Orientational and conformational order in RF PLCs

Small angle neutron scattering (SANS) experiments illustrate the drastic change in conformation occuring at the I-N transition and provide a measure of anisotropy of the radius of gyration and its increase with decreasing temperature across the nematic phase [26, 27]. The appearance of hairpin defects (abrupt changes in chain direction 

The events correlated with the I-N transition on cooling occur as a two-stage process [36, 39]. 

The phase transition itself, which involves molecular ordering and segregation of anisotropic chains without large scale migration across phase boundaries. This is controlled by nucleation and growth mechanisms. 

A second stage, which reveals strongly time dependent annealing, relaxation and phase separation (large scale demixing of isotropic and anisotropic domains) phenomena, as illustrated in subsequent sections. 

As will become apparent from the examples of influence of thermal history that are provided in sections 6,3-6.5, kinetic phenomena are manifest at both stages of the I-N transition. The mesophase, as initially formed, is removed from thermodynamic and/or morphological equilibrium. 

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