Birefringence studies on alkoxy benzoic acids with dispersed Fe₃O₄ nanoparticles

ABSTRACT

Synthesis, characterisation and order parameter studies of p-n-alkoxy benzoic acids 11oba and 12oba have been carried out along with 1–3wt% Fe₃O₄ nanoparticle (NP) dispersion separately. These nanocompounds are characterised by spectroscopic techniques such as polarising optical microscope, differential scanning calorimetry and scanning electron microscopy. The phase transitions can be easily identified by image processing methods with Matlab tool to reduce the costly equipment’s usage in finding the heat flow with respect to temperature. Further, the refractive index measurements are carried out using modified spectrometer for the liquid crystals (LCs) with the various concentrations of NPs at various wavelengths. It is found that the values of birefringence (δn) increase with increase in concentrations of NPs, and this shows that strong Vanderwaal’s interaction takes place due to well cappingbetween the NPs and LC molecules. The orientational order parameter has been determined from well-known theoretical molecular internal field models: Kuczynski method, effective geometry method and Haller’s extrapolation method. In all these methods, the order parameter found increases like birefringence with the dispersion of NPs. The increase in the birefringence δn values results in wide-angle vision, and thereby the LC nanocomposites are much useful in many optical display devices for various display applications.

Graphical abstract

KEYWORDS:

• POM
• SEM
• birefringence
• orientational order parameter
• Kuczynski method
• effective geometry method
• Haller’s extrapolation method

Acknowledgments

The author Dr R.K.N.R. Manepalli (Dr M. Ramakrishna Nanchara Rao) is thankful to UGC for grant 42-784/2013 (SR).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the University Grants Commission [42-784/2013 (SR).].