Separating oil–water mixtures is a common obstacle in many processes from wastewater treatment to biofuel manufacture to cleanup of oil spills. There is an urgent need for new, fast, and simple technologies for such separations. In this work, we describe a simple and practical route for creating superoleophilic electrospun membranes that are capable of selectively passing oil and organic compounds at very high rates in a gravity-driven system while retaining water. To prepare these membranes, we blended a new, highly fluorinated random copolymer (FCP), poly­(methyl methacrylate-random-perfluorodecyl methacrylate), P­(MMA-r-FDMA), with the commodity polymer poly­(vinylidene fluoride) (PVDF) and prepared electrospun membranes from their mixture. Membranes composed of nonwoven fibers with uniform and bead-free morphology were obtained upon electrospinning of PVDF blended with this FCP. The PMMA segments provided anchors to the PVDF matrix, resulting in significant enhancement in the mechanical properties with up to 7 times higher Young’s modulus for the blend membranes. Moreover, the self-organization of the long, pendant FDMA side groups within the PVDF matrix resulted in fluorine-rich, highly hydrophobic and superoleophilic surface. As a result, the FCP-containing membranes exhibited up to 17 times faster permeation of oil and organic solvent, compared with pure PVDF membrane in gravity-driven filtration experiments. Their performance was highly stable during a 70 min continuous gravity-driven filtration experiment for oil/water separation, reflecting their excellent fouling resistant properties. This easy-to-implement and cost-effective approach, combined with the high porosity and re-entrant structure created by the electrospinning, can create membranes with excellent mechanical properties and fouling resistance.

Nonwoven super‐hydrophobic fiber membranes have potential applications in oil–water separation and membrane distillation, but fouling negatively impacts both applications. Membranes were prepared from blends comprising poly(vinylidene fluoride) (PVDF) and random zwitterionic copolymers of poly(methyl methacrylate) (PMMA) with sulfobetaine methacrylate (SBMA) or with sulfobetaine‐2‐vinylpyridine (SB2VP). PVDF imparts mechanical strength to the membrane, while the copolymers enhance fouling resistance. Blend composition was varied by controlling the PVDF‐to‐copolymer ratio. Nonwoven fiber membranes were obtained by electrospinning solutions of PVDF and the copolymers in a mixed solvent of N,N‐dimethylacetamide and acetone. The PVDF crystal phases and crystallinities of the blends were studied using wide‐angle X‐ray diffraction and differential scanning calorimetry (DSC). PVDF crystallized preferentially into its polar β‐phase, though its degree of crystallinity was reduced with increased addition of the random copolymers. Thermogravimetry (TG) showed that the degradation temperatures varied systematically with blend composition. PVDF blends with either copolymer showed significant increase of fouling resistance. Membranes prepared from blends containing 10% P(MMA‐ran‐SB2VP) had the highest fouling resistance, with a fivefold decrease in protein adsorption on the surface, compared to homopolymer PVDF. They also exhibited higher pure water flux, and better oil removal in oil–water separation experiments. © 2018 Society of Chemical Industry

We report the structure and thermal properties of blends comprising poly(vinylidene fluoride) (PVDF) and a random fluorinated copolymer (FCP) of poly(methyl methacrylate)‐random‐1H,1H,2H,2H‐perfluorodecyl methacrylate, promising membrane materials for oil–water separation. The roles of processing method and copolymer content on structure and properties were studied for fibrous membranes and films with varying compositions. Bead‐free, nonwoven fibrous membranes were obtained by electrospinning. Fiber diameters ranged from 0.4 to 1.9 μm, and thinner fibers were obtained for PVDF content >80%. As copolymer content increased, degree of crystallinity and onset of degradation for each blend decreased. Processing conditions have a greater impact on the crystallographic phase of PVDF than copolymer content. Fibers have polar beta phase; solution‐cast films contain gamma and beta phase; and melt crystallized films form alpha phase. Kwei's model was used to model the glass transition temperatures of the blends. Addition of FCP increases hydrophobicity of the electrospun membranes. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 312–322

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Fast scanning calorimetry (FSC) is used to study crystallization of poly(vinylidene fluoride) (PVDF), and its blends with a random fluorinated copolymer (FCP) of poly(methyl methacrylate) and 1H,1H,2H,2H‐perfluorodecyl methacrylate (PMMA‐r‐PFDMA). By varying the residence time at isothermal melt crystallization temperatures TMC = 80–120°C, the amount of α‐ and β‐phase can be controlled, yielding partial or complete suppression of β‐phase for all blends studied. Nonisothermal crystallization kinetics are also studied by FSC and analyzed using the Mo model. Crystallization rates increase when FCP is present. PVDF crystallizes into β‐phase when cooled from the melt at rates faster than 3000 K/s giving PVDF crystal fractions of about 0.05–0.16. Only α‐phase occurs at cooling rates slower than 2000 K/s yielding larger PVDF crystal fractions of about 0.30–0.43. Cooling rates between those limits result in mixed α‐ and β‐phase. The rigid amorphous fraction (RAF) of PVDF varies with α and β crystal fraction in PVDF/FCP blends. RAF of α‐phase PVDF ranges from 0.21 to 0.28 whereas RAF of β‐phase PVDF spans a wider range, reaching values from 0.42 to 0.46.