Thermotropic liquid-crystalline polymers having five-membered heterocycles as mesogens—2. Homo- and copolymers composed of 1,3- or 1,4-phenylenebis(1,3,4-thiadiazole 2,5-diyl) unit

✍ Scribed by Moriyuki Sato; Tomoaki Kamita; Kazue Nakadera; Ken-Ichi Mukaida

• Book ID: 103076535
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 462 KB
• Volume: 31
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(94)00150-2

✦ Synopsis

New homo-and copolyhydrocarbons composed of 1,3and/or 1 ,Cphenylenebis( 1,3,4-thiadiazole-2,5-diyl) units were successfully prepared by intramolecular cyclization of the corresponding polyhydrazides, which were synthesized by direct polycondensation of terephthalhydrazide and/or isophthalhydrazide with l,l&octadecanedicarboxylic acid, with diphosphorus pentasulphide in pyridine. Spectroscopical measurements, elemental analysis data and thermogravimetric analyses (TGA) suggested that the intramolecular cyclization completely proceeded. Differential scanning calorimetry (DSC) measurements, optical texture observation by means of polarizing microscope and powder X-ray analyses indicated that only the 1,4-phenylenebis(l,3,4-thiadiazole-2,5-diyl) unit-rich copolymer (80 mol.%) formed thermotropic liquid-crystalline smectic phase, but the others had birefringent or normal melts. The phase transition temperatures (melting and isotropization) had a tendency to change non-linearly with the 1,4_phenylenebisthiadiazole composition.