Synthesis and characterization of a novel liquid-crystalline epoxy resin combining biphenyl and aromatic ester-type mesogenic units

Epoxy Resins With Controllable "Thermally Conductive-Self-Healing" Synergies: a New Material to Meet the Needs of Flexible Electronic Devices

With the popularization of 5G technology and artificial intelligence, thermally conductive epoxies with self-healing ability will be widely used in flexible electronic materials. Although many compounds containing both performances have been synthesized, there is little systematic theory to explain the coordination mechanism. In this paper, alkyl chains of different lengths were introduced to epoxies to discuss the thermally conductive, the self-healing performance, and the synergistic effect. A series of electronic-grade biphenyl epoxies (4,4'-bis(oxiran-2-ylmethoxy)-1,1'-biphenyl (1), 4,4'-bis(2-(oxiran-2-yl)ethoxy)-1,1'-biphenyl (2), 4,4'-bis(3-(oxiran-2-yl)propoxy)-1,1'-biphenyl (3), and 4,4'-bis(4-(oxiran-2-yl)butoxy)-1,1'-biphenyl (4) were synthesized and characterized. Furthermore, they were cured with decanedioic acid to produce polymers. Results showed that alkyl chains can both affect the two properties, and the epoxies suitable for specific application scenarios can be prepared by adjusting the length of alkyl chains. In terms of thermal conductivity, compound 1 was a most promising material. However, compound 4 was expected to be utilized in flexible electronic devices because of its acceptable thermal conductivity, self-healing ability, transparency, and flexibility.

Synthesis of multifunctional liquid crystalline epoxy resin embedded cyclic-siloxane chain with Tg-less behavior and enhanced toughness

A novel tetrafunctional mesogenic epoxy monomer with a cyclic-siloxane chain as a central part was successfully synthesized and characterized by proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized optical microscopy. The transition temperature and liquid crystallinity of cyclic-siloxane type mesogenic epoxy were compared with those of linear-siloxane type mesogenic epoxy. Moreover, epoxy thermosets were prepared based on the cyclic- and linear-siloxane type mesogenic epoxy monomers and 4,4′-diaminodiphenylethane. The effects of epoxy backbone moiety on thermal and mechanical properties were investigated in detail. As a result, the cyclic-siloxane type mesogenic epoxy thermoset shows glass transition temperature-less behavior and low coefficient of linear thermal expansion without a decrease in toughness.