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Rheological properties of cholesteric liquid crystals as lubricant additives

A. Bindu Madhavi

Department of Physics, Acharya Nagarjuna University, Nagarjunanagar-522 510, India

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and

S. Sreehari Sastry

Department of Physics, Acharya Nagarjuna University, Nagarjunanagar-522 510, India

E-mail Address: sreeharisastry@yahoo.com

Corresponding author.

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https://doi.org/10.1142/S0217979219500140Cited by:3 (Source: Crossref)

Abstract

Rheological properties of Cholesteryl n-valerate, Cholesteryl decanoate and Cholesteryl myristate which are esters of cholesterol have been studied. Phase transition temperatures and rheological parameters such as viscosity, elastic modulus G $^{'}$ , loss modulus G $^{″}$ as functions of temperature, shear rate and time are investigated. In frequency sweep test, a higher transition crossover region has occurred for Cholesteryl myristate, whereas for Cholesteryl n-valerate a frequency-independent plateau prevailed for both the moduli. The occurrence of blue phase in Cholesteryl decanoate during temperature sweep measurements is an indication for the rheological support. The results for steady state have informed that cholesteric esters are having non-Newtonian flow behavior in their respective cholesteric phases. The power-law model has explained well the shear rate dependence of shear stress. A few practical applications of these esters as lubricant additives are discussed, too.

Keywords:

PACS: 61.30.-V, 62.20.Qp, 81.40.Pq, 83.50.Ax, 83.60.Bc, 83.80.Xz, 83.90.+s

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