Thermodynamic properties stressed glasses

Application of an electric field normal to the plates (typically the plates are coated with thin films of conducting glass such as indium-tin oxide) unwinds the helix if there is one, and also may cause the polar axis to orient normal to the plates (along the field), or even flatten the chevrons. It should be stressed that any added orientation of molecular dipoles along the field direction should be a weak secondary effect — the polar order occurring in the FLC phase is a thermodynamic property of the phase and not dependent upon applied fields. 

The goal of the work reported here was to devise a theory that predicts the polar/nonpolar phase separation as a favorable thermodynamic process. In addition, the effects of each of the physicochemical forms on the thermodynamic and structural characteristics of the biphasic material were sought. The current molecular model was not developed to predict mechanical or thermal behavior of ionomers. Hence, properties like glass transition and melt temperatures, storage, and shear moduli cannot be determined from the current model. We must also stress that this modeling work is still in its infancy. As such, it has used several tenuous assumptions that must be tested. The formalism is a start, but not the end, to devising a comprehensive treatment of ionomeric structure. 

A specific thermodynamic analysis is needed to derive expressions for the non-equilibrium properties of polymeric mixtures below the glass transition temperature. On the basis of the viscoleastic stress-strain relationship which has been considered in equation 3, specific relations may be obtained between equilibrium and nonequilibrium properties of the mixture. Indeed, when a mixture of one polymeric species and Np penetrant components is considered, the following balance equations for mass, energy and entropy may be written in local form, with respect to a polymer-fixed frame 11),... 

The properties of elastomeric materials are controlled by their molecular structure which has been discussed earlier (Section 4.5). They are basically all amorphous polymers above their glass transition and normally crosslinked. Their unique deformation behaviour has fascinated scientists for many years and there are even reports of investigations into the deformation of natural rubber from the beginning of the nineteeth century. Elastomer deformation is particularly amenable to analysis using thermodynamics, as an elastomer behaves essentially as an entropy spring . It is even possible to derive the form of the basic stress-strain relationship from first principles by considering the statistical thermodynamic behaviour of the molecular network. 

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