Formation of Superhydrophobic Microspheres of Poly(vinylidene fluoride– hexafluoropropylene)/Graphene Composite via Gelation

Abstract

We report on the spontaneous formation of superhydrophobic poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/graphene composite microspheres with uniform size via gelation. When the suspension of PVDF-HFP/graphene (0.25 wt. % with respect to PVDF-HFP) in DMF adsorbs water vapor, it changes to a hybrid gel. A dried porous gel is obtained after solvent exchange and freeze drying. Morphology characterization shows that this hybrid gel is composed of PVDF-HFP/graphene microspheres with a diameter of 8-10 μm. In contrast, PVDF-HFP solution gives rise to a cellular microstructure following the same experimental procedures. We further elucidate the formation mechanism on the basis of the characterization by freeze fracture transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry characterizations. Furthermore, contact angle measurements of water on PVDF-HFP/graphene indicates that the hydrophobic nature of PVDF-HFP combined with the micro/nanoscale hierarchical texture creates a superhydrophobic surface. Such superhydrophobic microspheres may have potential applications as water-repellent catalyst-supporting materials.

Wettability modification of graphene oxide by removal of carboxyl functional groups using non-thermal effects of microwave

“…al., for instance; reported that acetone or molecular water attaching to the surface of graphene can change its wettability to superhydrophilic [20]. In addition, there are several reports that have tried to enhanced wettabilty of graphene based composites [21][22][23][24]. Although it is known that functional groups such as hydroxyl and carboxyl are hydrophilic however, due to the presence of various functional groups on the GO surface, the main hydrophilic functional group is not clear.…”

A nanocellular PVDF–graphite water-repellent composite coating

“…With addition of 1 wt% graphite powder, the melting temperature of dried PVDF composite increased slightly. 63 However, dry PVDF composite samples showed a widening peak compared to pure PVDF samples, and this is illustrated in the cooling curves.…”

Superhydrophobic carbon-based materials: a review of synthesis, structure, and applications

“…3, fluorinated polymers are commonly used as low surface energy materials; for example, polyvinylidene fluoride (PVDF) is used to produce superhydrophobic materials [134][135][136]. Zha et al [135] demonstrated a combined method of solvent exchanging and freeze-drying to fabricate PVDF porous materials that can effectively avoid the skin-layer formation of dried materials.…”

“…Several experimental and modeling studies have focused on exploiting micro-scale surface roughness to engineer superhydrophobic graphene. Several research groups have fabricated superhydrophobic graphene surfaces using an irregular stack of graphene oxides (GO) prepared by chemical oxidation of graphite, and pertinent results are shown in Table 2 [131][132][133][134][135][136][137][138][139][140][141][142][143][144]. blocks to create a superhydrophobic structure with an ordered pore structure of ~200 μm in dimension.…”

“…On the basis of the Cassie-Baxter model, such multilevel surface roughness is responsible for its superhydrophobicity. Zhang et al [136] demonstrated the fabrication of hybrid PVDF-hexafluoropropylene (HFP)/graphene composite microspheres through a spontaneous formation process. The addition of graphene to a PVDF-HFP/DMF solution has a strong influence on its gel structure in both the wet and dry states.…”