Ductile Polyimide/Reduced Graphene Oxide Nanohybrid Films with Porous Structure Fabricated by a Green Hydrogel Strategy

Abstract

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.

Low Dielectric Constant Polyimide Hybrid Films Prepared by in Situ Blow-Balloon Method

“…Several tabular macropores parallel to the surface were visible in the PI/rGO-p 0 film when 2.0 wt % GO was used (Figure a, b). The formation of tabular macropores in the PI/rGO-p 0 may result because of hydrogen bonds between the GO and PAAC, which prevent the complete collapse of the hydrogel structure during drying . After PEG incorporation, the PI/rGO-p x film presented a porous character, as shown in Figure e–h.…”

“…The formation of tabular macropores in the PI/rGO-p 0 may result because of hydrogen bonds between the GO and PAAC, which prevent the complete collapse of the hydrogel structure during drying. 28 After PEG incorporation, the PI/rGO-p x film presented a porous character, as shown in Figure 4e Dielectric Properties of Porous PI/rGO-p x Films. After incorporation of porous structures, the dielectric constants of the PI/rGO-p x films decreased significantly with an increase in PEG content, which benefited from the low dielectric constant of air (κ = 1).…”

“…The incompatibility between the PI matrix and the inorganic filler is considered to be the main cause of the ductility deficiency of PI/inorganic hybrid films. − Microphase separation control of the PI matrix and inorganic filler are a key point in the preparation. In this work, a blow-balloon method was developed to produce porous PI/rGO films based on our previous study . The blow-balloon method introduced in this work is different from blow molding in the industrial process.…”

“…on our previous study. 28 The blow-balloon method introduced in this work is different from blow molding in the industrial process. First, graphene oxide (GO), poly(ethylene glycol) (PEG), and polyamide acid carboxylate (PAAC) were mixed in water to form a stable ternary blending system at 60 °C.…”

Studying Ni(II) Adsorption of Magnetite/Graphene Oxide/Chitosan Nanocomposite

“…However, the disadvantages of graphene sheets are that, in the water environment, they are poorly soluble and tend to aggregate, which significantly reduces the surface area and adsorption capacity. Thus, graphene oxide (GO), the intermediate product of oxidation of graphite, with many oxygen-rich functional groups (epoxy, hydroxyl, and carbonyl groups), is an attractive object for many research areas such as detection of DNA [3], matrix composite membranes, or film [4][5][6], especially in removal of heavy metal ions and organic pollutants from aqueous solutions. In recent years, a number of reports have been published on the adsorption of heavy metal ions by using GO and GO-based materials as an adsorbent.…”