Self-Healing Supramolecular Block Copolymers
Self-Healing Supramolecular Block Copolymers
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DOI：
10.1002/anie.201204840
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发表时间：
2012-01-01
影响因子：
16.6
通讯作者：
Guan, Zhibin
中科院分区：
文献类型：
--
作者：
Hentschel, Jens;Kushner, Aaron M.;Guan, Zhibin
自发愈合损伤的能力是生物材料的一个关键特征，它增加了植物和动物的生存能力和寿命。相比之下，合成材料通常在损坏或断裂后失效。受自然界的启发，已经通过将机械[1]或光活化[2，3]愈合剂、可逆共价键、[4-7]金属配体络合物[8]和动态非共价键结合到聚合物中来开发了几种自愈合聚合物系统。[9-14]然而，向普遍适用和机械坚固的自修复聚合物的进展受到一个基本困境的阻碍：机械刚度/强度和快速大分子动力学（自发修复所需）通常具有反向依赖关系。[15因此，在具有高玻璃化转变温度（Tg）的聚合物中使用强可逆相互作用导致刚性但动态性较低的材料，[4，8]而在低Tg聚合物中的弱相互作用提供更多的动态愈合，但产生软材料。[9，17]为了解决这一难题，我们的实验室一直在探索聚合物的多相设计，将高模量和韧性与自发愈合能力相结合。[18]最近，我们报道了一种氢键刷状聚合物，自组装成一个硬/软两相系统，结合硬相的刚性和坚韧的机械性能与软基质中的动态超分子组装体的自修复能力。[18]与刷状聚合物不同，嵌段共聚物是重要的商品材料，其通过控制嵌段组成和长度表现出明确的多相形态和可调的机械性能。在嵌段共聚物中引入自修复能力将显著改善这一重要材料家族的性能并扩大其应用范围。在此，我们报告了一种用于新的多相自修复材料的超分子嵌段共聚物设计（图1）。我们推断，超分子嵌段共聚物应保留在常规共价嵌段共聚物结构中发现的硬/软两相形态，从而提供有利的机械性能（例如热塑性弹性体）。同时，位于软相中的超分子愈合基序应该保持动态和可逆，提供自愈合能力（图1）。408 C）作为软嵌段和聚苯乙烯（PS; Tg= ca. 1008 C）作为硬嵌段。以往的研究表明，共价PS-b-PBA-b-PS三嵌段共聚物具有微相分离的形态和独特的热塑性弹性体性能。[19]然而，这种共价体系的机械断裂将导致不可逆的共价键断裂和性能的永久损失（图1a）。我们推断，通过用动态四重氢键连接取代PBA软嵌段中心的共价键，超分子嵌段共聚物应该能够在机械损伤后自愈。为了证明这一点，我们合成了PBA-b-PS二嵌段共聚物末端官能化的一个明确的四重氢键基序，2-脲基-4-嘧啶酮（UPy）。UPy基序之间的二聚化导致形成超分子阿坝三嵌段共聚物，其中柔性PBA嵌段通过单个可逆UPy二聚体连接（图1b）。重要的是，这种结构将动态氢键相互作用放置在微相分离后两相系统的软相内，其中链运动应有助于…
The ability to spontaneously heal injury is a key feature of biological materials that increases the survivability and lifetime of plants and animals. In contrast, synthetic materials generally fail after damage or fracture. Inspired by nature, several self-healing polymer systems have been developed through the incorporation into polymers of mechanically [1] or photo-activated [2, 3] healing agents, reversible covalent bonds,[4–7] metal-ligand complexes,[8] and dynamic non-covalent bonding.[9–14] Nevertheless, progress towards generally applicable and mechanically robust self-healing polymers has been hampered by a fundamental dilemma: the mechanical stiffness/strength and rapid macromolecular dynamics (required for spontaneous healing) usually have an inverse dependent relationship.[15, 16] Thus the use of strong reversible interactions in polymers with high glass transition temperature (Tg) results in stiff but less dynamic materials,[4, 8] while weak interactions in low Tg polymers afford more dynamic healing, but yield soft materials.[9, 17] To address this dilemma, our laboratory has been exploring a multiphase design of polymers that combine high modulus and toughness with spontaneous healing capability.[18] Recently, we reported a hydrogen-bonding brush polymer that self-assembles into a hard/soft two-phase system, combining the stiff and tough mechanical properties of the hard phase with the self-healing capacity of dynamic supramolecular assemblies in the soft matrix.[18] Unlike brush polymers, block copolymers are important commodity materials exhibiting well-defined multiphase morphologies and tunable mechanical properties through the control of block composition and length. Introducing self-healing capability into block copolymers would significantly improve the performance and expand the scope of applications for this important family of materials. Herein, we report a supramolecular block copolymer design for new multiphase selfhealing materials (Figure 1). We reasoned that the supramolecular block copolymer should retain the hard/soft twophase morphology found in conventional covalent block copolymer architectures, affording advantageous mechanical properties (such as thermoplastic elastomeric). Meanwhile, the supramolecular healing motifs located within the soft phase should remain dynamic and reversible, providing selfhealing capability (Figure 1).To demonstrate our concept, we chose a block copolymer system having poly (n-butyl acrylate)(PBA; Tg= ca. À408C) as the soft block and polystyrene (PS; Tg= ca. 1008C) as the hard block. Previous studies have shown that covalent PS-b-PBA-b-PS triblock copolymers exhibit microphase-separated morphology and unique thermoplastic elastomer properties.[19] However, mechanical fracture of this covalent system would result in irreversible covalent bond rupture and permanent loss of properties (Figure 1a). We reasoned that by replacing the covalent linkage in the center of the PBA soft block with a dynamic quadruple H-bonding junction, the supramolecular block copolymer should be able to self-heal after mechanical damage. To demonstrate this, we synthesized PBA-b-PS diblock copolymers end-functionalized with a well-defined quadruple H-bonding motif, 2-ureido-4-pyrimidinone (UPy). Dimerization between UPy motifs leads to the formation of supramolecular ABA triblock copolymers with the flexible PBA blocks connected by a single reversible UPy dimer (Figure 1b). Importantly, this architecture places the dynamic H-bonding interaction within the soft phase of the two-phase system after microphase separation, where chain motion should facilitate …