Viscoelasticity liquid crystalline elastomers

Zanna JJ, Stein P, Marty JD, Mauzac M, Martinoty P. 2002. Influence of molecular parameters on the elastic and viscoelastic properties of side chain liquid crystalline elastomers. Macromolecules 35 5459 5465. 

After Gerhard Wegner had left Freiburg to become the co-founder and director of the Max Planck Institute for Polymer Research in Mainz, Heino Finkelmann joined the Institute in 1984. In his research, Heino Finkelmann successfully combined the anisotropy of liquid crystals with the viscoelasticity of polymers [26]. This led him to the discovery of new generations of liquid crystalline elastomers, tunable lasers, and stimuli-responsive smart macromolecular materials. 

The possibility for the existence of mesophase in a rubbery state 36,46), typical only for macromolecular compounds with their natural ability to display big reversible deformations, reveals interesting prospects from the viewpoint of creation of new types of liquid-crystalline materials in the form of elastic films, as well as for development of the theory of viscoelastic behaviour of such unusual elastomers. 

E. Shiva Kumar, C. Das, K. Banik, and G. Mennig. Viscoelastic properties of in situ composite based on ethylene acrylic elastomer (AEM) and liquid crystalline polymer (LCP) blend. Compos. Sci. Tech., 67(6) 1202-1209, May 2007. 

Shivakumar E, Das C, Segal E, Narkis M. Viscoelastic properties of ternary in situ elastomer composites based on fluorocarbon, acrylic elastomers and thermotropic liquid crystalline polymer blends. Polymer 2(X)5 46(10) 3363-71. 

The possibility of the existence of the mesophase in a highly elastic state characterized by the capacity of the polymer to exhibit large reversible deformations offers interesting prospects for the creation of new types of liquid-crystalline materials in the form of elastic films and is interesting for elaborating a theory of the viscoelastic behavior of unusual LC elastomers [14]. 

Materials with molecular networks, such as cross-linked elastomers and crystalline polymers, do not flow and so are classified as viscoelastic solids. Shear stresses do not decay to zero with time, ie, equilibrium stresses can be supported. Above Tg, such amorphous materials are still classified as solids, but most of their physical properties such as thermal expansivity, thermal conductivity, and heat capacity are liquid-like. 

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