Hectorite clay nanoplatelets effect on the electro-optical, dielectric, viscoelastic and ionic properties of 5CB nematic liquid crystal

Low concentrations (0.5, 1 and 2 wt%) of hectorite clay nanoplatelets dispersed in the nematic liquid crystal 5CB influence its electro-optical, dielectric, viscoelastic and ionic properties. In particular, a marked decrease of the threshold field of the Freedericksz transition and a faster electro-optical response are observed, with the most significant enhancement seen in doping with 1 wt% nanoparticles. This behaviour is associated with an increase in the dielectric anisotropy and the splay elastic constantK11, combined with a decrease in the rotational viscosityγ1. Dielectric spectroscopy in the low-frequency range reveals that the ionic properties are also affected by the presence of clay nanoplatelets. The variations of the ionic densityn and diffusion coefficientD suggest the occurrence of ion release or ion trapping phenomena related to the charged surfaces of the hectorite nanoplatelets. Partial aggregation of nanoplatelets occurs at higher concentrations.