The effects of carbon nanofibre on the liquid crystalline behaviour and cholesteric pitch of aqueous solutions of hydroxypropyl cellulose

Abstract

The liquid crystalline behaviour of aqueous solutions of hydroxypropyl cellulose (HPC_aq.) in which a small amount of carbon nanofibres (CNF) are dispersed (HPC_ aq./CNF) was investigated. Small spherical anisotropic droplets showing a biphasic state were found in the sample in which f ₂ = 45.8 wt%, where f ₂ is the weight fraction of HPC and CNF based on the total solids content. A preferential interaction is suggested between the hydrophobic surfaces of CNF and the spherical anisotropic droplets, or domains, of HPC. The samples of HPC_aq./CNF with f ₂ lying between 59.4 wt% and 67.3 wt% showed the iridescence characteristic of the cholesteric phase. It was found that the cholesteric pitch multiplied by the averaged refractive index of HPC_aq./CNF was shorter than that of HPC aq. at a given value of weight fractions f ₁ and f ₂, where f ₁ was the weight fraction of polymer based on the weight of the solution alone.

Keywords:

• Hydroxypropyl cellulose
• aqueous solutions
• carbon nanofibre
• cholesteric pitch
• reflection spectra

Acknowledgements

We are grateful to Dr T. Adachi (TOSOH Analysis and Research Centre Company, Ltd.) for the thermo-gravimetric measurements and FTIR microspectroscopic analysis. We are also grateful to Professor T. Ito (Kyoto Institute of Technology) for the preparation of carbon layers on the glass slides.