Synthesis, structure and phase behavior of liquid crystalline polyurethanes

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:7274101

Papadimitrakopoulos, F

This dissertation describes the synthesis, structure and phase behavior of polyurethanes based on the mesogenic biphenol 4,4'-bis (6-hydroxyhexoxy)biphenyl (BHHBP) and meta substituted tolylene/phenylene diisocynates. The structure-property relationships were determined as a function of hydrogen-bonding, the position of the methyl group in the tolylene diisocyanate moiety (TDI) and the biphenol moiety. The liquid crystalline phase (mesophase) and crystalline phase were investigated primarily with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and infrared spectroscopy. The influence of H-bonding on the structure and phase behavior of 1,4-LCPU-6 was determined by the synthesis of high molecular weight N-Methyl2,4-LCPU-65, using a novel high temperature polymerization of a biscarbamoyl chloride with the BHHBP mesogenic diol. In contrast to the regular ([alpha], [omega]-hexane diol) based polyurethanes (PUs), BHHBP derived polyurethanes (LCPUs) crystallize rapidly from their melts. Hexafluoroisopropanol fast solvent-evaporation casting or rapid cooling from the melt resulted in thin films or bulk samples with a glassy mesophase morphology. During the subsequent heating scan, the mesophase to crystal transition occurs. Highly oriented fibers were obtained for the mesogenic polyurethanes. Atomistic molecular simulations coupled with X-ray intensity refinement allowed determination of the crystalline chain conformation and packing characteristics for the 2,6-LCPU-6 and 1,3-LCPU-6 (2,6-TDI and 1,3-Phenylene Diisocynate (1,3-PDI) derived LCPUs). On the basis of structural similarity and well resolved WAXS powder patterns similar analysis was extended to the regular polyurethanes as well (2,6-PU-6 and 1,3-PU-6). The good correlation polymers suggest that melting is primarily controlled by the dissociation of H-bonds in the ordered domains.

• Research Organization: Massachusetts Univ., Amherst, MA (United States)
• OSTI ID: 7274101
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
POLYURETHANES
CRYSTALLIZATION
MICROSTRUCTURE
PHASE STUDIES
LIQUID CRYSTALS
STRUCTURAL CHEMICAL ANALYSIS
CRYSTALS
FLUIDS
LIQUIDS
MATERIALS
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHASE TRANSFORMATIONS
PLASTICS
POLYAMIDES
POLYMERS
SYNTHETIC MATERIALS
360602* - Other Materials- Structure & Phase Studies
360601 - Other Materials- Preparation & Manufacture