Liquid‐crystalline thermosets from mesogenic dimeric epoxy resins by tertiary amine catalysis

Abstract

Liquid‐crystalline thermosets (LCTs) were prepared by the curing of difunctional liquid‐crystalline dimeric epoxy monomers with imine moieties in the mesogenic core and central spacers of different lengths. Tertiary amines were used as catalysts in different proportions. The locked mesophases of the LCTs were characterized by polarized optical microscopy and wide‐angle X‐ray scattering and identified as smectic‐C, regardless of their smectic‐A or smectic‐C initial state. The influence of a 7.1‐T magnetic field on the macroscopic orientation of these materials was studied by dynamic mechanical analysis, and the orientation parameter was determined by IR dichroism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3916–3926, 2002

Curing behavior of Azo‐containing twin liquid crystalline epoxy resins with anhydride

“…All the LCTs from EnE/THPA have the nematic phase, because the large amount of anhydride hardener for complete cure brings too many distortions to form a smectic phase [25]. The twin LC epoxy resins show a different curing behavior from the single LC epoxy resins: the diffusion mechanism and chemical kinetic mechanism run through the curing process together.…”

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

“…43 The curing agent employed was 4, 4 0 -diamino-1, 2-diphenylethane (DDE; M w = 213; Kanto Chemical Co., Tokyo, Japan). An alkyl type twin-mesogenic epoxy monomer with the decyl group as a flexible chain was also synthesized (according to that previously reported) and used for comparison purposes.…”

“…[37][38][39][40] These study also clarified that the excellent mechanical properties of LC epoxy resin are caused by reorientation of the mesogenic groups during the fracture process or by the stiffness of LC domains that orient the mesogenic groups. [41][42][43][44][45][46] We previously reported that twin-mesogenic epoxy resins containing aliphatic spacers can be successfully synthesized to improve mechanical and bonding properties without causing a serious T g reduction of the epoxy thermosets with respect to the rigidity of two mesogenic groups. 39,40 However, there is a serious difficulty in preparing LC epoxy monomers during the thermoset process, and most LC epoxy monomers have a high melting point because of the high crystallinity derived from rigid mesogenic groups in the epoxy moiety.…”

Curing behaviors and kinetics of epoxy resins with a series of biphenyl curing agents having different methylene units

“…However, they also have low fracture toughness, and the incorporation of liquid crystalline structure is one of effectual way to make a modification. So recently, many studies have been focused on the subject of liquid crystalline thermosets due to their prior properties compared with ordinary epoxy resins, but most of these reports give the emphasis on the studies of liquid crystalline epoxy resins (LCERs) [4][5][6][7][8][9][10]. Well, as is known that curing agents can influence the structure of the networks, and the formation of LC phase in the networks can also be affected (even be determined) by the structure of the curing agents to crosslink the epoxy monomers.…”