Interface plasmon polariton and X-ray reflectivity of ultrathin films of ferroelectric main-chain liquid crystal polymers

We have carried out interface plasmon polariton (IPP) and specular X- ray reflectivity studies on two ferroelectric main-chain liquid crystal polymers based on polysiloxane (denoted as polysiloxane 1 and 2 respectively) with emphasis on the former. Films of thickness between 200 to 500Å were prepared by the spin-coating technique on silver films on glass substrates. We demonstrated spontaneous molecular self-assembly after the spin coating into a nearly perfect layered structure on these substrates for polysiloxane 1. The combined measurements allow the determination of the polymer dielectric tensor as a function of temperature and film thickness. The anisotropy of the dielectrics tensor, (ε_zz-ε_xx), strongly depend on the smectic order. It is thickness independent but depends on temperature and changes significantly across phase transitions. We discuss also the observation of "surface freezing" of few smectic layers at film- substrate interface far above the bulk smectic-isotropic phase transition of polysiloxane 1.