Mesogen-Free Supramolecular Liquid Crystalline State Formed by a Polyelectrolyte/Amphiphile Complex

The microstructure and phase transformation of a highly-branched polyethyleneimine/octadecanoic acid (PEI(OA) 1 . 0 ) complex were investigated using a combination of DSC, XRD, optical polarised microscopy and temperaturedependent FT-IR spectroscopy. A mesogen-free thermotropic liquid crystalline state was observed in a certain temperature region. The strong ionic interaction between -COO- (from OA) and -NH + 3 (from PEI) and the hydrophobic interaction between the alkyl side chains contributes to the formation of a thermotropic liquid crystalline structure.