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Tube-graft-Sheet Nano-Objects Created by A Stepwise Self-Assembly of Polymer-Polyoxometalate Hybrids

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journal contribution
posted on 19.01.2016, 00:00 authored by Jing Tang, Xue-Ying Li, Han Wu, Li-Jun Ren, Yu-Qi Zhang, Hai-Xia Yao, Min-Biao Hu, Wei Wang
In this work, we report the preparation of complex nano-objects by means of a stepwise self-assembly of two polymer-polyoxometalate hybrids (PPHs) in solution. The PPHs are designed and synthesized by tethering two linear poly­(ε-caprolactone)­s (PCL) of different molecular weights (MW) on a complex of a Wells-Dawson-type polyoxometalate (POM) cluster and its countraions. The higher MW PCL–POM self-assembled into nanosheets, while the lower MW PCL–POM assembled into nanotubes just by altering the ratio of water in the DMF–water mixed solvent system. The two nano-objects have a similar membrane structure in which a PCL layer is sandwiched by the two POM-based complex layers. The PCL layer in the nanosheets is semicrystalline, while the PCL layer in the nanotubes is amorphous. We further exploited this MW-dependence to self-assemble the nanotubes on the nanosheet edges to create complex tube-graft-sheet nano-objects. We found that the nanotubes nucleate on the four {110} faces of the PCL crystal and then further grow along the crystallographic b-axis of the PCL crystal. Our findings offer hope for the further development of nano-objects with increasing complexity.