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Phase behavior and structure in mesogen containing polyurethanes
Author(s) -
Macknight W.J.,
Papadimitrakopoulos F.
Publication year - 1993
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19930690107
Subject(s) - mesophase , mesogen , differential scanning calorimetry , crystallography , liquid crystal , materials science , glass transition , infrared spectroscopy , thermotropic crystal , crystal (programming language) , polymer chemistry , chemistry , organic chemistry , composite material , polymer , liquid crystalline , physics , optoelectronics , computer science , thermodynamics , programming language
Abstract The mesophase to crystal phase transition observed upon heating the monotropic liquid crystal polyurethane (2,6‐LCPU‐6), based on the mesogenic biphenol 4,4′‐bis(6‐hydroxyhexoxy)biphenyl (BHHBP) and 2,6‐toluenediisocyanate (2,6‐TDI), has been investigated by differential scanning calorimetry (DSC), wide angle x‐ray scattering (WAXS) and infrared (IR) spectroscopy. Hexafluoroisopropanol (HFIP) fast solvent‐evaporation casting resulted in 2,6‐LCPU‐6 thin films with a glassy mesophase morphology. The mesophase to crystal exothermic transition has been observed by DSC between 130 and 140°C, depending on sample preparation. It is accompanied by a substantial increase of H‐bonding between urethane C=O and N‐H, as observed by IR. Curve fitting analysis of the conformationally sensitive amide I region revealed three bands; ordered H‐bonded carbonyl groups, disordered H‐bonded carbonyl groups, and “free” carbonyl groups. The prime feature of the 130°C transition is the substantial increase of ordered H‐bonded carbonyl groups at the expense of disordered H‐bonded carbonyl groups. Crystal melting occurs between 180 and 210°C and is accompanied by the complete disappearance of the ordered H‐bonded peak along with substantial changes in the frequency and width at half‐height of the disordered H‐bonded peak