Effect of Alkyl Chain Length on the Orientational Behavior of Liquid Crystals Nano-Film
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Different homologues of cyanobiphenyl liquid crystals (CB LC) (nCB with n = 5, 6, 7) present an interesting and novel material system. So far, their orientational behavior at nanoscale has not been extensively investigated yet. Here, we utilized a self-established in situ ball-on-disk testing platform equipped with polarized Raman spectroscopy, to study the ordering performance of nCB LCs confined as a nano-thin lubricating film. The results demonstrated that both external condition as shear velocity and internal molecular alkyl length dramatically affect the ordering process of nCB LC nano-lubricating film, consequently the degree of anisotropy. A simple model, along with detailed physical analysis, has been proposed to explain the observed phenomena. Our findings may provide new insights into controlling the alignment of LCs during lubricating.
KeywordsNanotribology Liquid crystal Nano-lubricating film Raman spectroscopy
The work was financially supported by the National Natural Science Foundation of China (51305225), the National Key Basic Research Program of China (2013CB934200), Research Fund of the Tsinghua University (20131089320).
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