Department of Materials Science, University of Milano Bicocca, Via R. Cozzi 53, 20125 Milano, Italy.
J Am Chem Soc. 2011 Jun 15;133(23):8982-94. doi: 10.1021/ja201551n. Epub 2011 May 18.
Supramolecular self-assembly of a host molecule with selected blocks of triblock copolymers enabled the formation of inclusion 2D nanocrystals that connect consecutive copolymer chains. Indeed, the selective inclusion of ethylene oxide (EO) blocks in inclusion crystals and the phase segregation of PO blocks of poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EO(n)PO(m)EO(n)) triblock copolymers provide an efficient route to create alternated crystalline lamellae and amorphous layers, forming a well-organized material. The spontaneous formation of the supramolecular architectures was realized by a solvent-free mechanochemical approach or by thermal treatment of the copolymer and host (tris-o-phenylenedioxycyclotriphosphazene), as demonstrated by in situ synchrotron X-ray diffraction. The driving force for the fabrication of crystalline inclusion compounds with selected EO segments is based on the establishment of cooperative noncovalent intermolecular interactions, while steric effects prevent the formation of the inclusion crystal with the remaining PO blocks. The 2D (1)H-(13)C solid state and fast-(1)H MAS NMR provide direct evidence of the intimate interactions between the host and EO block and the topology of the block copolymer in the material. The large magnetic susceptibility generated by the aromatic host nanochannels surrounding the included EO chains was interpreted by ab initio calculations (HF-GIAO/DGDZVP) that carefully reproduce the chemical shifts associated with the effects of guest-host interactions. The theoretical calculations enable the measurement of short intermolecular distances between the host and the target block, demonstrating the existence of a diffuse network of multiple CH···π host-guest interactions that improve the robustness of the supramolecular architecture. The overall evidence enforces the strategy of combining the use of block copolymers and clathrate-forming molecules to fabricate organized materials through noncovalent interactions.
主体分子与嵌段共聚物的特定嵌段的超分子自组装使包含物二维纳米晶体的形成成为可能，这些晶体连接连续的共聚物链。实际上，在包含晶体中选择性地包含环氧乙烷（EO）嵌段以及聚（氧化乙烯- b-丙烯氧化物- b-氧化乙烯）（EO(n)PO(m)EO(n)）嵌段共聚物的 PO 嵌段的相分离提供了一种有效的途径来创建交替的结晶层和非晶层，形成组织良好的材料。超分子结构的自发形成是通过无溶剂机械化学方法或通过共聚物和主体（三邻苯二酚氧环三磷腈）的热处理来实现的，如原位同步辐射 X 射线衍射所证明的。用选定的 EO 段制造结晶包含物的驱动力基于建立协同的非共价分子间相互作用，而空间位阻效应阻止了剩余的 PO 嵌段形成包含晶体。2D (1)H-(13)C 固态和快速-(1)H MAS NMR 提供了主体和 EO 嵌段之间紧密相互作用以及材料中嵌段共聚物拓扑结构的直接证据。由围绕包含的 EO 链的芳香族主体纳米通道产生的大磁导率通过从头计算（HF-GIAO/DGDZVP）进行了解释，该计算仔细地再现了与客体-主体相互作用的影响相关的化学位移。理论计算能够测量主体和目标嵌段之间的短分子间距离，证明存在多个 CH···π 主体-客体相互作用的弥散网络，这提高了超分子结构的稳定性。总的证据加强了结合使用嵌段共聚物和笼形形成分子通过非共价相互作用来制造组织材料的策略。
