超分子聚合物的自愈合行为

由于非共价键的选择性、可逆性和动态性,超分子聚合物非常适合作为自愈合材料应用,体现了感知和响应功能的智能特征。超分子聚合物的自愈合机理是通过非共价键相互作用实现的,即超分子结构的形成与解离。综述氢键型、?-?堆叠型、金属配位型、拓扑聚合物等类型的超分子聚合物的自愈合行为。     

Self-Healing Dynamic Polymeric Systems

The concept of self-healing has created a paradigm shift in the development of a new kind of responsive polymeric materials, which have traditionally been used in a passive role. Inspired by nature, the advancements made in this nascent field of research have given materials the ability of not only sensing damage but also responding and mending themselves in an appropriate manner. Self-healing in polymers can be autonomous, without the need for human intervention, or nonautonomous, requiring some form of external stimulus. The latter type involves the incorporation of dynamic bonds within the polymeric system, giving the ability to heal multiple times. This minireview discusses some of the prominent self-healing polymeric systems that harness different dynamic bond chemistries, with the aim of highlighting the potential of dynamic bonds to prepare such advanced materials.     

基于动态硼酸酯键聚合物的构筑和应用研究进展

基于动态硼酸酯键构筑的聚合物有一定的自修复能力和对刺激的多重响应性, 能够通过诱导材料内部物理/化学结构的拓扑重组并以此来响应生物信号的变化。本文综述了基于水解/再酯化、二醇硼酸酯之间的酯交换和硼酸酯之间的酯交换3种不同的硼酸酯酯交换机制构筑的多种天然/非天然高分子材料; 通过传统共价键和硼酸酯动态共价键协同作用设计更加稳定的四面体硼酸盐结构来解决硼酸酯基聚合物稳定性较差的策略; 硼酸酯基聚合物在生物医药、传感器和可回收材料等多领域的应用潜力。重点介绍了硼酸酯键与其它动态键协同作用制备理想的聚合物材料, 如水凝胶、有机凝胶、液晶材料和可回收纳米材料等。     

Room-temperature self-healing and reprocessing of Diselenide-containing waterborne polyurethanes under visible light

Realizing environmentally friendly polymers that could heal themselves at room temperature is an important challenge for sustainable societies. Herein, environment-friendly self-healing waterborne polyurethanes (WPUs) containing diselenide groups were synthesized. The healing efficiency could reach up to more than 90% after exposed to visible light for 48 hours and the fractured location was allowed to be healed repeatedly. Meanwhile, a fast room-temperature self-healing could also be achieved in 4 hours with a healing efficiency of ~84%. The healing process was a combination of rapid closure of crack surfaces at the beginning due to the rebuilding of hydrogen bonds and gradual restoration of mechanical property derived from diselenide metathesis across the fractured interface. At the same time, room-temperature reprocessing could be also achieved with the aid of external pressure under visible light. Moreover, the prepared diselenide-containing WPUs exhibited excellent emulsion stability. The present work would be hopefully developed into a methodology of design and fabrication of environmentally friendly photo-sensitive polymers with self-healing and reprocessing abilities. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47071.     

A review on the self-healing ability of epoxy polymers

This review encompasses the research progress on self-healing properties of epoxy polymers and is divided into two categories: material supplement and energy supplement. The central concept of material supplement revolves around the addition of functional composite materials, such as, hollow fiber and microcapsule, to repair the micro-cracks of epoxy polymers. In contrast, the energy supplement is based on the concurrent incorporation of some functional groups into the thermosetting epoxy polymers. These functional chemical groups participate in the construction of a three-dimensional network structure of thermosetting materials and successfully enter the block copolymer of epoxy polymers. When the micro-cracks are developed in the resin upon exterior impact, these functional groups automatically absorb energy from the outside to perform chemical reactions and automatically repair their micro-cracks following the self-healing phenomenon. Five kinds of reversible reactions are introduced for energy supply and are discussed in detail. Finally, a summary and comparison of the self-healing methods covered in this review and the application prospect of self-healing epoxy polymers are summarized.     

Supramolecular Polymers – we've Come Full Circle

Since the first polymers were discovered, scientists have debated their structures. Before Hermann Staudinger published the brilliant concept of macromolecules, polymer properties were generally believed to be based on the colloidal aggregation of small particles or molecules. From 1920 onwards, polymers and macromolecules are synonymous with each other; i. e. materials made by many covalent bonds connecting monomers in 2 or 3 dimensions. Although supramolecular interactions between macromolecular chains are evidently important, e. g. in nylons, it was unheard of to proposing polymeric materials based on the interaction of small molecules. Breakthroughs in supramolecular chemistry, however, showed that polymer materials can be made by small molecules using strong directional secondary interactions; the field of supramolecular polymers emerged. In a way, we have come full circle. In this essay we give a personal story about the birth of supramolecular polymers, with special emphasis on their structures, way of formation, and the dynamic nature of their bonding. The adaptivity of supramolecular polymers has become a major asset for novel applications, e. g. in the direction for the sustainable use of polymers, but also in biomedicine and electronics as well as self-healing materials. The lessons learned in the past years include aspects that forecast a bright future for the use of supramolecular interactions in polymer materials in general and for supramolecular polymers in particular. In order to give full tribute to Staudinger in the year celebrating 100 years of macromolecules, we will show that many of the concepts of macromolecular polymers apply to supramolecular polymers, with only one important difference with fascinating consequences: the dynamic nature of the bonds that form polymer chains.     

Development of a Strong,Recyclable Poly(dimethylsiloxane) Elastomer with Autonomic Self-Healing Capabilities and Fluorescence Response Properties at Room Temperature

With the recent emphasis on environmental protection measures, there are increasingly strong demands for environment-friendly multifunctional materials, so research regarding high-performance, recyclable, functional materials with self-healing abilities is of great interest. However, the comprehensive mechanical properties of most available self-healing materials are insufficient; to date, most developed materials are either tough but brittle or flexible but weak. This report describes the application of a crosslinking strategy based on multiple dynamic bonds for the development of an autonomically self-healing, multifunctional, boroxine-containing poly(dimethylsiloxane) elastomer (PDMS-BN). This approach takes advantage of well-designed intermolecular and intramolecular nitrogen-coordinated boroxines by using a synergetic dynamic mechanism. The elastomers exhibit enhanced comprehensive mechanical properties (with maximum strength up to 1.72 MPa, elongation at break up to 307%, Young's modulus up to 11.18 ± 0.52 MPa, and toughness up to 4.92 MJ m⁻³) and highly autonomic self-healing capabilities, with ≈96% efficiency at room temperature for 48 h. Moreover, the PDMS-BN elastomer can be recycled multiple times via crushing/molding or disassembling/casting processes, without losing their original mechanical robustness. The as-prepared elastomers also demonstrate good adhesive properties and a unique fluorescence-quenching response in the presence of Fe³⁺ ions.     

Antibacterial self-healing anticorrosion coatings from single capsule system

It is highly desirable to develop self-healing anticorrosion coatings with enhanced antibacterial function to prevent the scratched area to be fouled or corroded in harsh environments. Herein, we report antibacterial self-healing anticorrosion coatings via the simple incorporation of the easily synthesized single polymer microcapsule system. Well-defined polymer microcapsules containing isophorone diisocyanate (IPDI) as a healing agent and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as antibacterial molecules were synthesized by one-pot polymerization. The diameter and core fraction were around 30 μm and 90%, respectively. The active DCOIT content in the core material could be precisely controlled by adjusting the DCOIT/IPDI feeding ratio. The DCOIT/IPDI microcapsules-embedded protective coating exhibits an adaptive self-healing anticorrosion property, as shown by electrochemical test under the condition of the salt-water immersion. Furthermore, the self-healing coating showed efficient antibacterial function against Escherichia coli and Pseudomonas aeruginosa, which is due to the released active biocide molecules on the damaged surfaces. In contrast to other systems, this single capsule system without any catalyst is perspective for extending the service time of the antibacterial self-healing materials in harsh environment.     

An innovative synergy between solution electrospinning process technique and self-healing of materials. A critical review

An overview of recent advances related to self-healing (SH) of materials and solution electrospinning (SEP) is provided. SH agents (SHAs) in electrospun form seems to be one of the most promising approaches for SH and exhibit an increasing trend for a wide range of applications. The aim of the current review paper is to report contributions and advances related to SH of materials by using SHAs in electrospun form and provide insights for further improvement of this promising technology. More specifically, this paper contains investigations in which the SHAs or the SHA containers were exclusively prepared by SEP.     

Self-healing bio-based furan polymers cross-linked with various bis-maleimides

A series of bio-based self-healing polymers was prepared by cross-linking a furan polymer, poly(2,5-furandimethylene succinate), with bis-maleimide compounds by means of Diels–Alder reactions. In addition to the amount of the bis-maleimide linker, the molecular structure of the bis-maleimide played a key role in determining the extent of the Diels–Alder reaction and the mechanical and healing properties of the polymers. Bis-maleimides with phenylene rings markedly enhanced the tensile strength of the network polymers but hindered healing. In contrast, bis-maleimides with a flexible molecular structure tended to improve the polymer elongation, affording polymers with excellent healing ability. The efficiencies of self-healing (=healing without any external stimulus) and healing with an assistance of solvent (CHCl₃) were over 70% and 80%, respectively, for the network polymer crosslinked by bis-maleimide with flexible long-alkyl segment. Thus, our results indicate that the choice of bis-maleimide linker is an important factor for designing furan-maleimide–based self-healing polymers.     

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.     

Study on self-healing behavior of the layer-by-layer assembled polyethylenimine/poly(acrylic acid) film

Many studies have demonstrated that intrinsic self-healing polyelectrolyte coatings can be fabricated by exponentially growing Layer-by-Layer (LbL) assembled polyelectrolyte multilayers. However, due to the lack of controlled self-healing evaluation methods, the researches on self-healing properties have remained at some simple qualitative characterization. In our study, a self-healing branched polyethylenimine (bPEI)/poly(acrylic acid) (PAA) films is successfully prepared by LbL and a new systematical self-healing evaluation method is developed. The cuts with controllable depth, width, and period can be easily fabricated on bPEI/PAA films through the colloidal lithography and photolithography. Colloidal lithography, as a facile, low-cost, and versatile unconventional technique, can realize precise and repetitive fabrication of cuts at the same sample and in the same area, which will be beneficial to the systematic study and evaluate self-healing behavior. The self-healing behaviors on the different cuts are observed by scanning electron microscope (SEM). The SEM results reveal that bPEI/PAA film could realize damage/healing process for multiple times at the same sample and in the same area. In addition, the self-healing abilities of the LbL films are related to the damage number, depth, and width of cuts. With the increase of damage number, depth, and width of cuts, the loss of polyelectrolyte was also increased, which lead to the flow of remaining polyelectrolytes were not enough to heal the cuts. This work provides a new route to systematically characterize the self-healing ability of bPEI/PAA films as well as other polyelectrolyte films.     

Rheological and mechanical properties of dynamic covalent polymers based on imine bond

Dynamic covalent polymers based on imine bond (FPIs), which are capable of reorganizing their constitution on the molecular level, are prepared from bio-based dimer fatty acids. The irregular structure of carbon chains in dimer fatty acids leads to the amorphous nature of FPIs. The effect of imine bond on the glass transition temperature of FPIs is studied by differential scanning calorimetry. The linear viscoelasticity of FPIs is investigated by small amplitude oscillatory shear tests and analyzed by using the Likhtman-McLeish theory. It is found that the rheological behavior of FPIs is similar with that of static, linear entangled polymers predicted by Likhtman-McLeish theory, when the dynamic chain arrangements caused by imine-bond exchange is not active enough. For FPIs, the temperature variation of viscosity is still following the Arrhenius law with an activation energy of ~50 kJ mol⁻¹. Owing to the thermal adaptability, FPIs demonstrate great malleability, self-healing capability and processing stability at elevated temperatures.     

Electrospun Nanofibers: Materials,Synthesis Parameters,and Their Role in Sensing Applications

Since the last decade, electrospinning is garnering more attention in the scientific research community, industries, applications like sensing (glucose, H₂O₂, dopamine, ascorbic acid, uric acid, neurotransmitter, etc.), biomedical applications (wound dressing, wound healing, skin, nerve, bone tissue engineering, and drug delivery systems), water treatment, energy harvesting, and storage applications. This review paper provides a brief overview of the electrospinning method, history of the electrospinning, factors affecting the electrospun nanofibers, and their morphology with different materials and composites (metals, metal oxides, 2D material, polymers and copolymers, carbon-based materials, etc.) used in the electrospinning technique with optical spinning parameters. Moreover, this paper deliberates the application of electrospun nanofibers and fibrous mats for sensing (electrochemical, optical, fluorescence, colorimetric, mechanical, photoelectric, mass sensitive change, resistive, ultrasensitive, etc.) in most illustrative representations. In the end, the challenges, opportunities of the electrospun nanofibers, and new direction for future progress are also discussed.     

Self-healable and thiol–ene UV-curable waterborne polyurethane for anticorrosion coating

Thiol–ene ultraviolet-curable waterborne polyurethane (WPU) crosslinked networks capable of self-healing of cracks were developed for anticorrosion coating application. The healing mechanism is attributed to the rearrangement of the crosslinked networks caused by triethylamine-catalyzed thiol–disulfide exchange reaction proved by high-performance liquid chromatography, gel permeation chromatography, and rheology tests. The crack remendability can be repeated for at least two times as demonstrated by visual inspection. Moreover, the self-healing effect was further demonstrated in terms of corrosion and electrochemical tests. Comparatively, the control specimens without disulfide bonds were not self-healable. The present study provides a simple way for achieving self-healing WPU to conform to the trend of development of high performance and environmental friendly anticorrosive coatings. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47700.     

Soluble semi-conductive chelate polymers containing Cr(III) in the backbone: Synthesis, characterization, optical, electrochemical, and electrical properties

Soluble kinds of coordination polymers containing Cr(III) ion in the backbone were synthesized. Structures of the polymers were characterized by FT-IR, UV-vis, ¹H and ¹³C NMR, and size exclusion chromatography (SEC). Thermal degradation data were obtained by TG-DTA and DSC techniques. Cyclic voltammetry (CV) measurements were carried out and the HOMO-LUMO energy levels and electrochemical band gaps were calculated. Additionally, the optical band gaps (E_g) were determined by using UV-vis spectra of the materials. Electrical conductivity measurements of doped (with iodine) and undoped polymers related to temperature were carried out by four-point probe technique using a Keithley 2400 electrometer. Measurements were made by using the polymeric films deposited on ITO glass plate by dip-coating method. Also, absorption spectra of doped polymeric films were recorded by a single beam spectrophotometer showing that doping procedure causes shifting in absorption spectra. Their abilities of processing in gas sensors were also discussed. According to obtained results the synthesized chelate polymers are semi-conductors having polyconjugated structures. Also, P-2 is the most electro-conductive polymer among the synthesized, while P-1 is the most thermally stable one.     

Polymerizations with elemental sulfur: A novel route to high sulfur content polymers for sustainability,energy and defense

Recent developments in the polymerizations of elemental sulfur (S₈) to prepare high sulfur content polymers are reviewed. While the homopolymerization of S₈ via ring-opening processes to prepare high molar mass polymeric sulfur has long been known, this form of polymeric sulfur is chemically unstable and depolymerizes back to S₈. In the current report, we discuss the background into the production of sulfur via petroleum refining and the challenges associated with utilizing S₈ as a chemical reagent for materials synthesis. To circumvent these long standing challenges in working with sulfur, the use of S₈ as a reaction medium and comonomer in a process termed, inverse vulcanization, was developed to prepare chemically stable and processable sulfur copolymers. Furthermore, access to polymeric materials with a very high content of sulfur–sulfur (SS) bonds enabled for the first time the creation of materials with useful (electro)chemical and optical properties which are reviewed for use in Li–S batteries, IR imaging technology and self-healing materials.     

Advances in healing-on-demand polymers and polymer composites

Healing-on-demand materials exhibit the capability to close cracks and heal the closed/narrowed cracks when needed and to recover functionality using intrinsic or extrinsic resources. In this paper, advances in healing-on-demand polymers and polymer composites in the past decade are reviewed, covering different schemes and technologies used to trigger crack closure and to heal molecularly. A balanced review on non-load-bearing polymers and polymer composites as well as load-carrying polymers and polymer composites is presented. The progress in self-healing polymers and polymer composites has been well discussed recently in the literatures. In this review, therefore, less attention has been paid on what has been widely reported; we primarily focus on healing-on-demand materials concerned with large volume damage healing by a close-then-heal (CTH) strategy. The healing-on-demand material by the CTH approach undergoes a process of crack closure, followed by crack healing with healing agents. Healing theories, including those within the continuum damage mechanics framework, and healing efficiency evaluations are also reviewed. Perspectives on future development in this emerging research area are discussed.     

Platinum-terpyridine complexes in polymers: A novel approach for the synthesis of self-healing metallopolymers

The synthesis of novel platinum-based metallopolymers for self-healing applications is presented. For this purpose, terpyridine-platinum complexes were studied using isothermal titration calorimetry regarding their complexation behavior with pyridine. The obtained knowledge was utilized for the preparation of metallopolymers using the reversible addition fragmentation chain-transfer -polymerization technique resulting in well-defined polymers. Crosslinking with a tetravalent pyridine-crosslinker enabled the synthesis of a metallopolymer network featuring self-healing properties. From these experiments, more information about the molecular preconditions for the design of healable metal-containing polymers could be drawn enabling a further optimization of these systems in the future. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47064.     

超疏水表面自修复及应用的研究进展

超疏水表面因具有诸多优异特性而展现出良好的应用前景,但在实际应用中容易受到外界机械力损坏或化学侵蚀,赋予超疏水表面自修复性能可以较好地改善表面耐久性,延长其使用寿命。本文针对修复构成超疏水表面的微观结构与低表面能物质展开论述,介绍了在湿度、温度、光等外界因素的引发下超疏水表面对低表面能物质的修复行为与特点,以及以形状记忆聚合物为主制备的超疏水表面对微观结构进行修复的过程。此外,介绍了具有自修复性能的超疏水表面在防腐蚀、油水分离、防覆冰等领域的应用。最后,讨论了通过优化表面结构和化学组成开发自修复超疏水表面的挑战和前景,环保型且无需外界刺激即可迅速对微观结构与低表面能物质进行双重修复的超疏水表面具有重要的研究意义。