Liquid crystal thermosets. A new class of high-performance materials

ABSTRACT

The evolution of the liquid crystalline order during the cure of a reactive thermotropic liquid crystal (LC) is studied using two phenylethynyl-terminated biphenol and naphthalenediol model compounds. The nematic order in the melt of both model compounds at elevated temperature is monitored with X-ray Diffraction (XRD) and C-13 Nuclear Magnetic Resonance (¹³C NMR). XRD shows a cybotactic nematic phase; the global nematic order decreases with curing and eventually the resulting cross-linked liquid crystal thermoset (LCT) exhibits an isotropic morphology. The NMR method tracks the phenylethynyl end-group and yields data about the cure kinetics of this class of reactive LC mesogens. The observations may be used to make inferences about the cure behaviour and morphology of phenylethynyl-terminated random copolyester macromonomers.

Graphical Abstract

KEYWORDS:

• Thermoset
• liquid crystal
• nematic
• XRD
• NMR

Acknowledgments

We are indebted to Prof. Louis Madsen for fabricating the high temperature NMR probe and helpful discussions. We acknowledge Dr. D. Hermida-Merino (BM26 DUBBLE beamline of the ESRF) for support during XRD measurements and the staff of beamline BM28-XMaS (ESRF) for providing the superconducting magnet used in XRD experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.