A series of side chain liquid crystal polyurethanes (CnOMeP) with even-numbers of methylene units in the spacer was synthesised by the addition polymerisation of a -[bis(2-hydroxyethyl)amino]-v -(4-methoxyazobenzene-4 0 -oxy)alkanes (CnOMe-diol) with hexamethylene diisocyanate. The thermal and structural properties of CnOMeP were determined by means of polarising optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction. C2- and C4OMeP showed a completely amorphous nature, while C6– C12OMeP exhibited a bilayer smectic structure. Polyurethane backbones have a high tendency to crystallise. Crystallisation is closely related to hydrogen bonding between polyurethane groups. Short spacers favour an amorphous nature, while longer ones tend to lead to crystallisation. In order to obtain further information concerning backbone crystallisation, Fourier transform infrared spectroscopy (FT-IR) studies of CnOMeP polyurethanes were carried out at different temperatures focusing on the H-bonds between the N–H and CyO groups of the polyurethane backbone.
Посилання на статтю:
Hard segmented side chain liquid crystal polyurethanes with azobenzene mesogenic moieties / Marko Brecl, Majda Žigon // Polymer. – 1999. – N 40. – P. 6529–6538.