Synthesis and properties of liquid crystalline polyurethane elastomers

✍ Scribed by Tae-Jung Lee; Dong-Jin Lee; Han-Do Kim

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 259 KB
• Volume: 77
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(20000718)77:3<577::aid-app13>3.0.co;2-x

✦ Synopsis

Novel type of mesogenic chain extenders used in this study are N,NЈ-bis(4hydroxyphenyl)-3,4,3Ј,4Ј-biphenyldicarboxyimide (BPDI) and N, NЈ-bis[4-(6-hydroxyhexyloxy) phenyl]-3,4,3Ј,4Ј-biphenyldicarboxyimide (BHDI). BHDI has a flexible spacer of 6-methylene units but BPDI does not. The liquid crystalline polyurethane elastomers were synthesized from BPDI or BHDI as a mesogenic chain extender, 4,4Ј-diphenylmethane diisocyanate, and poly(oxytetramethylene)glycol (MW 1000) as a soft segment. Polyurethane based on BHDI exhibited two melting transitions. However, any melting behavior was not shown in the BPDI-based polyurethanes because of higher melting temperature than decomposition temperature. The composition of polyurethanes was varied as a means of manipulating liquid crystalline behavior and physical properties. The BHDI-based polyurethanes containing above 50 wt % of hard segment content exhibited nematic liquid crystal behaviors. As the hard segment content of the BHDIbased polyurethanes increased, the glass transition temperature (T g ), strength, modulus, and the amount of hydrogen bonding increased.