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。     

The Potential of Microencapsulated Self-healing Materials for Microcracks Recovery in Self-healing Composite Systems: A Review

The autonomic self-healing materials based on microcapsules have made major advancements for the repairing of microcracks in polymers and polymer composite systems. Self-healing encapsulated materials have the inborn ability to heal polymeric composites after being damaged by chemical and mechanical progressions. These intelligent micro-encapsulated self-healing materials possess great capabilities for recovering the mechanical as well aesthetic properties and barrier properties of the polymeric structures. Based on real world observations and experimental data, it is believed that microcracks and microcracking in polymeric materials can result because of many chemical and physical routes and is one of the foremost critical issues for polymeric materials. Especially in polymeric coatings, these microcracks can lead towards disastrous failure, and conventional healing systems like patching and welding cannot be used to repair microcracks at such a micro-level. Self-healing materials, especially, capsule based self-healing materials is a new field sought as an alternative to the conventional repairing techniques, requiring no manual intrusion and uncovering. This review covers the basic and major aspects of the microencapsulated self-healing approach like the effect of synthesis parameters on the size of microcapsules, healing efficiency determination, and the potential of the existing developed microencapsulated agents.     

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.     

氢键型碳纳米管增强自修复复合材料的制备和表征

使用低聚酸、二乙烯三胺以及尿素为原料,碳纳米管为增强剂,制备出兼具良好力学性能和室温(30 ℃)自修复性能的氢键型自修复复合材料,同时对材料通过氢键进行自修复的机制进行了合理推测。 首先,对不同碳纳米管添加量的自修复材料进行应力-应变性能测试。 结果发现,随着碳纳米管的添加,材料的应力、应变均有所提高,添加质量分数9%碳纳米管时,材料的应力达到4.1 MPa、应变达到6%以上。 对添加质量分数9%碳纳米管的自修复材料进行表面形态、自修复性能以及热稳定性能测试。 结果表明,碳纳米管与材料有良好的相容性,材料的表面与切面形态相似;在室温下自修复24 h,自修复效率达到100%;10次断裂-修复循环中自修复效率仍能保持90%以上;材料具有良好的热稳定性,最大失重速率下的温度为474.3 ℃。 为下一代类皮肤传感器以及可穿戴智能设备提供了一种选择,为未来该类型自修复聚合物复合材料在高拉伸强度领域的应用奠定了技术基础。     

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.     

A Shear-Thinning,Self-Healing,Dual-Cross Linked Hydrogel Based on Gelatin/Vanillin/Fe3+/AGP-AgNPs: Synthesis,Antibacterial, and Wound-Healing Assessment

A shear-thinning and self-healing hydrogel based on a gelatin biopolymer is synthesized using vanillin and Fe³⁺ as dual crosslinking agents. Rheological studies indicate the formation of a strong gel found to be injectable and exhibit rapid self-healing (within 10 min). The hydrogels also exhibited a high degree of swelling, suggesting potential as wound dressings since the absorption of large amounts of wound exudate, and optimum moisture levels, lead to accelerated wound healing. Andrographolide, an anti-inflammatory natural product is used to fabricate silver nanoparticles, which are characterized and composited with the fabricated hydrogels to imbue them with anti-microbial activity. The nanoparticle/hydrogel composites exhibit activity against Escherichia coli, Staphylococcus aureus, and Burkholderia pseudomallei, the pathogen that causes melioidosis, a serious but neglected disease affecting southeast Asia and northern Australia. Finally, the nanoparticle/hydrogel composites are shown to enhance wound closure in animal models compared to the hydrogel alone, confirming that these hydrogel composites hold great potential in the biomedical field.     

Adaptive Ion-Gel: Stimuli-Responsive,and Self-Healing Ion Gels

Ion gels are an emerging class of polymer gels in which a three-dimensional polymer network swells with an ionic liquid. Ion gels have drawn considerable attention in various fields such as energy and biotechnology owing to their excellent properties including nonvolatility, nonflammability, high ionic conductivity, and high thermal and electrochemical stability. Since the first report on ion gels (published ∼30 years ago), diverse functional ion gels exhibiting impressive physicochemical properties have been reported. In this review, recent developments in functional ion gels that can modulate their physical properties in response to environmental conditions are outlined. Stimuli-responsive ion gels that can adaptively undergo phase transitions in response to thermal and light stimuli are initially discussed, followed by an evaluation of diverse self-healing ion gels that can spontaneously mend mechanical damage through judiciously designed ion-gel networks.     

Thermally driven self-healing PEDOT conductive films relying on reversible and multiple Diels–Alder interaction

Thermally healing capability of cracks and defects is important and urgent for the safe operation and life extending of electric materials and devices. Here, by the combination of thermally driven reversible Diels–Alder (DA) interaction and in-situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT), a series of intrinsically conductive poly(3,4-ethylenedioxythiophene) (PEDOT)/DA composites possess intrinsically self-healing property under low-temperature (reverse DA reaction at 100°C; DA crosslinking at 60°C) stimulus were achieved. The crosslinking DA bonding reactions are multiple from the co-existence of pre-synthesized macromolecular polyurethane attached DA units (PU-DA) and 2,4-hexadiyne-1,6-diol (DADOL) in the films. PU-DA involved in the polymerization process of EDOT to endow PEDOT with outstanding solution-processability, uniform film making, and structural self-healing capability, while DADOL was added to enhance the cross bonding between polymer chains. This work will accelerate the research and application development of intrinsically self-healing conducting polymers for commercial capacitors, antistatic coatings, implantable, printable electronics, and so on.     

自愈合凝胶:结构、性能及展望

作为一种高分子智能材料,自愈合凝胶在解决软材料损伤修复以及凝胶-生物体组织之间的界面接口问题,实现软材料智能化、高效化和环境友好化具有重要意义.近年来利用动态建构化学的基本原理,通过动态非共价键、可逆动态共价键相互作用,设计了一系列具有良好自愈合性能的新型凝胶材料.本文以物理型和化学型动态自愈合凝胶为例,综述了自愈合凝胶的分子设计思路、性能,并分析了影响自愈合性能因素,并对其未来的发展进行了展望.     

Polymeric Halogen‐Bond‐Based Donor Systems Showing Self‐Healing Behavior in Thin Films

The synthesis and comprehensive characterization of a systematic series of cleft‐type anion receptors imbedded into a polymeric architecture is presented. For the first time, isothermal calorimetric titrations on polymeric halogen‐bond‐based donors were exploited to evaluate the dependence of the anion affinity on different key parameters (i.e. monomeric versus polymeric receptor, halogen versus hydrogen bonding, charge assistance). The combination of these donor systems with a copolymer bearing accepting carboxylate groups led to supramolecular cross‐linked polymer networks showing excellent intrinsic self‐healing behavior. FT‐Raman spectroscopy and nano‐indentation measurements were utilized to clarify the thermally induced self‐healing mechanism based on the formation of halogen bonds. These first self‐healing materials based on halogen bonds pave the way for new applications of halogen‐bond donors in polymer and material science.     

Enhanced self-healing driving force in polymer materials by regulating molecular structure

For self-healing polymers, obtaining excellent healing ability and mechanical properties usually need complex chemical structure, external healing conditions, and high manufacturing difficulty. Therefore, self-healing efficiency and rate, mechanical strength, and simple structure design as well as no additional healing conditions of the material are contradictory properties and are difficult to optimize simultaneously. Herein, self-healable thermoplastic poly (urethane urea) elastomers driven by surface energy were fabricated by the introduction of asymmetric alicyclic structures and the healing properties in polymers were optimized by regulating surface energy. The results showed that with the increasing of isophorone diamine contents, the surface energy driving force increased from 36 kPa to 149 kPa, the healing time decreased from 30d to 5d, and healing efficiency, and tensile strength reached 100.9% and 4.04 MPa at room temperature. At the same time, polymers also obtained a high healing efficiency under high-temperature healing conditions. The healing mechanism is that asymmetric alicyclic structures with steric hindrance and ring flip promote the dissociation of hydrogen bonds, provide sufficient chain mobility, decrease the junction density, and improve the surface energy as well as the dissociation and reconstruction of hydrogen bonds. Energetic polymer composites using thermoplastic poly (urethane urea) elastomers as matrix obtained excellent healing properties. This study will offer a novel healing approach for developing advanced self-healing polymer materials.     

Influence of Material Properties on the Damage-Reporting and Self-Healing Performance of a Mechanically Active Dynamic Network Polymer in Coating Applications

We conducted a detailed investigation of the influence of the material properties of dynamic polymer network coatings on their self-healing and damage-reporting performance. A series of reversible polyacrylate urethane networks containing the damage-reporting diarylbibenzofuranone unit were synthesized, and their material properties (e.g., indentation modulus, hardness modulus, and glass-transition temperature) were measured conducting nanoindentation and differential scanning calorimetry experiments. The damage-reporting and self-healing performances of the dynamic polymer network coatings exhibited opposite tendencies with respect to the material properties of the polymer network coatings. Soft polymer network coatings with low glass-transition temperature (~10 °C) and indentation hardness (20 MPa) exhibited better self-healing performance (almost 100%) but two times worse damage-reporting properties than hard polymer network coatings with high glass-transition temperature (35~50 °C) and indentation hardness (150~200 MPa). These features of the dynamic polymer network coatings are unique; they are not observed in elastomers, films, and hydrogels, whereby the polymer networks are bound to the substrate surface. Evidence indicates that controlling the polymer’s physical properties is a key factor in designing high-performance self-healing and damage-reporting polymer coatings based on mechanophores.     

One-Pot,Open-Air Synthesis of Flexible and Degradable Multifunctional Polymer Composites with Adhesion,Water Resistance,Self-Healing,Facile Drug Loading,and Sustained Release Properties

Developing proper wound management via wound dressings represents a global challenge. Ideal wound dressings shall encompass multiple integrated functionalities for variable, complex scenarios; however, this is challenging due to the complex molecular design and synthesis process. Herein, polymer composites, cross-linked poly(styrene oxide-co-hexaphenylcyclotrisiloxane)/crosslinked poly(hexaphenylcyclotrisiloxane) (cP(SO-co-HPCTS)/cPHPCTS) with multiple functionalities are prepared by a one-step, open-air method using catalytic ring-opening polymerization. The introduction of a mobile polymer cP(SO-co-HPCTS) endows the composite with good flexibility and self-healing properties at human body temperature. The hydrophobic groups in the main chain provide hydrophobicity and good water resistance, while the hydroxyl groups contained in the end groups enable good adhesion properties. Drugs can be efficiently loaded by blending and then sustainably release from the polymer composite. The material can rapidly degrade in a tetrahydrofuran solution of tetrabutylammonium fluoride due to its Si O Si bonds. The facile, one-step, open-air synthesis procedure and multiple functional properties integrated into the composites provide good prospects for their extensive application and batch production as wound dressing materials.     

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%。     

Developing a Self‐Healing Supramolecular Nucleoside Hydrogel Based on Guanosine and Isoguanosine

Recently, supramolecular hydrogels have attracted increasing interest owing to their tunable stability and inherent biocompatibility. However, only few studies have been reported in the literature on self‐healing supramolecular nucleoside hydrogels, compared to self‐healing polymer hydrogels. In this work, we successfully developed a self‐healing supramolecular nucleoside hydrogel obtained by simply mixing equimolar amounts of guanosine (G) and isoguanosine (isoG) in the presence of K⁺. The gelation properties have been studied systematically by comparing different alkali metal ions as well as mixtures with different ratios of G and isoG. To this end, rheological and phase diagram experiments demonstrated that the co‐gel not only possessed good self‐healing properties and short recovery time (only 20 seconds) but also could be formed at very low concentrations of K⁺. Furthermore, nuclear magnetic resonance (NMR), powder X‐ray diffraction (PXRD), and circular dichroism (CD) spectroscopy suggested that possible G₂isoG₂‐quartet structures occurred in this self‐healing supramolecular nucleoside hydrogel. This co‐gel, to some extent, addressed the problem of isoguanosine gels for the applications in vivo, which showed the potential to be a new type of drug delivery system for biomedical applications in the future.     

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.     

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℃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℃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,mBN-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.     

Maleimide Self-Reaction in Furan/Maleimide-Based Reversibly Crosslinked Polyketones: Processing Limitation or Potential Advantage?

Polymers crosslinked via furan/maleimide thermo-reversible chemistry have been extensively explored as reprocessable and self-healing thermosets and elastomers. For such applications, it is important that the thermo-reversible features are reproducible after many reprocessing and healing cycles. Therefore, side reactions are undesirable. However, we have noticed irreversible changes in the mechanical properties of such materials when exposing them to temperatures around 150 °C. In this work, we study whether these changes are due to the self-reaction of maleimide moieties that may take place at this rather low temperature. In order to do so, we prepared a furan-grafted polyketone crosslinked with the commonly used aromatic bismaleimide (1,1′-(methylenedi-4,1-phenylene)bismaleimide), and exposed it to isothermal treatments at 150 °C. The changes in the chemistry and thermo-mechanical properties were mainly studied by infrared spectroscopy, ¹H-NMR, and rheology. Our results indicate that maleimide self-reaction does take place in the studied polymer system. This finding comes along with limitations over the reprocessing and self-healing procedures for furan/maleimide-based reversibly crosslinked polymers that present their softening (decrosslinking) point at relatively high temperatures. On the other hand, the side reaction can also be used to tune the properties of such polymer products via in situ thermal treatments.