Abstract
The flexible aliphatic chains which have high chain mobility in the low temperature region were introduced into the backborn portion of the biphenol type and the bisphenol-A type epoxy resins. Thus, the former system showed very high elongation and toughness in the low temperature region. In this system, the colored pattern based on the birefringence was clearly observed in the vicinity of fracture surface. This means that the high toughness of this epoxy system in the low temperature region is attributed to the orientation of network chains, containing the mesogenic group, along the direction of the external force. The orientation is due to the planar structure of the mesogenic group and the high chain mobility of the flexible aliphatic chains in the glassy region.
