MACROSCOPIC AND LOCAL ORIENTATIONAL ORDERS IN NEMATIC GLASS

X-ray diffraction has been measured at different stages of the transit ion from a glassy to a partially ordered C1 phase of p-methoxybenzylid en-p'-n-butylaniline. The measurements were performed on oriented samp les for various orientations of the director of the liquid crystalline structure with respect to the scattering wave vector. The transition presents both a translational and an orientational ordering of the mol ecules. The variations of the macroscopic orientational order paramete r [P2] with the range of the molecular correlation length are reported . The change of [P2] at the transition is associated with a short-rang e orientational order in the glassy state. The dependence of the local orientational order parameter [P2(1)] upon the correlation length has also been determined and this is the first experimental demonstration of the interdependence of the orientational and positional order.