The controlled preparation of crystalline three-dimensional (3D) nanoparticles is attractive in polymer science due to the diverse topological structure and complicated chain folding mechanism of polymers. In this study, an intramolecular cyclization-induced self-assembly (ICISA) strategy is proposed to prepare water-dispersible crystalline 3D polyhedron nanoparticles taking advantage of the amorphous to crystalline transition during self-assembly promoted by the thermally triggered intramolecular cyclization reaction of an amorphous poly(amic acid) (PAA). Upon thermal treatment of the PAA in water, the rigid and crystalline polyimide (PI) blocks are generated in the backbone due to the unique intramolecular cyclization reaction feature of PAA, leading to the in situ flexible to rod-like chain and the amorphous to crystalline transition simultaneously, as well as the formation of crystalline polyhedron nanoparticles. Benifiting from the excellent stability of PI, the chain packing patterns of the polymer can be clearly observed by high-resolution transmission electron spectroscopy, which is further proved by computer simulations, demonstrating that the arrangement of polymer chains has a tilt angle of about 30° with a d spacing of 0.34 nm. This finding brings new insights into understanding the crystallization behavior of polymers and the facile preparation of crystalline 3D nanoparticles in water.

中文翻译：

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来自分子内环化诱导的无定形聚（酰胺酸）在水中自组装的结晶三维多面体纳米颗粒


由于聚合物的拓扑结构多样且链折叠机制复杂，结晶三维 （3D） 纳米颗粒的受控制备在聚合物科学中具有吸引力。在这项研究中，提出了一种分子内环化诱导的自组装 （ICISA） 策略来制备水分散的结晶 3D 多面体纳米颗粒，利用无定形聚（酰胺酸）（PAA） 的热触发分子内环化反应促进的自组装过程中的无定形到结晶转变。PAA 在水中热处理后，由于 PAA 独特的分子内环化反应特性，在主链中产生刚性和结晶性聚酰亚胺 （PI） 嵌段，导致原位柔性到棒状链和非晶态到结晶的转变，以及形成结晶多面体纳米颗粒。得益于 PI 的优异稳定性，高分辨率透射电子能谱可以清楚地观察到聚合物的链堆积模式，计算机模拟进一步证明了这一点，证明聚合物链的排列具有约 30° 的倾斜角，d 间距为 0.34 nm。这一发现为理解聚合物的结晶行为和在水中轻松制备结晶 3D 纳米颗粒带来了新的见解。