Condis Crystals of Flexible Macromolecules

But note the high temperature phases of polysiloxane (Sect. 4.7). Also a-polyamino acids may form lyodiilic liquid crystals after coil-to-helix transition to stiff-chain molecules held by intramolecular hydrogen bonds (see also Sect. S.3.4). 

The especially high mobility in the condis crystalline state was first discussed in the 1960 s based on the study of the mechanism of extended-chain crystal growth at elevated pressure from the melt A schematic drawing of the growth-front 

Conformational disorder in n-paraffms has been proposed for many years. A hexagonal so-called rotor phase has been found in a narrow temperature region below ultimate melting The n-paraffins with even numbers of carbon atoms show the rotor phase for 22 to 44 chain atoms, and with odd numbers of carbon atoms for 9 to 43 chain atoms . It was proposed that this rotor phase is also a condis phase. The importance of this condis phase of the paraffins lies not only in their being a model of the long chain molecules , but also in the relevance to the phase behavior in biologically important phospholipids .  

For polyethylene (dT/dp)j is larger than (dT/dp), i.e. the condis phase region widens with pressure, as can be seen in Fig. 4.1. For the n-paraffins the picture is reversed, the condis phase region shrinks with pressure, so that above about 300 MPa the paraffin condis phases are not stable any more . Initially this was taken as 

The high pressure condis phase of polyethylene could be observed down to a molecular mass of 65(K) For 1000 and 20W) molecular mass paraffins no condis phases were detected up to 1.5 GPa 

---