Various liquid crystalline bifunctional symmetrically and unsymmetrically s
ubstituted diepoxides based on the 4-(omega -oxiranyl-alkoxy)-benzoic acid
4-(omega -oxiranyl-alkoxy)-phenyl esters were synthesized. By modification
of the length of the flexible alkylene chains, the phase transition tempera
ture from the crystalline into the liquid crystalline state could be adjust
ed between 40 degreesC and 90 degreesC. The phase transition behavior of th
e monomers was examined by DSC. These diepoxides are capable to undergo pho
toinduced polymerization in the presence of a cationic photoinitiator with
intramolecular photosensitization in the liquid crystalline phase as well a
s in the isotropic phase. The photoinduced polymerization was monitored by
RTIR. For most monomers the rate constants for polymerization are higher in
the liquid crystalline state compared to the isotropic melt. A polymer net
work with liquid crystalline superstructure is formed if the polymerization
of the monomers is carried out in the liquid crystalline phase. No glass-t
ransition is measurable for the cross-linked materials, and the gel content
is about 96%. Although the polymers are highly cross-linked, they are not
brittle at all.