes advancements within the past 10 years in supramolecular materials that function via the chemical mechanism of host–guest interactions and the physical mechanism of the sliding motion of ring molecules.     

Functioning via host–guest interactions

Molecular recognition is essential for realizing functional supramolecular materials. Non-covalent host–guest interactions are an effective tool to introduce switching and functional properties into materials. This review focuses on the achievement of selective molecular adhesion, self-healing, toughness, and actuation properties. These functions have been achieved by reversible bond formation with cyclodextrins (CDs). Self-healing materials with host–guest interactions involving CDs have been used to achieve redox-responsive healing properties and healing efficiency. Furthermore, the materials, which undergo self-healing by chemical and physical mechanisms, exhibit rapid and efficient self-healing properties under semi-dry conditions. To prepare a supramolecular actuator using host–guest complexes, two approaches have been introduced. The first is the functionalization of a supramolecular gel actuator by changing the cross-linking density, and the second is the functionalization of a topological gel actuator by changing distances between the cross-linking points. Both actuators exhibit contractive bending behavior. This review summarizes advancements within the past ten years in supramolecular materials that function via the chemical mechanism of host–guest interactions and the physical mechanism of the sliding motion of ring molecules.     

Self-healing Polymeric Hydrogels: Toward Multifunctional Soft Smart Materials

The concept of self-healing that involves a built-in ability to heal in response to damage wherever and whenever it occurs in a material,analogous to the healing process in living organisms, has emerged a couple of decades ago. Driven primarily by the demands for life-like materials and soft smart materials, therefore, the development of self-healing polymeric hydrogels has continually attracted the attention of the scientific community. Here, this review is intended to give an in-depth overview...     

兼具导热和自修复功能的聚合物复合材料

针对聚合物复合材料存在的结构受损导致导热和力学强度降低的问题,提出利用导热填料增强自修复聚合物,实现导热性能和力学强度的快速修复.通过对双(3-氨丙基)封端的聚二甲基硅氧烷(H2N-PDMS-NH2)进行端基改性,得到脲基嘧啶酮(UPy)双封端的聚二甲基硅氧烷(UPy-PDMS-UPy),于60°C下20 h后拉伸强度修复效率可达86.6%.进一步填充羟基化氮化硼(mBN)制备兼具自修复功能的导热复合材料,研究发现mBN的填充导致复合材料强度提高但韧性降低,对导热性能和自修复功能分别起积极和不利影响.当mBN含量为30 wt%时,热导率高达2.579 W·m-1·K-1,于60°C下40 h后拉伸强度修复效率达82.0%.红外热像仪显示,损伤处接触10 h后,m BN-30/UPy-PDMS-UPy上表面温度接近初始温度,展现出导热通路的修复特征,实现导热与自修复功能的兼备.     

基于金属配位键的自修复、可重塑聚丁二烯橡胶的合成及性能

橡胶材料通常因经过硫化及补强等工艺处理而呈现出热固性,因而难以被回收处理,容易造成严重的资源浪费和环境污染.本文通过在聚丁二烯上修饰羧酸基团,再加入锌离子(Zn2+)与羧酸配位,制备了基于金属配位键交联的自修复橡胶(PB-COOH/Zn2+).该橡胶具有良好的机械性能和优秀的自修复及重塑性能,在70℃下修复3 h,其韧性可以恢复到初始强度,修复效率可达100%. PB-COOH/Zn2+较高的聚合物链段运动能力及配位键交联网络良好的动态性不仅赋予其优异的修复性能,还使得其在较温和的条件下可以进行多次重塑,在70℃及5 MPa的条件下重塑3次仍能保持原有的机械性能.此外,通过在PB-COOH/Zn2+中掺杂适量的碳纳米管,不仅增强了其机械性能,还使其具备了电致修复及传感能力,扩宽了PB-COOH/Zn2+作为环境友好型材料的应用前景.     

基于多重可逆作用的自修复聚氨酯弹性体的制备及性能

在聚氨酯主链上引入可逆二硫键, 同时使用硼酸构建的硼酸酯键作为可逆交联点, 使聚氨酯内部形成交联网络结构, 制备了一种兼具高强度、 高韧性及高修复效率的自修复聚氨酯弹性体. 红外光谱、 动态力学分析、 力学测试、 电子显微镜及修复测试结果表明, 制备的自修复聚氨酯具有硬而韧的特性, 原样强度高达23.3 MPa, 断裂伸长率可达1177%, 并且修复条件温和, 剪断拼接的试样经60 ℃, 24 h修复后可恢复99%的原样强度, 且该修复过程可重复多次进行. 此外, 该材料还具有多通道修复特性, 通过热修复或水辅助热修复的方式均可实现材料的修复, 并且水辅助热修复速率更快.     

Micromechanical assessment of PMMA microcapsules containing epoxy and mercaptan as self-healing agents

Mechanical properties of microcapsule shell have great influence on microcapsule suitability as a mechanical trigger in a self-healing composite. The elastic modulus and hardness of polymethyl methacrylate (PMMA) microcapsules containing epoxy prepolymer (EC 157) and pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) as healing agents were investigated using nanoindentation technique. The influence of the PMMA average molecular weight (M_W), the kind of core material, and the mechanical mixing rate on the mechanical properties of the microcapsule shell were studied using the Taguchi experimental design approach. The results indicated that the most important factors which affect the elastic modulus and the hardness of microcapsules shell are the Mw of PMMA and the kind of core material. The average elastic modulus of PMMA shell of epoxy and mercaptan-loaded microcapsules was found between 2.386 and 3.495 GPa. The hardness of PMMA shell of healing agent microcapsules was obtained in the range of 0.064–0.219 GPa. This constitutes essential knowledge in order to design capsules with tailored properties for self-healing materials.     

Self-Healing Polymer Composites: Prospects,Challenges, and Applications

Self-healing polymer composites possess the inherent ability to heal the damage event autonomically or non-autonomically with external intervention. These advanced materials can be commercialized if the challenges and limitations of different self-healing mechanisms are well known and considered. These include capsule-based healing systems, vascular healing systems, and intrinsic healing systems. To date, most of the reviews have studied and reported on different self-healing mechanisms including their response to impact, fatigue, and corrosion tests. This review focuses mostly on extrinsic and intrinsic self-healing polymer composites which have been reported during the past five years by comparing their healing efficiency, advantages, and challenges in the prospect of their future development as well as their possible applications across various industries such as aerospace, automobile, coating, electronics, energy, etc.     

自愈合聚合物材料的研究进展Ⅰ.传统修复方法及热固性自愈合材料的制备和表征

自愈合聚合物材料是受自我修复生物体系的触发而发展的,这是一个新兴迷人的研究领域,可以明显拓宽聚合物材料的工作寿命和广泛应用的安全性.参考近年来的文献资料,文章着重介绍了传统的修复聚合物材料的方法,以及各种热固性自愈合材料的制备和表征,其中最主要的制备方法是中空纤维法和微胶囊法.     

自修复聚合物材料的研究进展

针对聚合物材料在使用过程中难以检测的损伤,人们引入了自修复概念。本文就近年来自修复聚合物材料的研究进展作了系统综述。根据自修复过程是否使用修复剂,聚合物材料(包括聚合物基复合材料)的自修复可分为外援型和本征型两大类。外援型自修复借助于外加修复剂实现自修复,主要包括埋植微胶囊化修复剂和埋植中空纤维化修复剂两种方法。微裂纹的破坏使微胶囊或中空纤维释放修复剂,修复剂发生化学反应,键合裂纹面,达到自修复的效果。这种方法相对比较简单,修复效果较好,但不能重复进行,而且可选用的修复剂种类有限。本征型自修复则借助于体系内存在的Diels-Alder反应、动态共价化学、双硫键反应、含有氢键的超分子结构、π-π堆叠及离子聚合物等来完成,这些特殊的分子结构所涉及的化学反应是可逆的。本征型自修复聚合物材料的制备过程较为复杂,但这种自修复可以反复多次有效,从而延长了聚合物材料的使用寿命。本文针对以上两大类自修复聚合物材料体系的特点和应用进行综述,并展望其发展方向。     

Self-healing mineralized hydrogel scaffolds for stretch-triggered dye release

Hydrogels, with self-healing properties that can self-repair spontaneously when subjected to mechanical stress, are gaining popularity in the biomedical field. Numerous attempts have been made to create distinctive hydrogels with self-healing properties, along with stimuli-responsiveness and biocompatibility. Several techniques exist for fabricating hydrogels, including physical and chemical crosslinking via the creation of covalent bonds, and so on. Here, we prepared self-healing, stimuli-responsive, mineralized hydrogel by simply dissolving Kollidon 90-F, sodium chloride (NaCl), and potassium carbonate (K₂CO₃) in an aqueous solution. The dissociated CO₃²⁻ replaces the water molecules from the Kollidon 90-F polymer backbone and facilitates the cross-linking of the polymer chain, resulting in hydrogel formation. In addition, the in-situ produced sodium carbonate (Na₂CO₃) strengthens the hydrogel network. We optimized the mineralized hydrogels by taking various metal salts and different concentrations of K₂CO₃. The optimized hydrogel showed good stability over a period of time, was able to maintain viscoelastic properties, possessed good self-healing ability, and showed a shape retention ability. The shear-thinning property demonstrated by the optimized hydrogel could open a ray of hope in the bioprinting or 3D printing industry. Further, the stretch-responsive release of dye from the Self-healing mineralized hydrogel (SHMH) matrix confirms the mechanoresponsive behavior of the hydrogel. Overall, the findings could be utilized in the future to fabricate a stable drug delivery system that can autonomously release the drug molecules when stretched by daily processes such as joint movements.     

强韧型自愈合水凝胶的研究进展

水凝胶作为一种由大量水和与众不同的三维网状结构构成的智能软材料,已经广泛应用于许多领域,如药物输送、软骨修复、废物处理及电子设备等。然而,水凝胶不良的机械性能及自愈合性极大地限制了它们的潜在应用。目前已报道的韧性水凝胶通常不具有或只有很弱的自修复性,而自修复水凝胶通常机械性能非常弱。因此,研发具有高效自修复性能和优异机械性能的水凝胶材料,无论是从学术角度还是工业角度都是非常重要的。本文总结了近些年来强韧型自愈合水凝胶的最新研究进展,从其制备方法、性能等方面进行了简要介绍,并对未来的发展前景进行了展望。     

Design and synthesis of self-healing polymers

Self-healing polymers represent a class of materials with built-in capability of rehabilitating damages. The topic has attracted increasingly more attention in the past few years. The on-going research activities clearly indicate that self-healing polymeric materials turn out to be a typical multi-disciplinary area concerning polymer chemistry, organic synthesis, polymer physics, theoretical and experimental mechanics, processing, composites manufacturing, interfacial engineering, etc. The present article briefly reviews the achievements of the groups worldwide, and particularly the work carried out in our own laboratory towards strength recovery for structural applications. To ensure sufficient coverage, thermoplastics and thermosetting polymers, extrinsic and intrinsic self-healing, autonomic and non-autonomic healing approaches are included. Innovative routes that correlate materials chemistry to full capacity restoration are discussed for further development from bioinspired toward biomimetic repair.     

自愈合聚合物材料的研究进展Ⅱ.热塑性聚合物的自愈合机理

自愈合聚合物材料是受自我修复生物体系的触发而发展的,这是一个新兴迷人的研究领域,可以明显拓宽聚合物材料的工作寿命和广泛应用的安全性.文章是《自愈合聚合物材料的研究进展Ⅰ.传统修复方法及热固性自愈合材料的制备和表征》的续篇,进一步介绍可自我修复的热塑性高分子材料的愈合机理.     

单体结构对基于离子作用的自修复光固化材料性能的影响

本文研究了单体结构及其比例对基于离子作用的自修复光固化材料光聚合行为、力学性能,以及自修复性能的影响。结果表明：改变软硬单体种类及其比例不会改变自修复光固化体系的光聚合行为。增加软单体含量和降低硬单体含量,材料的拉伸应变和修复效率随之增加,断裂应力随之降低。硬单体中刚性环会增加聚合物链间的内摩擦力,使材料断裂应力增加,软单体中柔性醚链则降低链间范德华力,增强链移动性,提高材料的拉伸应变和修复效率。软单体为丙烯酸正丁酯（BA）及硬单体为丙烯酸异冰片酯（IBOA）的样品IB7-BA3展现出较好的综合性能,断裂应力为1.42 MPa,拉伸应变为295%,修复效率高于90%。