Functionalized mesoporous silica liquid crystal epoxy resin composite: an ideal low-dielectric hydrophobic material

The field of microelectronic devices and 5G communication has an increasing demand for polymer composites with low dielectric constant, low dielectric loss, and good hydrophobicity. However, traditional polymer composites cannot simultaneously satisfy them, which severely hinders their application. In this work, a liquid crystal epoxy resin (LCE4) consisted of a flexible chain and rigid mesogenic unit was prepared and cured with methylhexahydrophthalic anhydride (MHHPA). And the mechanism of the curing reaction and the phase structure of the liquid crystal epoxy resins were investigated. In addition, dielectric hydrophobic liquid crystal epoxy nanometer composite materials were successfully prepared with functionalized mesoporous silica (SBA-15) as a filler. The results showed that pure LCE4 exhibited excellent dielectric properties and thermal stability. Compared with pure LCE4, the composite material for SBA-15 modified with KH560 displayed lower dielectric constant, lower dielectric loss, higher glass transition temperature, and better hydrophobicity. For example, with a 0.5 wt% SBA-15, the dielectric constant and dielectric loss of the composite material were as low as (2.35, 0.025) compared with pure LCE4 (3.25, 0.036) that was reduced by 24.7% and 31%. In addition, the glass transition temperature and water contact angle are increased by 16 °C and 14°, respectively. Composites also showed good thermal stability and mechanical properties. The reasons may mainly be derived from the internal structure of LCE4, the effective modification of mesoporous SBA-15 by KH560, and the excellent dispersion of organic and inorganic phases.