Fluorocarbon Chains Research Articles

Molecular Dynamics Simulation for Surface and Transport Properties of Fluorinated Silica Nanoparticles in Water or Decane: Application to Gas Recovery Enhancement

Determination of surface and transport properties of nanoparticles (NPs) is essential for a variety of applications in enhanced oil and gas recoveries. In this paper, the impact of the surface chemistry of silica NPs on their hydro- and oleo-phobic properties as well as their transport properties are investigated in water or decane using molecular dynamics simulation. Trifluoromethyl or pentafluoroethyl groups as water and oil repellents are placed on the NPs. It is found that the density and residence time of liquid molecules around the NPs are modulated considerably with the existence of the functional groups on the NPs’ surfaces. Also, much larger density fluctuations for liquids close to the surface of the NPs are observed when the number of the groups on the NPs increases, indicating increased hydrophobicity. In addition, the diffusion coefficient of the NPs in either water or decane increases with increasing the number or length of the fluorocarbon chains, demonstrating non-Brownian behavior for the NPs. The surface chemistry imparts a considerable contribution on the diffusion coefficient of the NPs. Finally, potential of mean force calculations are undertaken. It is observed that the free energy of adsorption of the NPs on a mineral surface is more favorable than that of the aggregation of the NPs, which suggests the NPs adsorb preferably on the mineral surface.

Oleophobic/Adhesive Janus Self-Standing Films Modified with Bifurcated Short Fluorocarbon Chains as Transparent Oil Stain-Free Coating with Attachability

Oil stains negatively affect the performances of our belongings and industrial equipment. However, conventional oleophobic coatings contain complex nanostructures or long fluoroalkyl chains, which are environmentally unsafe and limit their applications. In addition, the integration of film transparency, flexibility, and oleophobicity represent extremely challenging tasks. Herein, we report self-standing oleophobic/adhesive Janus membranes with flexibility and transparency, which were composed of environmentally low impact materials: poly(vinyl alcohol) (PVA)/SiO2 nanoparticle composites modified with bifurcated short fluorocarbon chains via the sol–gel method. The optimized coating performed the oleophobicity (oleic acid sliding angle = 27.9°) and reduced more than 50% of oil adhesion on glass substrate. It also maintained its transparency (93.13% at wavelength of 550 nm) after the exposure to oil mist. Moreover, the coatings were able to attach to various substrates to provide them an oleophobicity. Our results demonstrate the important role to develop oleophobic coating materials with low environmental impact.

2,5-Bis[(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)sulfanyl]-1,3,4-thiadiazole

The title compound, C18H8F26N2S3, was obtained by doubleS-perfluorohexylethylation of dipotassium 1,3,4-thiadiazole-2,5-dithiolate in methanol. The molecule exhibits twofold rotational symmetry, with the S atom lying on the rotation axis. The fluorocarbon chains adopt helical conformations and the F atoms of the two terminal C atoms are disordered over two sets of sites. No directional intermolecular interactions occur in the crystal.

Structural characterization of new fluorinated mesogens obtained through halogen-bond driven self-assembly

We describe the synthesis and characterization of new trimeric complexes obtained upon halogen-bond driven self-assembly of 1,4-diiodotetrafluorobenzene or α,ω– diiodoperfluoroalkanes, acting as XB-donors, with an alkoxystilbazole derivative functionalized with a methacrylate terminal group, acting as XB-acceptor. Despite the fact that the starting materials are not mesomorphic in nature, the obtained halogen-bonded complexes exhibit monotropic LC behaviour with smectic A phases possibly resulting from segregation between fluorocarbon and hydrocarbon chains. The obtained supramolecular mesogens possess reactive groups suitable for incorporation into liquid crystalline elastomeric actuators.

Serum-resistant, reactive oxygen species (ROS)-potentiated gene delivery in cancer cells mediated by fluorinated, diselenide-crosslinked polyplexes.

The transfection performance of polycations is often hampered by various systemic barriers that pose conflicting requirements for material design. Herein, we developed fluorinated, ROS-cleavable polyethylenimine (PEI) for effective and serum-resistant gene delivery to cancer cells, by harmonizing the inconsistency between DNA condensation and release, and the inconsistency between cellular internalization and serum stability. Low-molecular weight (MW) PEI was cross-linked with a diselenide-containing linker and further modified with fluorocarbon chains. The obtained high-MW DSe-PEI-F has potent DNA condensation as well as intracellular DNA delivery capabilities, while in the cytoplasm of cancer cells, it can rapidly degrade into low-MW segments upon ROS treatment to promote DNA release and reduce the material toxicity. As such, DSe-PEI-F showed high transfection efficiencies in cancer cells in the presence of serum, outperforming the commercial reagent PEI 25k by several orders of magnitude. This study thus provides an effective approach to overcome various barriers against non-viral gene delivery, which contributes to the development of a new class of gene vectors with high efficiency and low toxicity.

Synthesis of hydrophobic fluorinated polyurethanes and their properties of resistance to cavitation and wear

Abstract Hydrophobic fluorinated polyurethanes (FPU) without hydrophilic CH 2 OH groups were prepared by introducing fluorine with the method of perfluoroalkyl ethanols (TEOH-10) for modification of diphenyl-methane-diisocyanates (MDI) and regulating the dosage and time of the MDI added. The experiment of water resistance indicates that the hydrophobicity of the FPU are very strong, owing to the low surface energy of fluorocarbon chains (-CF 2 CF 3 ) migrating to the surface of material and forming the organic fluorine membrane which was equivalent to the hydrophobic effect of the lotus leaf. Especially when the molar dosage of TEOH-10 was 0.3–0.5 theoretical quantity of MDI, the water absorption of FPU is only between 0.0146% and 0.0182%, and the high cohesive pressure of FPU maintained at 10.31MPa–10.79 MPa after 3200 h’ water soaking. The erosion wear experiment showes that the anti-erosion performance of FPU continuously improved with the increasing of fluorine content, however, the cohesive pressure of FPU continuously reduced with the increasing of fluorine content. Comprehensive consideration of water conservancy and hydropower engineering application requirements of underwater protective coating, when the molar ratio of TEOH-10 versus MDI was about 0.5, the cavitation erosion amount of FPU reduced from 2.3756 × 10 −3 kg to 0.9334 × 10 −3 kg, and the cohesive pressure of FPU stayed over 10 MPa, which can be used as protective coating of flow components under water.

Separation of organic liquid mixture by flexible nanofibrous membranes with precisely tunable wettability

Separation of liquid mixtures, especially organic liquid mixtures, is widely used in industrial processes but still faces challenges with respect to separation in a high-efficiency, low-energy mode. In this work, we report a flexible wettability-tunable nanofibrous membrane composed of a high-performance fluoro-polymer as the matrix and fluorosilane as a surface energy regulator that can be successfully applied in immiscible organic liquid mixture separation. The separation is achieved by tuning the surface energy of a membrane to a value between the surface tensions of two organic liquids. Moreover, for use in different mixed liquid systems, we programmatically designed nanofibrous membranes with the proper surface energy that could intercept the relatively high surface tension liquid and allow the low surface tension liquid to pass through. These membranes are expected to become a competitive candidate for complex organic chemical product separation, resource recycling, and environmental protection. Polymer nanofibre membranes with tunable wetting properties can match the surface tension of complex liquids and separate them. Purifying organic liquids with similar physical properties often requires energy-intensive methods. However, a membrane developed by Yong Zhao from Beihang University in China and colleagues offers high-throughput separation, thanks to incorporate of ‘dopants’ made from long silicon fluorocarbon chains, which repel both water and oil, into electrospun nanofibres made from poly(vinylidene fluoride-co-hexafluoropropylene enabled the team to selectively adjust membrane wetting to match organic liquid targets. With organic liquids having slightly different surface tensions, such as propylene glycol and benzene solutions, the membranes intercepted the high-surface tension liquid while the other passed through spontaneously. The flexible membrane offers improved mechanical properties over conventional ceramic membranes and is promising for cleaning oil spills and treating other environmental problems. Organic liquid separation is currently an important but troublesome issue, which closely related to resource recycling and environmental protection. Here we reported a wettability-tunable nanofibrous membrane that can be used for efficient separation of wide ranges of immiscible organic liquid mixtures.

Self-Assembly of Polyoxovanadate-Containing Fluorosurfactants.

Two novel polyoxovanadate (POV)-containing fluorosurfactants, each with two hydrophobic fluorinated "tails" and one nanosized, hydrophilic, rigid POV "head group", are synthesized for the first time. They self-assemble into spherical, bilayer vesicles in acetonitrile/water mixed solvents, as evidenced by systemic studies using laser light scattering (LLS) and electron microscopy techniques. The vesicle sizes demonstrate dynamic change over different solvent compositions mainly as a result of the solvent swelling of the fluorocarbon chains, although the charge number on the POVs changes over the solvent polarity as well.

Development of original metabolically stable apelin-17 analogs with diuretic and cardiovascular effects.

Apelin, a (neuro)vasoactive peptide, plays a prominent role in controlling cardiovascular functions and water balance. Because the in vivo apelin half-life is in the minute range, we aimed to identify metabolically stable apelin-17 (K17F) analogs. We generated P92 by classic chemical substitutions and LIT01-196 by original addition of a fluorocarbon chain to the N terminus of K17F. Both analogs were much more stable in plasma (half-life >24 h for LIT01-196) than K17F (4.6 min). Analogs displayed a subnanomolar affinity for the apelin receptor and behaved as full agonists with regard to cAMP production, ERK phosphorylation, and apelin receptor internalization. Ex vivo, these compounds induced vasorelaxation of rat aortas and glomerular arterioles, respectively, precontracted with norepinephrine and angiotensin II, and increased cardiac contractility. In vivo, after intracerebroventricular administration in water-deprived mice, P92 and LIT01-196 were 6 and 160 times, respectively, more efficient at inhibiting systemic vasopressin release than K17F. Administered intravenously (nmol/kg range) in normotensive rats, these analogs potently increased urine output and induced a profound and sustained decrease in arterial blood pressure. In summary, these new compounds, which favor diuresis and improve cardiac contractility while reducing vascular resistances, represent promising candidates for the treatment of heart failure and water retention/hyponatremic disorders.-Gerbier, R., Alvear-Perez, R., Margathe, J.-F., Flahault, A., Couvineau, P., Gao, J., De Mota, N., Dabire, H., Li, B., Ceraudo, E., Hus-Citharel, A., Esteoulle, L., Bisoo, C., Hibert, M., Berdeaux, A., Iturrioz, X., Bonnet, D., Llorens-Cortes, C. Development of original metabolically stable apelin-17 analogs with diuretic and cardiovascular effects.

Highly Stable Fluorinated Nanocarriers with iRGD for Overcoming the Stability Dilemma and Enhancing Tumor Penetration in an Orthotopic Breast Cancer.

The stability dilemma and limited tumor penetration of nanocarriers in cancer chemotherapy remain two predominant challenges for their successful clinical translation. Herein, the pH-sensitive fluorocarbon-functionalized nanocarriers (SFNs) with a tumor-homing and penetrating peptide iRGD are reported to overcome the stability dilemma and enhance tumor accumulation and penetration in an orthotopic breast cancer. The highly stable SFNs with a low critical association concentration provide a safe and spacious harbor for hydrophobic drugs. Furthermore, the stimulus-responsive evaluation and in vitro drug release study show that the SFNs can balance intracellular dissociation for drug release and extracellular stability in the blood circulation. Additionally, the tumor penetration capacity has been dramatically enhanced in 3D multicellular spheroids, effectively affecting cells far from the periphery. This can be ascribed to the coadministration of iRGD having tumor-penetrating ability and fluorocarbon chains having good cell membrane permeability. The combination of SFNs and iRGD is a viable approach to assist drugs' effective accumulation in primary and metastasized tumor sites, significantly inhibiting the breast tumor growth and curbing lung and liver metastases in an orthotopic-tumor-bearing mouse model. Taken together, this pH-sensitive fluorinated nanosystem having excellent stability and tumor accumulation and penetration properties paves the way to combat cancer.

Characterization of plasma deposited poly(heptadecafluoro-1-decene)

Abstract Fluorocarbon coatings were deposited by plasma polymerization of 1H,1H,2H-perfluoro-1-decene (HDFD). Chemical and morphological characterization of coatings obtained from different process parameters was performed by means of Attenuated Total Reflectance Fourier Transform Infrared (FTIR/ATR) spectroscopy, Energy Dispersive X-Ray analysis (EDX) and Atomic Force Microscopy (AFM). Hydro- and oleo-repellency were evaluated by contact angle measurements with different liquids. Optical properties were investigated by acquiring the transmittance spectra in the region 300–900 nm. Finally, evaluation of the mechanical properties was performed by means AFM nanoindentation. By increasing the Yasuda factor (the energy consumed per mass of monomer), coatings with lower retention of fluorocarbon chains were obtained. The F/C ratio, measured by means of EDX analysis, decreased from 0.85 for coatings deposited at 10 W to 0.69 for coatings deposited at 100 W. As a consequence of the lower retention of fluorocarbon chains, coatings deposited at high Yasuda factors displayed lower hydro- and oleo-repellency. In addition, these coatings contains large amount of unsaturated groups (CF CF, CF C CF, …), as assessed by ATR analysis. This led to a lower transparency, due to radiation absorption in the visible region. On the other hand, the mechanical properties (and hence the durability) of the coatings increased with the energy consumed per monomer molecule.

New Class of Amphiphiles Designed for Use in Water-in-Supercritical CO2 Microemulsions.

Water-in-supercritical CO2 microemulsions formed using the hybrid F-H surfactant sodium 1-oxo-1-[4-(perfluorohexyl)phenyl]hexane-2-sulfonate, FC6-HC4, have recently been shown to have the highest water-solubilizing power ever reported. FC6-HC4 demonstrated the ability to outperform not only other surfactants but also other FCm-HCn analogues containing different fluorocarbon and hydrocarbon chain lengths (Sagisaka, M. et al. Langmuir 2015, 31, 7479-7487). With the aim of clarifying the key structural features of this surfactant, this study examined the phase behavior and water/supercritical CO2 aggregate formation of 1-oxo-1-[4-(perfluorohexyl)phenyl]hexane (Nohead FC6-HC4), which is an FC6-HC4 analogue but now, interestingly, without the sulfonate headgroup. Surprisingly, Nohead FC6-HC4, which would not normally be identified as a classic surfactant, yielded transparent single-phase W/CO2 microemulsions with polar cores able to solubilize a water-soluble dye, even at pressures and temperatures so low as to approach the critical point of CO2 (e.g., ∼100 bar at 35 °C). High-pressure small-angle scattering (SANS) measurements revealed the transparent phases to consist of ellipsoidal nanodroplets of water. The morphology of these droplets was shown to be dependent on the pressure, Nohead FC6-HC4 concentration, and water-to-surfactant molar ratio. Despite having almost the same structure as Nohead FC6-HC4, analogues containing both shorter and longer hydrocarbons were unable to form W/CO2 microemulsion droplets. This shows the importance of the role of the hydrocarbon chain in the stabilization of W/CO2 microemulsions. A detailed examination of the mechanism of Nohead FC6-HC4 adsorption onto the water surface suggests that the hexanoyl group protrudes into the aqueous core, allowing for association between the carbonyl group and water.

An Investigation on the Friction and Wear Properties of Perfluorooctane Sulfonate Ionic Liquids

The study aims to explore the physicochemical and tribological properties of perfluorooctane sulfonate ionic liquids (PSILs) C8F17SO3N4444 and C8F17SO3P4444. The results showed that C8F17SO3P4444 exhibited excellent friction-reducing and anti-wear properties at both room and high temperatures, and C8F17SO3N4444 presented excellent tribological properties at high temperature when they were used as lubricants for steel/steel, steel/copper, and steel/aluminum friction pairs. As compared with traditional fluorine-containing ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide (L-F104), increasing the fluorocarbon chain length of the anion is proven to be an effective way to improve the performance of the PSILs in terms of hydrophobicity, corrosion resistance, and tolerance to extreme pressure, thereby making them more suitable to be used as lubricants under harsh conditions. The X-ray photoelectron spectroscopy analysis indicated that physical adsorption and tribochemical reactions occurred and generated protective films on the sliding surface during the rubbing process, which reduced the friction and elevated the anti-wear efficiency of the PSILs.

Chemical Functionalisation of Cotton Fabric to Impart Multifunctional Properties

A cotton fabric was functionalised using the nanoparticle vapor deposition (NVD) and molecular vapor deposition (MVD) techniques to impart super hydrophobic/oleophobic properties. The NVD method was used to deposit a layer of Al2O3 nanoparticles onto the fabric surface. MVD led to the deposition of a functional layer of (tridecafl uoro-1,1,2,2,-tetrahydrooctyl)trichlorosilane (FOTS). The nanoparticles deposition increased the surface roughness, leading to higher contact angles when compared with the surfaces functionalised only with FOTS. FTIR spectra showed the presence of peaks corresponding to fluorocarbon chains and Al2O3on functionalised samples. Surface free energies of the samples were calculated. Low hysteresis and dynamic contact angles higher than 150° were obtained for water and organic liquids. Tetrabutyl orthotitanate (Ti(OC4H9)4) was used to functionalise fabrics to impart self-cleaning and UV protection properties. Furthermore, the functionalisation with monochlorotriazyl-β-cyclodextrin molecules introduced cavities on the fabric surface, which were used to perform the inclusion of antimicrobial agents.

Surface Enrichment of Fluorocarbon End-Capped Polymers with Different Fluorocarbon Lengths.

This study investigated the surface structure of fluorocarbon end-capped l-poly(lactide)s (F-PLLA) with different fluorocarbon lengths by electron spectroscopy for chemical analysis (ESCA). Fluorocarbon chains of three lengths (F(CF2)n(CH2)2, where n = 6, 8, and 10) have been synthesized as the terminal group to PLLA. Angular dependent ESCA revealed that the fluorocarbon groups are segregated at the surface. Further, the results show the surface coverage of fluorocarbon groups rapidly increases with increasing the length of fluorocarbon end groups (synergy effect). The surface composition of F-PLLAs can be controlled by changing the length of fluorocarbon.

Fluidizing and Solidifying Effects of Perfluorooctylated Fatty Alcohols on Pulmonary Surfactant Monolayers.

Pulmonary surfactant (PS) preparations based mainly on bovine or porcine extracts are commonly administered to patients with neonatal respiratory distress syndrome (NRDS) for therapy. The preparations are sufficiently effective to treat NRDS; however, they are associated with a risk of infection and involve costly purification procedures to achieve batch-to-batch reproducibility. Therefore, we investigated the mechanism and interfacial behavior of synthetic PS preparations containing a mimicking peptide (KLLKLLLKLWLKLLKLLL, Hel 13-5). In particular, a hybrid PS formulation with fluorinated amphiphiles is reported from the perspective of surface chemistry. Fluorinated amphiphiles are characterized by exceptional chemical and biological inertness, high oxygen-dissolving capacity, low surface tension, excellent spreading ability, and high fluidity. These properties are superior to those for the corresponding hydrocarbon analogs. Indeed, a small amount of fluorinated long-chain alcohols enhances the effectiveness of the model PS preparation for in vitro pulmonary functions. Moreover, the mode of the improved efficacy differs depending on the hydrophobic chain length in the alcohols. For alcohols with a short fluorocarbon (FC) chain, the monolayer phase of the model PS preparation remains disordered (fluidization). However, the addition of alcohols containing a long FC chain reduces the disordered/ordered phase transition pressure and the growth of ordered domains of the monolayer (condensation). Furthermore, repeated compression-expansion isotherms of the monolayers, which can simulate respiration in the lung, suggest irreversible elimination of the short-FC alcohol into the subphase and enhancement of the squeeze-out phenomenon of certain PS components by solid-like monolayer formation induced by the long-FC alcohol. We demonstrated that fluorinated amphiphiles may be used as additives for synthetic or commercial PS preparations for RDS treatment.

The self-assembly structure and the CO2-philicity of a hybrid surfactant in supercritical CO2: effects of hydrocarbon chain length.

Hybrid surfactants containing both fluorocarbon (FC) and hydrocarbon (HC) chains, as effective CO2-philic surfactants, could improve the solubility of polar substances in supercritical CO2. Varying the length of the HC of hybrid surfactants is an effective way to improve the CO2-philicity. In this paper, we have investigated the effects of the HC length on the self-assembly process and the CO2-philicity of hybrid surfactants (F7Hn, n = 1, 4, 7 and 10) in water/CO2 mixtures using molecular dynamics simulations. It is found that the self-assembly time of F7Hn exhibits a maximum when the length of the HC is equal to that of the FC (F7H7). In this case, the investigation of H-bonds between the water core and CO2 phase shows that F7H7 has the strongest CO2-philicity because it has the best ability to separate water and CO2. To explain the origin of the differences in separation ability, the analysis of the structures of the reverse micelles shows that there are two competing mechanisms with a shortening HC. Firstly, the volume of F7Hn is reduced, which thus decreases the separation ability. Moreover, this also leads to the curved conformation of the FC. As a result, the separation ability is enhanced. These two mechanisms are balanced in F7H7, which has the best ability to separate water and CO2. Our simulation results demonstrate that the increased volume and the curved conformation of the hybrid surfactant tail could enhance the CO2-philicity in F7Hn surfactants. It is expected that this work will provide valuable information for the design of CO2-philic surfactants.

Synthesis and Solution Properties of Adamantane Containing Quaternary Ammonium Salt-type Cationic Surfactants: Hydrocarbon–based, Fluorocarbonbased and Bola–type

Quaternary ammonium salt-type cationic surfactants with an adamantyl group (hydrocarbon-type; CnAdAB, fluorocarbon-type; CmFC3AdAB, bola-type; Ad-s-Ad, where n, m and s represent hydrocarbon chain lengths of 8-16, fluorocarbon chain lengths of 4-8, and spacer chain length of 10-12) were synthesized via quaternization of N, N-dimethylaminoadamantane and n-alkyl bromide or 1, n-dibromoalkane. Conductivity and surface tension were measured to characterize the solution properties of the synthesized adamantyl group-containing cationic surfactants. In addition, the effects of hydrocarbon and fluorocarbon chain lengths and spacer chain length between headgroups on the measured properties were evaluated by comparison with those of conventional cationic surfactants. The critical micelle concentration (CMC) of CnAdAB and Ad-s-Ad was 2/5 of that for the corresponding conventional surfactants CnTAB and bola-type surfactants with similar number of carbons in the alkyl or alkylene chain; this was because of the increased hydrophobicity due to the adamantyl group. A linear relationship between the logarithm of CMC and the hydrocarbon chain length for CnAdAB was observed, as well as for CnTAB. The slope of the linear correlation for both surfactants was almost the same, indicating that the adamantyl group does not affect the CMC with variations in the hydrocarbon chain length. Similar to conventional surfactants CnTAB, the hydrocarbon-type CnAdAB is highly efficient in reducing the surface tension of water, despite the large occupied area per molecule resulting from the relatively bulky structure of the adamantane skeleton. On the other hand, the bola-type Ad-s-Ad resulted in increased surface tension compared to CnAdAB, indicating that the curved chain between adamantyl groups leads to poor adsorption and orientation at the air-water interface.

Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

Self-assembled monolayers (SAMs) were prepared on gold substrates from an unsymmetrical partially fluorinated spiroalkanedithiol adsorbate with the specific structure of [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT) and compared to SAMs formed from the semifluorinated monothiol F8H10SH [CF3(CF2)7(CH2)10SH] of analogous chain length and n-octadecanethiol. The adsorbate with two alkyl chains, one terminally fluorinated and the other nonfluorinated, was designed to form monolayers in which the bulky helical fluorocarbon segments assemble on top of an underlying layer of well-packed trans-extended alkyl chains. Different combinations of deposition solvents and temperatures were used to produce the bidentate SAMs. Characterization of the resulting monolayers revealed that SAMs formed in DMF at room temperature allow complete binding of the sulfur headgroups to the surface and exhibit higher conformational order than those produced using alternative solvent/temperature combinations. The reduced film thicknesses and enhanced wettability of the SADT SAMs, as compared to the SAMs generated from F8H10SH, suggest loose packing and an increase in the tilt of the terminal fluorocarbon chain segments. Nevertheless, the density of the underlying hydrocarbon chains of the SADT SAMs was higher than that of the F8H10SH SAMs, owing to the double-chained structure of the new adsorbate. The conformational orders of the SAM systems were observed to decrease as follows: C18SH > F8H10SH > SADT. However, the SAMs formed from this new double-chained bidentate adsorbate in DMF expose a fluorinated interface with a relatively low surface roughness, as determined by contact-angle hysteresis.

Sorption of perfluorooctanoic acid, perfluorooctane sulfonate and perfluoroheptanoic acid on granular activated carbon.

The sorption of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluoroheptanoic acid (PFHpA) on granular activated carbon (GAC) was characterized and compared to explore the underlying mechanisms. Sorption of the three perfluoroalkyl acids (PFAAs) on GAC appeared to be a rapid intra-particle diffusion process, which were well represented by the pseudo-second-order rate model with the sorption rate following the order PFOS > PFOA > PFHpA. Sorption isotherm data were well fitted by the Freundlich model with the sorption capacity (Kf) of PFOS, PFOA and PFHpA being 4.45, 2.42 and 1.66 respectively. This suggests that the hydrophilic head group on PFAAs, i.e. sulfonate vs carboxylic, has a strong influence on their sorption. Comparison between PFOA and PFHpA revealed that hydrophobicity could also play a role in the sorption of PFAAs on GAC when the fluorocarbon chain length is different. Analyses using Attenuated Total Reflection (ATR)-Fourier Transform Infrared (FTIR) spectroscopy suggested possible formation of a negative charge-assisted H-bond between PFAAs and the functionalities on GAC surfaces, including non-aromatic ketones, sulfides, and halogenated hydrocarbons.