Evolution of structure and properties of a liquid crystalline epoxy during curing

Abstract

The evolution of structure, and thermal and dynamic mechanical properties of a liquid crystalline epoxy during curing has been studied with differential scanning calorimetry (DSC), polarized optical microscopy, x‐ray scattering, and dynamic mechanical analysis. The liquid crystalline epoxy was the diglycidyl ether of 4,4′‐dihydroxy‐α‐methylstilbene (DGEDHMS). Two curing agents were used in this study: a di‐functional amine, the aniline adduct of DGEDHMS, and a tetra‐functional sulfonamido amine, sulfanilamide. The effects of curing agent, cure time, and cure temperature have been investigated. Isothermal curing of the liquid crystalline epoxy with the di‐functional amine and the tetra‐functional sulfonamido amine causes an increase in the mesophase stability of the liquid crystalline epoxy resin. The curing also leads to various liquid crystalline textures, depending on the curing agent and cure temperature. These textures coarsen during the isothermal curing. Moreover, curing with both curing agents results in a layered structure with mesogenic units aligned perpendicular to the layer surfaces. The layer thickness decreases with cure temperature for the systems cured with the tetra‐functional curing agent. The glass transition temperature of the cured networks rises with increasing cure temperature due to the increased crosslink density. The shear modulus of the cured networks shows a strong temperature dependence. However, it does not change appreciably with cure temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2363–2378, 1997

Influence of liquid crystalline ordering on the properties of selected cured nematic epoxy materials

“…Gelation is thereby independent of liquid crystalline phase as well as cure temperature. In other studies it has been generally found that reaction kinetics is enhanced in more ordered phases (Guymon and Bowman, 1997;Liu et al, 1997;Mormann and Brocher, 1999) and that the network formation tends to stabilize more ordered phases (Lin et al, 1997;Shiota and Ober, 1997). However, there are also examples in which the network formation destabilizes the liquid crystalline phase (Gavrin and Douglas, 2001;Osada et al, 1996).…”

Kinetics of Epoxy–Amine Curing Accompanied by the Formation of Liquid Crystalline Structure

“…Robinson et al [7] studied curing of the same epoxy monomer, DOMS, with methylene dianiline (MDA), SAA, and BSA and showed that curing is accompanied by a phase transition. Lin et al [8] examined the evolution of the LC structure and the thermal properties in the systems DOMS-SAA and DOMS-aniline adduct with DOMS. The aforementioned studies use a LC monomer (DOMS), which develops the monotropic LC phase on cooling.…”

Curing Reaction and Phase Change in a Liquid Crystalline Monomer

“…It was also reported that the overall curing reaction kinetics is strongly affected by the presence of a LC phase. E. Amendola, [7] J. P. Liu, [8] Q. G. Lin [9] and A. A. Robinson [10] et al studied the curing reaction of the diglycidyl ether of 4,49-dihydroxy-a-methylstilbene with amine, and found an unusual exothermic double peak and that birefringent textures were developed during isothermal cure as the reaction proceeded.…”