Elastic deformations of nematic laterally attached dimers

Temperature dependences of the optical anisotropy and elastic constants of nematic laterally connected dimers, in which two rod-like 2,7-disubstituted fluorene moieties are linked through their 9-positions by flexible -OOC(CH 2)(m)COO- residues, were determined by using the Freedericksz method of thr eshold transitions in a magnetic field. It was shown that the possibility o f rotation of the mesogenic groups about their short axes influences the de pendence of the order parameter on spacer length. No marked dependence of s play and bend elastic constants on spacer length was observed. The results are compared with literature data for polymer and low molecular mass nemati cs.