Mean polarizability of molecules and anisotropy of the Lorentz tensor upon a nematic-smectic a phase transition: Their behavior in a homologous series

Experimental values of the mean polarizability of molecules, , and components of the Lorentz tensor, L j , in the nematic and smectic A phases are obtained for a homologous series of n -alkyl- p -(4-ethoxybenzylideneamino)-α-methylcinnamates. Dependences of the and L j values on the mesophase temperature, the orientational order parameter S of molecules, and the number n in the homologous series are revealed. The quadratic dependence of ( S ) in the nematic and smectic phases is established that is invariant with respect to the nematic-smectic A transition. Polarizability densities of the molecular core and the alkyl chain are found from the monotone decreasing dependence ( n )/ v (where v is volume per one molecule) in the smectic phase. The presence (or absence) of the odd-even alternation of L j ( n ) in the nematic (smectic) phase is shown. A monotone decrease in the Lorentz tensor anisotropy L with an increase in n is revealed in the smectic phase, and limiting values L j ( n → ∞) are determined.