  IR polarized spectroscopy was employed, to obtain the three components of IR
absorbance for a series DTC5Cn (n=5,7,9,11) of bent-shaped dimers containing
double fluorinated terphenyl core. Then, they were used to calculate both
uniaxial (S) and biaxial (D) order parameters, for various molecular groups of
dimers. The molecule bend was estimated due to observed difference between S
parameters for the terphenyl core and central hydrocarbon linker. It is found
to be significant in N phase despite almost no macroscopic director bend. The
temperature dependence of the order parameter, S, distinctly reverses its
monotonic trend of increase to decrease at the transition temperature, TN-NTB
to the NTB phase as result of the director tilt in the NTB phase. The biaxial
order parameter, D, is negligible in the N phase, and then starts increasing on
entering the NTB temperature, similarly to sin2q. The local director curvature
is found to be controlled by the molecular biaxiality parameter.
