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Liquid crystalline networks from 1,4‐benzenedicarboxylic acid bis(4‐cyanatomethylphenyl) ester
Author(s) -
Shiota Atsushi,
Körner Hilmar,
Ober Christopher K.
Publication year - 1997
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1997.021980924
Subject(s) - mesophase , oligomer , monomer , polymer chemistry , trimer , curing (chemistry) , materials science , glass transition , diketene , chemistry , phase (matter) , polymer , dimer , organic chemistry , composite material
The phase behaviour and curing reaction of 1,4‐benzenedicarboxylic acid bis(4‐cyanatomethylphenyl) ester (LC dicyanate) as well as the mechanical properties of the LC network were examined. The overall reaction kinetics were found to be first order with an activation energy of 67.5 kJ/mol similar to many conventional dicyanate monomers. Gelation was detected by viscoelastic measurements and occurred at a conversion of ≈0.5. These results suggest that the topology of the network formed in the LC dicyanate system was the same as non‐LC dicyanates such as 2,2‐bis(cyanatophenyl)propane. The onset of the mesophase was found to start at a conversion of ≈0.06 and end at a conversion of ≈0.20, independent of the curing temperature (180–280°C). This observation indicates that small clusters comprising a small oligomer (mainly trimer) surrounded by 6–7 monomers dominate formation of the mesophase which possesses a clearing temperature above at least 280°C. Competition between liquid crystalline order and high crosslink density resulted in a large free volume in the glassy state. This large free volume strongly affects mechanical behavior as well as the glass transition temperature of the LC network.