Morphology of the nematic phase

In the seemingly pure nematic phase there is an interesting difference between the broad line NMR spectra of polymers Pi and P5 (the latter both random and ordered). Below the biphase, in what appears as a homogeneosly birefringent liquid by optical microscopy (on the scale of c. 0.5 xm resolution), the broad line NMR spectrum of polymers P5 displays an I component indicative of fast isotropic motion, while none is observed in polymers Pi. As already mentioned, NMR cannot distinguish between phase and microphase separation and the presence of the isotropic component could be explained by one or more of the following four factors  

an actual N + I biphase, with isotropic droplets smaller than the resolution scale of microscopy dispersed in the mesophase matrix  

an unstable N phase, with a spatially uniform distribution of isotropic 

disclination defects, which form at the weld lines between coalescing 

local isotropic motion at the chain segment level. 

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