title: Evolution of helical mesostructures.
abstract: An intriguing evolution from a simple internal helix to a hierarchical helical (HH) mesostructure with both internal and external helices or a complicated screwlike and concentric circular (CC) mesostructure is successfully observed. The complicated helical structures are determined by TEM studies and 3D electron tomography. We demonstrate a topological helix-coil transition between the internal and external helices to reveal the origin of the HH mesostructure and the relationship between the straight helical and HH rods. Moreover, the boundary condition of the helix-coil transition is clarified to explain in detail the formation of complex helical structures, such as the screwlike mesostructure. It is proposed that the final structural characteristics are determined exactly by the balance between the decrease in the surface free energy and the maintenance of the hexagonal packing in one individual rod, which explains the formation of unusual CC, HH, and screwlike morphologies in one pot. Our success has opened new opportunities in the characterization of complex porous architectures, thus paving a way to remarkable advances in the fields of synthesis, understanding, and application of novel porous materials.
authors.affiliation: Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, 220 Handan Road, Shanghai, China.
authors.forename: Pei
authors.initials: P
authors.lastname: Yuan
authors.forename: Lingzhi
authors.initials: L
authors.lastname: Zhao
authors.forename: Nian
authors.initials: N
authors.lastname: Liu
authors.forename: Guangfeng
authors.initials: G
authors.lastname: Wei
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Wang
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Auchterlonie
authors.forename: J
authors.initials: J
authors.lastname: Drennan
authors.forename: Gao Qing
authors.initials: GQ
authors.lastname: Lu
authors.forename: Jin
authors.initials: J
authors.lastname: Zou
authors.forename: Chengzhong
authors.initials: C
authors.lastname: Yu