Mesogenic groups phase equilibria

The first group includes liquid-crystalline systems based on polymers containing mesogenic groups in the main chain wh they alternate with flexible firagments, or in the side chains where they are joined to the main chain by flexible spacers. Phase equilibrium between these systems is due to thermal transitions from the crystalline state to some type of liquid-crystalline phase and subsequently to an isotropic melt. 

However, it was recently found that many flexible-chain polymers containing no mesogenic groups are capable of forming thermotropic ordered phases in thermodynamic equilibrium and intermediate in structure and properties between crystalline and amorphous without any additional orienting effect of external fields. 

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