Low-k Polyimide Composite Materials Containing Hollow Mesoporous Silica Nanospheres

초록

Porous polyimide (PI) xerogels with amine functionalized hollow silica particle (AHSN) were synthesized via chemical imidization and freeze-drying. AHSN were mixed with poly(amic acid) of bis(4-aminophenyl)-1,4-diisopropyl benzene (BADB) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), which underwent chemical imidization to form porous low-k PI/AHSN hybrids. The porosity and microstructure of these materials were characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and dielectric analyzer. The addition of the AHSN particle of varied diameters and concentrations efficiently lowered and tuned the dielectric constant of porous PI xerogel. Using a BET apparatus and Bruggeman’s effect medium theory, the porosity and surface area of the PI/AHSN hybrid xerogel were measured, as well as the air content within the hybrid materials. The results showed that smaller AHSN particle reduced the dielectric constant of the hybrids more effectively because the larger surface area, as well as more functionalized groups on their surfaces, resulted in better interfacial interaction with the PI matrix, resulting in limited orientation and relaxation of polar groups located on the interfaces between PI and particle. The dielectric constant and dissipation factor at 10 GHz frequency of PI xerogel film co-operated with 10 wt.% of small size of AHSN was 1.151 and 0.001, respectively.