Phase transformations of a liquid crystalline epoxy during curing

Abstract

The phase transformations of a novel liquid crystalline epoxy, digiycidyl ether of 4,4'-dihydroxy-~tmethylstilbene (DGEDHMS), from isotropic phase to liquid crystalline phase during curing have been studied using a cross-polarized optical microscope equipped with a hot-stage. Time-temperaturetransformation (TTT) diagrams were constructed following the isothermal curing of the DGEDHMS in the isotropic phase with a difunctional amine, the aniline adduct of the DGEDHMS, and a tetrafunctional sulfonamido amine, sulfanilamide. Our results show that curing with the difunctional amine results in a nematic-like texture, while curing with the tetrafunctional sulfonamido amine leads to a smectic-like texture. Furthermore, curing with the difunctional amine gives rise to a faster development of the liquid crystalline phase, but with a less stable mesophase as compared to the tetrafunctional curing agent. These results are explained in terms of intermolecular interaction and the chain conformation anisotropy resulting from the curing reactions. The TTT diagram will be useful for providing guidelines for processing these new liquid crystalline epoxy systems.

The effect of mesogenic length on the curing behavior and properties of liquid crystalline epoxy resins

“…Ober et al reported the synthesis, curing behavior and anisotropic mechanical properties of stilbene epoxy resins [1][2][3][4][5]. Yee et al investigated the morphology of stilbene epoxy resin and the effect of curing reaction on liquid crystallinity [6] Carfagna et al observed the isothermal curing behavior and morphological change of stilbene epoxy resin [7]. Mallon et al studied LCE resins with aromatic ester unit in the main chain [8].…”

“…Among these materials liquid crystalline epoxy (LCE) resins have gained considerable interest due to their advantages like controllable curing rate, high heat and chemical resistance and high mechanical properties. Epoxy resins with aromatic stilbene structure were investigated by many research groups [1][2][3][4][5][6][7][8]. Ober et al reported the synthesis, curing behavior and anisotropic mechanical properties of stilbene epoxy resins [1][2][3][4][5].…”

Effect of the network structure on thermal and mechanical properties of mesogenic epoxy resin cured with aromatic amine

“…In the field of epoxy fact that the mesogenic epoxy resins lose their thermosets, new types of epoxy resins which conliquid crystallinity with the progress of curing tain the mesogenic groups in their backbone, such was also reported. 10,14 We have also investigated as biphenol-type, [1][2][3][4] stilbene-type, [5][6][7][8] phenylbenthe thermal and mechanical properties of an epzoate-type, [9][10][11][12] and azine-type 13 resins, have been oxy resin which includes the biphenol group as a reported of both theoretical and practical interest. mesogenic group.…”

Synthesis and improved mechanical properties of twin‐mesogenic epoxy thermosets using siloxane spacers with different lengths

“…LC epoxy thermosets contain rigid mesogenic groups in their backbone moiety of network chains, such as biphenyl, [9][10][11][12] stilbene, [13][14][15][16][17][18][19][20][21] azomethine, [22][23][24][25][26][27] ester, [28][29][30][31][32][33] azo, 34,35 and other, 36 which show excellent mechanical and thermal properties. LC epoxy thermosets contain rigid mesogenic groups in their backbone moiety of network chains, such as biphenyl, [9][10][11][12] stilbene, [13][14][15][16][17][18][19][20][21] azomethine, [22][23][24][25][26][27] ester, [28][29]…”