基于可逆共价键自修复聚氨酯的研究进展

聚氨酯作为一种新兴的有机高分子材料,被誉为"第五大塑料",以其优异的综合性能而广泛应用于轻工、建筑、汽车、航空和航天等领域.但是,其在加工或使用过程中,难免因外力作用而发生结构破坏,从而极大地降低了材料的力学性能和产品的使用寿命.可逆共价键是一种能够在一定条件下实现可逆断裂与重组的动态共价键.因此,将其引入聚氨酯分子链...     

Thermo‐reversible healing in a crosslinked polymer network containing covalent and thermo‐reversible bonds

The self‐healing behavior of a modified ureido‐amide based thermoplastic hybrid elastomer was investigated by increasing the concentration of non‐reversible (covalent) bonds compared to reversible (hydrogen) bonds. A crosslinked polymer network was synthesized using varying amounts of diglycidylether of bisphenol A and reacting with the ureido‐amide thermoplastic. Increasing epoxy content produced a more rigid and thermally stable hybrid network, which in turn decreased overall thermo‐reversible or healing behavior. Fracture toughness recoveries varied from 25% for the system containing the greatest number of covalent bonds to well over 200% for systems containing higher thermoplastic content. Substantial levels of healing, about 62% recovery, were still achieved despite the crosslinked network having a T_g above room temperature, 31°C as measured by differential scanning calorimetry (DSC). Dynamic mechanical thermal analysis was used to monitor thermo‐reversible behavior of the elastic moduli and thus probe molecular mobility within the glassy state. The extent and rate of recovery of the elastic modulus was dominated by the extent of thermal activation above the glass transition temperature. Fourier transform infrared spectroscopic and DSC studies confirmed that reacting the thermoplastic with an epoxy resin produced a covalently bonded crosslinked network and the epoxide groups were completely consumed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A biomimic shape memory polymer based self-healing particulate composite

In a previous study, a biomimic two-step self-healing scheme (close-then-heal (CTH)) by mimicking human skin has been proposed for self-healing structural-length scale damage [Li and Uppu. Composites Science and Technology 2010; 70: 1419-1427]. The purpose of this study is to validate this idea by fabricating a composite with thermoplastic particles (Copolyster) dispersed in a shape memory polymer matrix (Veriflex Polystyrene). In this particulate composite, the confined shape recovery of the shape memory matrix is utilized for sealing (closing) cracks and the thermoplastic particles are used for molecular-length scale healing. In this study, 6% by volume of thermoplastic particles was used. Beam specimens were prepared and programmed by compression in the longitudinal direction to 6.7% of pre-strain. Structural-length scale damage was then created by producing a notch in the programmed beam specimens per ASTM D 5045. The notched beam specimens were then tested to fracture. The fractured specimens were healed per the close-then-heal mechanism and tested again to fracture. This fracture-healing test lasted for 5 cycles. The healing efficiency was evaluated per the peak-bending load. SEM was used to examine healed cracks at micro-length scale while EDS was used to evaluate molecular-length scale healing. It is found that over 65% of the peak bending load can be repeatedly recovered and the structural-length scale damage (notch) is healed at molecular-length scale.     

基于动态共价键的pH响应自修复水凝胶的制备与评价

以α-甲基丙烯酸(MAA)和2-丙烯酰胺-2-甲基丙磺酸(AMPS)的共聚物P(MAA/AMPS)及聚乙烯醇(PVA)为单体、十水合四硼酸钠为交联剂合成了P(MAA/AMPS)-PVA二重互穿网络的pH响应水凝胶.通过SEM、FTIR、GPC、TGA-DTG和流变仪等表征了水凝胶的表面形貌和化学状态;测定了水凝胶的溶胀性﹑pH响应性﹑自修复性和流变性.结果表明,水凝胶形成了稳定的互穿网络结构且具有pH敏感性、自修复性;PVA羟基与硼酸根离子形成的共价配位硼酸酯键使水凝胶具备自修复性并受介质酸碱性的控制;力学性能测定结果显示,自修复水凝胶(SB用量为2.5％,水凝胶溶胀度为4)拉伸强度668 kPa,断裂伸长率可达665％,修复效率可达81％.     

基于动态共价键的pH响应自修复水凝胶制备与评价

以α-甲基丙烯酸、2-丙烯酰胺-2-甲基丙磺酸共聚产物和聚乙烯醇为单体，十水合四硼酸钠为交联剂合成P(MAA /AMPS)-PVA二重互穿网络的pH响应水凝胶；通过扫描电子显微镜(SEM)、红外光谱(FTIR)、凝胶渗透色谱（GPC）、热重分析(DSC-TG)和流变仪等表征了水凝胶的表面形貌和化学状态；测定了水凝胶的溶胀性﹑pH响应性﹑自修复性和流变性。结果表明，水凝胶形成稳定的IPN互穿网络结构且该水凝胶具pH敏感性、自修复性；PVA羟基与硼酸根离子形成的共价配位硼酸酯键决定水凝胶自修复性并受到介质酸碱控制；力学性能测定结果显示，自修复水凝胶拉伸强度668 kPa,断裂伸长率可达665%，修复效率可达81%。     

基于动态共价键的可自愈合聚合物凝胶

简要介绍了动态共价键既具有普通共价键的高强度和稳定性,又能像分子间作用力（如氢键）那样可逆地断裂和重组的特点,以及基于动态共价键构筑智能凝胶材料的优势。综述了多种动态共价键,如芳香基苯并呋喃酮二聚体（diarylbibenzo furanone,DABBF）、三硫酯（trithiocarbonate,TTC）、芳基硼酸酯、酰腙键（acylhydrazone bond）、双硫键（disulfide bond）等的结构及其动态化学,以及应用它们合成聚合物凝胶的方法、凝胶的自愈合机理和性能。提出了发现和采用多种动态共价键构筑可自愈合聚合物凝胶的趋势,为此须解决多种动态共价键的相容性、凝胶自愈合机理与性能的光谱表征等问题,并加强应用研究。     

基于超分子化学方法制备自愈合聚合物材料的研究进展

本文综述了超分子化学方法制备自愈合聚合物材料的研究进展,着重介绍了利用氢键、π-π键、离子键等非共价键主-客体相互作用来制备自愈合聚合物材料的研究现状。     

基于Diels-Alder动态共价键的含PEGDE片段自修复环氧树脂性能研究

用含双烯体结构的呋喃甲胺,将硬段为双酚A型E-51环氧树脂(EP)和软段为PEGDE连接成线性大分子,并与含亲双烯体结构的双马来酰亚胺反应,制备出含热可逆Diels-Alder(DA)反应的软-硬-软结构的本征型自修复环氧树脂(EP-DA)。通过FTIR、DSC、TGA和电子万能试验机,对EP-DA结构和性能进行了表征。结果表明:DA动态共价键成功引入EP-DA,且DA正、逆反应的温度分别是60℃、122℃。当EP-DA链段中的PEGDE和EP含量各占50%时,其耐热性和拉伸强度达到最佳。EP-DA还具有良好的再加工性能和多次自修复性能,受损试样在60℃下修复4 h后,裂纹基本愈合,且第一次修复率可达88. 41%,同一试样经过三次修复后,其修复率仍可达68%以上。     

Radical crossover reactions of a dynamic covalent polymer brush for reversible hydrophilicity control

Reversible hydrophilicity control of a radically exchangeable polymer brush with dynamic covalent linkages was successfully demonstrated. A polymer brush with alkoxyamine units was prepared via surface-initiated atom transfer radical polymerization, and reversible surface hydrophilicity control was achieved via dynamic covalent exchange reactions of alkoxyamines. Exchange reactions between alkoxyamine units in the side chains of the polymer brush and the terminal of poly(4-vinylpyridine) (P4VP) were carried out in order to prepare a side-chain functionalized polymer brush. Subsequent quaternization of P4VP chains with iodomethane was carried out to prepare a more hydrophilic surface. In addition, a de-grafting reaction of the quaternized P4VP side chains was performed to confirm reversibility of the alkoxyamine via radical exchange reactions on the surface. All the composition and wettability changes were investigated via X-ray photoelectron spectroscopy and contact angle measurements.     

Electrically conductive self-healing polymer composite coatings

The goal of the research described herein is the fabrication and assessment of electrically conductive partially-cured epoxy coatings which, upon cracking, autonomously restore barrier, mechanical and electrical properties via a microcapsule based healing mechanism. Upon cracking, microcapsules in the crack path release the ‘healing’ solvent ethyl phenyl acetate (EPA), which locally swells the matrix, promoting crack closure and enabling the diffusion and subsequent reaction of the residual hardener in the vicinity of the crack. Two different self-healing coatings and two controls based on an electrically conductive epoxy resin with approximately 20% carbon nanotubes (CNTs) were fabricated. Electrochemical impedance spectroscopy was employed to evaluate the potential of the CNT and non-CNT containing encapsulated systems to restore relatively large cracks and thus restore the barrier function. An in situ electro-tensile test in a microscope revealed that electrical conductivity and mechanical properties were restored to 64% (±23) and 81% (±39) respectively, which correlated to crack closure. Under appropriate testing conditions the system showed successive damage-heal events in terms of electrical conductivity.     

自修复聚合物材料用微胶囊

Microcapsules with dicyclopentadiene (DCPD) as core material and urea formaldehyde resin as wall material used for making self-healing polymer material were prepared with the in-situ polymerization method. The effect of microcapsules on the fracture toughness of epoxy resin was studied. The addition of microcapsules into epoxy resin results in the decrease of fracture toughness. When microcapsule content was kept constant, as the microcapsule size increased the fracture toughness of the epoxy resin decreased linearly and the percentage of decrease compared to the neat epoxy without microcapsules increased linearly. Moreover, the fracture toughness of the material decreases linearly with the increase of microcapsule content.     

高分子聚合物复合材料的自愈合研究进展

从自愈合机理出发,综述了高分子聚合物复合材料自愈合的研究进展,展望了其应用前景。     

Aminoglycoside hydrogels based on dynamic covalent bonds with pH sensitivity,biocompatibility, self-healing,and antibacterial ability

Despite aminoglycosides (AGs) have superior antibacterial ability, all approved AGs by FDA are associated with adverse effects such as ototoxicity and nephrotoxicity. To solve these problems, AGs hydrogels based on dynamic covalent bond cross-linking were quickly prepared within 25 s by using AGs, aldehyde hyaluronic acid (A-HA), and adipic acid dihydrazide graft hyaluronic acid (HA-ADH) as materials. FT-IR, thermal analysis, and SEM results exhibited that A-HA/HA-ADH/AGs hydrogels were successfully synthesized with highly porous and interconnected network structure. The water absorption ratio of the hydrogels increased with the decreasing pH and temperature, indicating the hydrogels were pH- and temp-responsive. The pH-dependent degradation also demonstrated pH sensitivity of the hydrogels. Rheology and self-healing analysis assessment displayed that AGs hydrogels had good mechanical property, self-healing ability, and injectability. The hydrogels had no cytotoxicity to L929 cells and their hemolysis ratios were between 0.7% and 1.3%, which reached a nontoxic level. Most importantly, inhibition zones results demonstrated that the hydrogels had excellent and sustained antibacterial performance against Escherichia coli and Staphylococcus aureus. Therefore, A-HA/HA-ADH/AGs hydrogels are potential dressings for wound healing. Further plans including antibacterial and in vivo wound healing assays will be shown in the next work.     

A review on self-healing coatings based on micro/nanocapsules

Polymer coating systems are classically applied on a metal surface to provide a dense barrier against the corrosive species. Coatings are susceptible to damage in the form of cracks, which form deep within the structure where detection is difficult and repair is almost impossible. Major advances for automatic repairing of defects have been made in the present decade within the field of self-healing polymeric materials. One of the most significant types of smart coatings is self-healing coating, which has the ability to release encapsulated active agents in a controlled way. They can be employed to develop a new family of smart multifunctional coatings. Incorporating micro/nanocapsules in coating matrix provides release of repairing agent rapidly after triggering due to crack propagation in coatings and gifts the self-healing to the coatings. This review covers the effective parameters in synthesis of micro/nanocapsules, several approaches to fabricate self-healing coatings based on these capsules and disadvantages of embedding them in coatings matrix. Current comprehensive review also provides all the knowledge of self-healing coatings based on micro/nanocapsules to whom that are concerned with coatings and corrosion prevention.     

本征型自修复聚合物材料研究进展

回顾了自修复聚合物材料的研究现状,目前所采用的自修复方法主要包括外援型自修复（纳米粒子自修复、微胶囊自修复、空心纤维自身修复、微脉管自修复等）和本征型自修复（可逆共价键自修复、可逆非共价键自修复）,重点介绍了本征型自修复聚合物材料的最新研究进展,可逆共价键自修复是通过在体系中引入酰腙键、双硫键、N-O键、Dieal-Alder可逆反应等实现的,可逆非共价键自修复是借助于体系中的氢键作用、疏水作用、静电作用、离子作用、大分子扩散作用、金属配体作用等机理实现的,对它们的修复机理及研究现状进行了系统的阐述,展望了自修复材料潜在的应用领域,如高屋建筑、核材料贮存、生物医疗材料等。     

外援型自修复聚合物材料研究进展

综述了近年来自修复聚合物材料的研究进展,根据自修复过程是否需要外加修复剂,聚合物基复合材料自修复方法主要包括外援型自修复和本征型自修复。结合近几年最新研究成果,归纳了几种典型的外援型自修复方法,主要包括空心纤维自修复、纳米粒子自修复、微胶囊自修复（双环戊二烯修复剂体系、环氧树脂修复剂体系等）、微脉管自修复、碳纳米管自修复等,系统阐述了这几种自修复方法的修复机理、自修复体系特点及研究现状。展望了自修复材料的研究前景：优化和开发新的修复剂体系以提高修复效率、实现真正意义上的仿生材料。     

Design of room temperature high self-healing efficiency natural rubber based on ionic supramolecular network

The introduction of ion association is one of the most effective ap-proaches to achieve the self-healing behavior of rubber. However, most commercially availabl...     

本征型导电自修复材料的研究进展

综述了本征型(可逆共价键、可逆非共价键自修复)导电自修复材料的最新研究进展,并对他们的修复机理和材料的制备方法进行了系统的阐述,最后简要的分析了导电自修复材料目前存在的主要问题并展望了其发展方向。     

Evidence from infrared ellipsometry for covalent bonding at a polymer/polymer interface with relevance to "lock-up" in pressure-sensitive adhesive laminates

In a novel application, infrared spectroscopic ellipsometry is used to provide clear evidence for the formation of a covalent bond at a polymer/polymer interface. Specifically, there is evidence for the formation of a Si-O-C bond resulting from a reaction between the silyl (SiH) group of a poly(hydrogen methyl siloxane) crosslinker used in poly(dimethyl siloxane) and the carboxylic acid group of poly(acrylic acid). This covalent bond formation could explain the source of the "lock-up" that is sometimes found between acrylic pressure-sensitive adhesives and a silicone-coated release liner.     

From covalent bonding to coalescence of metallic nanorods

Growth of metallic nanorods by physical vapor deposition is a common practice, and the origin of their dimensions is a characteristic length scale that depends on the three-dimensional Ehrlich-Schwoebel (3D ES) barrier. For most metals, the 3D ES barrier is large so the characteristic length scale is on the order of 200 nm. Using density functional theory-based ab initio calculations, this paper reports that the 3D ES barrier of Al is small, making it infeasible to grow Al nanorods. By analyzing electron density distributions, this paper shows that the small barrier is the result of covalent bonding in Al. Beyond the infeasibility of growing Al nanorods by physical vapor deposition, the results of this paper suggest a new mechanism of controlling the 3D ES barrier and thereby nanorod growth. The modification of local degree of covalent bonding, for example, via the introduction of surfactants, can increase the 3D ES barrier and promote nanorod growth, or decrease the 3D ES barrier and promote thin film growth.