Description of the Mesophases

The various types of mesophases have usually been treated separately, and rarely did researchers review more than one mesophase at a time. One of the few descriptions of liquid and plastic crystals was given by Smith7). We will expand on this attempt and try to combine the description of all three major types of mesophase order, namely  

The term condis crystal , which is a contraction of the term conformationally disordered crystal , was coined to designate the most important mesophase for flexible, linear macromolecules. We are not aware of prior naming of this class of mesophases4. 

The melting process can be characterized by the entropy change on fusion8. Thermal analysis of fusion is illustrated in Fig. 1. We can break the overall entropy of fusion ASf into the three approximate parts positional, orientational, and conformational entropy of fusion 

4 The need ultimately to include conformational disorder in the system of mesophase materials has already been pointed out by Smith (Ref.7), p. 193) and becomes obvious when reading discussions of the behavior of typical condis crystals (see, for example, Ref.108)) 

Next is a group of materials with a mesophase which shows orientational disorder , but positional order. These materials are widely known as plastic crystals 16) because of the ease of deformation of such crystals. Again, this name is well accepted and much less cumbersome than orientationally disordered crystals7). 

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