Rigid rod networks: Liquid crystalline epoxy resins

Liquid crystalline polymers are well known for their unique mechanical and rheological properties. In recent years, some interest has been devoted to the study of a new class of liquid crystalline thermoset based on epoxy resins. Liquid crystalline epoxy resins can be obtained either by curing glycidyl terminated prepolymers over a range of temperature in which the mesophase is stable, or by reacting epoxy functionalized rigid monomers with a suitable curing agent. In our work this second approach has been followed. An unusual behaviour has been found for the form of the exotherm during the isothermal curing. Fracture toughness, Kq, was found to decrease with increased curing temperature. This experimental evidence has been correlated with the reduction of the extent of liquid crystalline character with temperature.