Insulating materials with a low dielectric constant and a low dielectric loss are in high demand to meet requirements of the continuous miniaturization of electronic devices and high speed information transmission. We fabricated porous polyimide/reduced graphene oxide (PI/rGO) hybrid films with an ultralow dielectric constant and a low dielectric loss via a facile “blow-balloon” method. Poly­(ethylene glycol) (PEG) was used as a pore-forming agent by mixing with polyamide acid carboxylate (PAAC) and GO in water. The ternary mixture of PAAC/GO/PEG formed a hydrogel and dried naturally into a xerogel film. Porous PI/rGO films were obtained by in situ thermal pyrolysis of PEG through heating PAAC/GO/PEG hybrid films to 400 °C. The homogeneous porous structure could be regulated easily by adjusting the mass ratio of PEG to PAAC/GO. The porous structure inside the hybrid films prepared by the hydrogel method provided the PI/rGO films with an ultralow dielectric constant (κ) as low as 1.9 and a high ductility with an average elongation at break above 38%. This porous PI/rGO film with an ultralow κ value may be a promising candidate for next-generation interlayer dielectrics.

A fluorescent and robust superhydrophobic coating based on a fluorinated polypyrene/silica hybrid film was prepared readily on the large-scale substrates.

Polyimide/inorganics hybrid films fabricated by conventional approaches, including an in situ polymerization method, the sol–gel process, and a solution blending method, have a dramatic drop in malleability. In this work, a hydrogel strategy for preparing ductile polyimide/reduced graphene oxide (PI/rGO) nanohybrid films with internal porous structures has been proposed. The hydrogel strategy involved two steps. The polyamide acid carboxylate/GO (PAAC/GO) films were first prepared by tape casting, followed by a gelation process of the PAAC/GO aqueous solution; the PI/rGO films were then obtained after an imidization reaction of the PAAC/GO films. Interestingly, in this strategy, the PAA chains tended to self-assemble into microdomain crystalline structures assisted by their interactions with water, as revealed by XRD and Raman spectroscopy. The present PI/rGO films display more uniform microstructures, without aggregation of the rGO nanosheets. Furthermore, they exhibited an enhanced toughness property, with a high elongation at break of 37–55%. In addition, their dielectric property is more stable and less frequency-dependent due to the internal porous structure. This hydrogel strategy would appear to be a promising candidate for fabricating hybrid PI–inorganic composite materials, even other hybrid organic/inorganic composite materials with specific features.

A polyvinylidene fluoride (PVDF) membrane was modified by a low temperature plasma treatment and grafted with cross-linked collagen. The crosslinker of collagen was glutaraldehyde. The effects of glutaraldehyde concentration, crosslinking time and crosslinking temperature on membrane properties and surface structure were investigated. The properties of the modified membrane were characterized by the contact angle and pure water flux. The surface structure of the membrane dyed with an acid dye was observed by a polarizing microscope. The modified membrane was further characterized concerning permeability and adsorption capacity. Bovine serum albumin (BSA) was used as a model protein. The cell culture ability of the membrane was examined by the methyl thiazolyl tetrazolium (MTT) method. The amount of grafted collagen on the membrane surface reached the maximum when collagen was cross-linked with 0.4 wt% glutaraldehyde for 1 h at 35 C. The BSA adsorption capacity and cell culture ability examination indicated that the PVDF membrane grafted with cross-linked collagen had good hydrophilicity and biocompatibility.

This work shows the key role played by the chemical structure of polyimides in the thermal stability of birefringence.