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    星状嵌段偶氮苯类肽的自组装与光响应性

    Self-Assembly and Photo-Responsive Capacity of Star-Type Block Azopeptoids

    • 摘要: 星状聚合物因其独特的物理化学性质和拓扑结构而备受关注。然而,开发刺激响应型序列可控星状聚合物仍然是一项重大挑战。本文利用固相亚单体合成技术设计并制备了一种新型的具有特定序列结构、光响应性的两亲性星状嵌段偶氮苯类肽Star-(NAZO4-b-NME4-b-NCOOH)3,并通过溶液自组装制备了尺寸均一的球形胶束。由于偶氮苯基团的光致异构化特性,在紫外光和可见光的交替照射下,该球形胶束能够实现光控的尺寸可逆转变。此外,铂纳米颗粒修饰的球形胶束对硼氢化钠介导的4-硝基苯酚还原反应具有良好的催化能力和可逆的光控催化活性。此研究工作为刺激响应型序列可控星状聚合物的制备及其在纳米催化领域中的应用提供了理论指导。

       

      Abstract: Star polymers, as an appealing category of branched polymers, have garnered significant attention due to their distinctive physicochemical properties and topological configurations, demonstrating a variety of applications in biomedicine and nanotechnology. Nevertheless, the development of stimulus-responsive sequence-controlled star polymers remains a particularly formidable challenge. This paper reported the design and synthesis of a novel photo-responsive sequence-defined amphiphilic star-type block azopeptoids of Star-(NAZO4-b-NME4-b-NCOOH)3 using the solid-phase submonomer synthesis technique, where NAZO represented hydrophobic monomer of N-(2-azophenyl)ethyl glycine and NME represented hydrophilic monomer of N-(2-carboxyethyl) glycine, respectively. The subsequent molecular self-assembly of Star-(NAZO4-b-NME4-b-NCOOH)3 was carried out in the mixture of water and acetonitrile (volume ratio 1∶1), maintaining undisturbed at 4 ℃ to slowly evaporate the organic solvent. Consequently, uniform spherical micelles with an average diameter of approximately 20 nm were successfully formed. The photo-response behavior of these spherical micelles was thoroughly characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). An alternating irradiation with the ultraviolet (UV) and visible light resulted in a reversible diameter change toward the spherical micelles from approximately 20 nm to 10 nm, due to the photoisomerization feature of the azobenzene moiety. The carboxyl-modified amphiphilic star azopeptoids were utilized as building blocks to generate the functional spherical micelles, which could serve as the substrates to load the platinum nanoparticles for fabricating the organic-inorganic hybrid catalysts. As a proof-of-concept, the catalytic activity of the as-prepared hybrid nanocomposites was evaluated toward the borohydride-mediated reduction from 4-nitrophenol to 4-aminophenol, demonstrating a photo-controllable reversible and recyclable catalytic activity for several cycles. This work paves a significant route to fabricate stimulus-responsive sequence-controlled star polymers for the potential on nanocatalysis.

       

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