NMR Investigations of Monodomains

While there are not many NMR investigations of the isotropic-nematic transition in sidechain liquid crystal elastomers [20, 21], they turned out to be crucial in answering the question whether strained LCEs show a first order phase transition with a classical two phase region or whether there is a continuous change of the local degree of nematic order, since one is in a state beyond the critical point. As already mentioned earlier in this section this question could not be settled conclusively with the mechanical and optical investigations described above. 

In Fig. 18 we show the H-NMR spectra of both an uncrosslinked linear liquid crystalline polymer and a monodomain elasto- 

It should be pointed out that, in addition to the built-in mechanical field discussed so far, there is also a contribution from finite size effects on the nematic-isotropic transition in liquid crystalline elastomers due to the finite average distance between cross-linking points. This question has been discussed, and it has been pointed out that varying the crosslinking density aids in disentangling these two different types of effects [20-22]. 

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