Macromolecular liquid crystals

The formation of macromolecular liquid crystals usually seems to be virtually complete. Also, when the mesogenic group is sufficiently mobile, there is only little supercooling of the transition to the liquid crystalline state. Plastic and condis crystals, on the other hand, are expected to behave more like the fully ordered, macromolecular crystals, i.e., partial crystallinity is expected in these cases. 

Fig. 13. Schematic representation of macromolecular liquid crystals. A smectic structure is assumed for all cases...

The transition behavior of a number of liquid crystals with side-chain mesogens is summarized in Table 5. The most obvious feature of macromolecular liquid crystals is the frequent absence of fully ordered crystals at low temperatures. If fully ordered crystals are observed, crystallization is incomplete, i.e. the observed phase states are to be described by an area on the right side of Fig. 3. Glass transitions, which were hard to find in low molecular weight liquid crystals (see Table 3), are now prominent. 

Percec V (1997) From Molecular to Macromolecular Liquid Crystals. In Collings PJ, Patel JS (eds) Handbook Of Liquid Crystal Research, chap 8. Oxford University Press, Oxford... 

The distinction between macromolecular liquid crystals and condis crystals may be helped by experience, although the differences are usually only a matter of degree. Liquid crystals seem always to convert fully from the liquid state to the liquid crystalline state, and the conversion to the mesophase on cooling shows rdatively little supercooling (few kelvins). Condis crystals, in contrast, show more often than not partial conversion from the melt and a relatively high supercoolir (10 or more kelvins), i.e. they are much closer in their behavior to fully-ordered, macromolecular crystals. The crystallization kinetics of liquid crystals has foimd little attention in the past. It seems describable by Avrami expressions with exponents of 2 to 4 >. Condis crystals, in contrast, have in the few analyzed cases shown exponents of less than 2 2 W) tjie transition entropy of the liquid crystal to the isotropic melt is... 

J. L. White and J. F. Fellers, Macromolecular liquid crystals and their applications to high-modulus and tensile-strength fibers, J. Appl. Polym. Sci. Appl. Polym. Symp. 33, 137 (1978). 

Figure 9 Enthalpies of isotropization for three sets of main-chain macromolecular liquid crystals. The ordinate at zero number of CH2-groups indicates the mesogen contribution.

Soft condensed matter has played, and is expected to continue to play, an important role in this remarkable development. This paper focuses on the distinctive role that soft condensed matter, in the form of macromolecular liquid crystals and gels, plays in the manufacturing technologies of these strong polymer materials. In addition, a more specialized and recent example of the utilization of soft condensed matter in processing of intractable materials will be described, as well as an unusual method of synthesizing this remarkable class of matter. 

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