2H NMR orientational study of a probe dissolved in nematic solution and, used as crosslinker, in a liquid crystalline elastomer

The orientational order parameters, Szz and Biax, of UB-d4 [1,4-bis(undec-10-en-1-yloxy)benzene-d4] in the ZLI1167 nematic mixture are studied by means of 2H NMR at variable temperature. The Szz(T) trend fairly follows the Maier–Saupe theoretical curve; therefore, UB-d4 can be considered an excellent probe to monitor the ordering of the nematic phase itself, provided that Biax is not neglected and the complete analysis of quadrupolar and dipolar splittings is performed. UB-d4 is a typical crosslinker in liquid crystal elastomers (LCEs): the order parameters here collected help us to discuss the peculiarities of the crosslinker as a probe for the study of internal order in LCEs. From the analysis of our data and of data in the literature, we infer that the order parameter Biax of the crosslinker in the LCE matrix is low enough to be neglected without severely perturbing the determination of Szz. The crosslinker UB-d4 is a reliable probe to monitor the nematic order degree inside the LSCE-UB-d4 sample.