Flow temperatures of transition from anisotropic to isotropic state

To interprete these X-ray spacings, let us first examine the structure of model compounds PMAA-n and PMMAA-n. The macromolecules of these polymers have a chemical structure similar to that of Pc5iMAA-n with the difference that they do not contain cholesterol groups in the side chains. 

On the basis of the obtained X-ray data, the structure of cholesterol-containing pol3rmers of the PChMAA-n series may be presented as follows. 

First of all, it is evident that the structU3 e of PChMA and PChMAA-2 differs from that of PChMAA-n where n 5. This difference msmifests itself both in the values of dj and the dependence of small-angle X-ray spacings d2, 4 

Another reason why it is difficult to discuss the structural model of cholesterol-containing pol pers is the fact that so far no adequately substantiated structural model of low-molecular cholesteric liquid crystals exists, apart from the already mentioned packing pattern proposed in Ref. (26), It seems that for a full understanding of the mesophase structure of cholesterol esters, one should, first of all, carefully study their crystalline structure. Such a study, described in Refs, (27, 28), has not yet lead to a complete description of molecular packing in cholesterol esters. 

Although the structure of cholesterol-containing polsrmers is not yet completely understood, there is no doubt that the liquid crystalline properties exhibited by these polymers are due to a particular oirder in the arrangement of cholesterol groups. This is corroborated by the results of studying the structure and optical properties of model compounds not containing cholesterol. The above-mentioned PMAA-n and PMMAA-n are optically isotropic in all three physical states vitrified, elastic and viscous. 

---

See also in sourсe #XX -- [ ]

---