Side-chain liquid-crystalline polyacrylates: Experimental evidence of a coexistence of a double main-chain confinement inside the smectic layer

Detailed profiles providing the main-chain/mesogen organisation within the smectic layers have been deduced from neutron diffraction measurements, by combination of the coherent scattering length profiles of the fully hydrogenated and the partially deuterated side-chain liquid-crystal polymers. Two different sites of the molecule (either on the main chain or on the mesogen extremity) have been labelled to prove that main chains can occupy the! central zone of the mesogenic layers whereas most of them remains confined between the layers of mesogens. This surprising result can be explained considering symmetry arguments.