Screw dislocation-induced pyramidal crystallization of dendron-like macromolecules featuring asymmetric geometry |
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| Authors: | Xinyu Sun Xueyan Feng Xiao-Yun Yan Jiancheng Luo Ruimeng Zhang Tao Li Hui Li Jiahui Chen Fangbei Liu Ehsan Raee Stephen Z D Cheng Tianbo Liu |
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| Institution: | School of Polymer Science and Polymer Engineering, The University of Akron, Akron Ohio 44325 USA.; South China Advanced Institute for Soft Matter Science and Technology, School of Molecular Science and Engineering, South China University of Technology, Guangzhou 510640 China ; X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 USA ; Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb IL 60115 USA |
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| Abstract: | We report herein that dendron-shaped macromolecules ABn crystallize into well-ordered pyramid-like structures from mixed solvents, instead of spherical motifs with curved structures, as found in the bulk. The design of the asymmetric molecular architecture and the choice of mixed solvents are applied as strategies to manipulate the crystallization process. In mixed solvents, the solvent selection for the Janus macromolecule and the existence of dominant crystalline clusters contribute to the formation of flat nanosheets. Whereas during solvent evaporation, the bulkiness of the asymmetric macromolecules easily creates defects within 2D nanosheets which lead to their spiral growth through screw dislocation. The size of the nanosheets and the growth into 2D nanosheets or 3D pyramidal structures can be regulated by the solvent ratio and solvent compositions. Moreover, macromolecules of higher asymmetry generate polycrystals of lower orderliness, probably due to higher localized stress.The dendron-shaped macromolecules ABn crystallize into well-ordered pyramid-like structures from mixed solvents, which is on the contrary to spherical motifs with curved structures in bulk. |
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