LIGHTLY CROSS-LINKED LIQUID-CRYSTALLINE EPOXY-RESINS - THE EFFECT OF RIGID-ROD LENGTH AND APPLIED STRESS ON THE STATE OF ORDER OF THE CUREDTHERMOSET

Lightly crosslinked liquid crystalline epoxy resins were synthesized b y reacting rigid rod epoxy-terminated molecules with decanedioic acid (SA). The obtained networks exhibited a smectic phase even in the case of 2,6-bis(2,3-epoxypropoxy)naphthalene, whose aspect ratio is very l ow. Upon application of uniaxial stress, a smectic phase was surprisin gly obtained also for the system obtained by reacting p-bis(2,3-epoxyp ropoxy)benzene (QH), whose aspect ratio is practically equal to one, a nd SA. Stretching of the smectic samples above the glass transition te mperature determines orientation of polymer chains, yielding considera bly high values of the order parameter S. Thermomechanical analysis sh owed, for one of these systems, that stretching induces a shift of the isotropization temperature to higher values.