3 years ago

Effect of Topology and Composition on Liquid Crystal Order and Self-Assembly Performances Driven by Asynchronously Controlled Grafting Density

Effect of Topology and Composition on Liquid Crystal Order and Self-Assembly Performances Driven by Asynchronously Controlled Grafting Density
Rui Tan, Lincan Yang, Hongwei Ma, Pibo Liu, Siqi Zhu, Wei Huang, Heyu Shen, Li Han, Yang Li
A series of thermo-tunable liquid crystal block copolymers (LCBCs) with well-designed architectures were successfully synthesized. Linear/star poly[4-(4-vinylphenyl)-1-butene]-block-polybutadiene (PVSt-co-PB) moieties were obtained using living anionic copolymerization of 4-(4-vinylphenyl)-1-butene with butadiene, and topological [PVSt-co-PB]-LCBCs were generated through the adherence of mesogenic moiety via facile hydrosilylation. The PVSt LC block had well-defined grafting densities of approximately 100%, 70%, and 40%, whereas the PB LC block had an asynchronously tunable grafting density. This work included comprehensive studies on their self-assembly and yielded some interesting results. The influences of topologies and compositions on the phase transition behaviors and polarized optical performances of the resulting LCBCs that were driven by asynchronously controlled grafting density were carefully illustrated. The LCBCs with controlled molecular weight (MW) and narrow PDI showed wider LC phase ranges (ΔT) and a high tunability was added into the construction to aid thermos-responsive devices. The wide ΔT and high thermo-stability were demonstrated to be complementary between two LC blocks. However, the response-time and aggregation morphology in POM showed close similarity to LC blocks and showed a gradient in temperature-dependent changes with the PB LC block at a lower temperature and the PVSt LC block at a higher temperature. It is common for LC texture to change with varying temperature, whereas the gradient switching process was unique to LC blocks, which was further confirmed by temperature-dependent WAXD. In particular, the structural reorganization was determined to be driven by asynchronous grafting density by measuring the temperature-variation AFM, in that the asynchronous-tunable motion between LC blocks facilitates small phase separation.

Publisher URL: http://dx.doi.org/10.1021/acs.macromol.7b01952

DOI: 10.1021/acs.macromol.7b01952

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