Rheology of Liquid-Crystalline Polymers

The formation of lyotropic LCPs may be construed as the occurrence of a transition from an isotropic phase to an anisotropic phase. As early as 1949, Onsager (1949) predicted, on the basis of calculation of free energy, the formation of an anisotropic phase at a critical concentration of a solution when the aspect ratio of the molecule is sufflciently large. Several years later, using the concept of lattice in mixtures of polymer and solvent, Flory (1956) also developed a theory to predict, in terms of the aspect ratio of polymer molecule, the critical concentration at which the formation of an anisotropic phase is possible. This subject has been summarized in several review articles (Flory 1984 Grosberg and Khokhlov 1981 Papkov 1984). 

considerable efforts have been spent on the synthesis of thermotropic liquid-crystalline polymers (TLCPs), which spontaneously form ordered structures over a certain range of temperatures. Such polymers are very attractive to industry from the processing point of view because the problem of solvent recovery would not exist. 

Other TLCPs, such as copolyesters of HBA and 6-hydroxy-2-naththoic acid (HNA) (Calundann 1978, 1979, 1980), and copolyesters of 4,4 -bisphenol (or hydroquinone), terephthalic acid, and HBA (Cottis et al. 1972, 1976) have also been synthesized and commercialized. For instance, copolyesters consisting of HBA and HNA have the following chemical structure  

One can, however, synthesize thermally stable, semiflexible TLCPs that have a relatively low NI certainly much lower than the thermal degradation temperature (Ober et al. 1984). One such example is poly[(phenylsulfonyl)-p-phenylene-l, 10-decamethylene)-bis(4-oxybenzoate) (PSHQIO), with the chemical structure (Furukawa and Lenz 1986 Kim and Han 1993a)  

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Marrucci G, Guido S (1995) Shear flow rheology of liquid crystalline polymers. Int J Polym Anal Charact 1 191-199... 

RHEOLOGY OF LIQUID-CRYSTALLINE POLYMERS 457 in which use is made of the relationship... 

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