FTIR-spectroscopy on segmental reorientation of a nematic elastomer under external mechanical fields

Fourier transform infrared (FTIR) spectroscopy with polarized light is employed to study the segmental orientation and the order of a nematic liquid crystalline elastomers (NLCEs) with a monodomain structure in response to an external mechanical field. The reorientation and the order parameter of the different molecular moieties are analyzed in detail, revealing information about angular excursion in the rearrangement of the mesogens, the spacer molecules, and the main-chain. In case of an elongation of the NLCE films perpendicular to the initial mesogen orientation, no reorientation or change of order is observed for an elongation ratio less than 1.3. At higher strain, a molecular reorientation process is induced on all molecular segments and the order of alignment is decreased. When the NLCE-films are stretched parallel to the mesogens, no molecular reorientation takes place and the order parameters show no significant change.