Effect of Various Diamines on the Mechanical, Thermal, and High-Frequency Dielectric Properties of Polyimide and Their Composites With Functionalized Hollow Silica Fiber

In this study, three different series of polyimides (PIs) and their composites fabricated using various chemical structure of diamines and functionalized hollow silica fiber (FHSF) were synthesized. The experimental results of three PIs indicate that the addition of fluorine atoms into the pending groups of PI can decrease the glass transition temperature (Tg) with increase in the chain flexibility and this can lower the dielectric constant of PI. The high-frequency dielectric constants of the composite materials decrease with increase in the loadings of FHSF. These phenomena are possibly accredited to the steric hindrance effect caused by the presence of trifluoromethyl groups of PI polymer chain and FHSF, which can interrupt the PI chain packing and increase their free volumes, resulting in the decrease of Tg and the dielectric properties of PIs. The high-frequency circuit transmission loss properties of fabricated composite materials measured using the Test Methods Manual IPC-TM 650 2.5.5.14 are lower than those of pure polymer matrix, recommending that the prepared materials could be selected as interlayer dielectrics for nano-level electronic.