Ring motion glassy

From the various experimental investigations, it is clear that carbonate motions, as well as phenyl ring motions, are involved in the mechanical p transition of BPA-PC. The intermolecular contribution has been evidenced by several authors and the cooperative character of the motions has been pointed out. However, neither of the considered techniques can provide detailed information about the nature of intra- or inter-cooperativity occurring in the glassy state. 

Fig. 29. Observed and calculated 2H NMR spectra for the mesogenic groups of a) the nematic (m = 2), b) the smectic (m = 6) liquid crystalline polymer in the glassy state, showing the line shape changes due to the freezing of the jump motion of the labelled phenyl ring. The exchange frequency corresponds to the centre of the distribution of correlation times. Note that the order parameters are different, S = 0.65 in the frozen nematic, and S = 0.85 in the frozen smectic system, respectively...

Busselez et al. [56] used neutron scattering with H/D substitution labeling to examine the structure and dynamics of glassy PVP and water in hydrated PVP systems, from which they identified two types of water motion. Consistent with the earlier simulations, they obtained structural evidence for the existence of water clusters, nanosegregation of PVP side-groups, and swelling and disorder within ring nanodomains in the presence of water. The Q-dependence observed for the relaxation time of water molecules indicated that water relaxation was a diffusive-like process in water-rich domains while between water clusters subdiffusive motions prevailed. 

In the liquid crystalline phase, the local 180° jumps of the phenyl ring are augmented by diffusive rotation about the C2 axis by arbitrary angles as evidenced by the substantial narrowing of the NMR spectra. It is interesting to note that these two motional processes can be separated on cooling into the glassy state, where the diffusive rotation is frozen, whereas the 180° jumps persist as thermally activated local motions. ... 

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