High-resolution birefringence investigation on the effect of surface-functionalized CdSe nanoparticles on the phase transitions of a smectic — A liquid crystal

Abstract

The high-resolution optical birefringence study was carried out to experimentally study the impact of surface functionalized CdSe nanoparticles on the phase transitions of a smectic A liquid crystal 8CB (octylcyanobiphenyl). The birefringence data have then been used to probe the temperature variation of the nematic order parameter across both the nematic-isotropic (N − I) and the nematic-smectic A (N − SmA) phase transitions of 8CB + CdSe colloidal mixtures. With the inclusion of CdSe nanoparticles, both the N − I and the N − SmA phase transition temperatures have been observed to shift to lower temperatures as compared to the 8CB host, signalling the stabilization of the SmA phase. For 8CB + CdSe colloidal mixtures, the N − I transition is identified as weakly first order while the N − SmA transition remains continuous within the experimental resolution. From the detailed inspection of the optical birefringence data in close vicinity of the N − SmA transition, the upper limits for a possible latent heat for all colloidal mixtures have been derived. Also, the specific heat capacity critical exponent α values near the N − SmA transition for all compositions have been produced. it has been well established that the incorporation of CdSe nanoparticles to 8CB host leaves the N − SmA transition essentially bulk-like. A Landau-de Gennes type mean-field approach has also been used to describe our experimental data.