Abstract  A new family of porous fluorinated membranes was developed from perfluoropolyethers (PFPEs). The PFFE-dimethacrylate (3) was dispersed in isopropanol to form a clear homogeneous solution, which after UV curing in polypropylene molds formed a porous polymer disk. A series of 10 polymers was prepared with ratios of isopropanol to PFPE ranging from 1.3:1 to 0.2:1. The water content of the membranes after hydration varied from 56 to 7% (w/w) and was directly proportional to the percentage of isopropanol used in the polymerization. However, the tensile elastic modulus, which ranged from 0.17 to 15 MPa, was inversely proportional to the water content. The high water content membranes 152 and 46% (w/w)] had a similar permeability to glucose, inulin, and albumin, while the membranes with lower water contents of 37 and 25% displayed progressively lower permeability. (C) 2001 John Wiley & Sons, Inc.

Abstract  Supplemental materials

Abstract  In 2007 the Minnesota State Legislature passed Minnesota Statute 144.995 - 144.998, which established the Environmental Health Tracking and Biomonitoring (EHTB) program and directed the Minnesota Department of Health (MDH) to design and implement four pilot biomonitoring projects. The primary purpose of each of the pilot projects is to measure the range and distribution of a selected chemical or chemicals, in the body, in a community identified as likely to be exposed. Exposure is measured through the collection of a biological sample, such as blood or urine, from voluntary participants from the community. Another purpose of the pilot projects is to build biomonitoring capacity in the,sjare and-to .develop recommendations for the Legislature for the creation of an ongoing biomonitoring program in Minnesota. This biomonitoring pilot project, known as the East Metro PFC Biomonitoring Pilot Project, was designed to measure the range and distribution of 7 types of perfluorinated chemicals (PFCs) in 100 individuals from each of two separate communities. Contamination of drinking water supplies with PFCs in the east metro was discovered in the summer of 2004. MPCA and MDH collected water samples from private well owners as well as the Oakdale Municipal supply to assess and define the extent of the contamination. Routine monitoring was established by MDH and MPCA and actions to stop drinking water exposure were taken, including the provision ofbottled water, granular activated carbon (GAC) home filters, access to municipal water, and a water treatment plant that utilizes large GAC filters to remove PFCs for the Oakdale Municipal Water Supply'. With the implementation of these filtration practices, drinking water exposure in the community has been reduced to below established health-based values, and the plan for remediation of the contaminated waste facilities are currently underway which may further reduce the PFC exposure through drinking water.

Abstract  Through cooperation with six American Red Cross blood banks, 645 serum samples . from adult donors (ages 20-69, equally represented of both sexes) were obtained for fluorochemical analyses. Blood bank locations were Los Angeles (CA), Portland (OR), Minneapolis-St. Paul (MN), Charlotte (NC), Hagerstown (MD) and Boston (MA). Samples were void of personal identifiers. Age, gender and location were the only known demographic factors. Sera samples were extracted and quantitatively analyzed for seven fluorochemicals using high-pressure liquid chromatography/electrospray tandem mass spectrometry and evaluated versus an extracted curve from a human plasma matrix. The seven fluorochemicals were perfluorooctanesulfonate (PFOS, CsF11SO3); N-ethyl pertluorooctanesulfonamidoacetate (PFOSAA, C8F 17SO2N (CH2CH3)CH2COO-); Nmethyl perfluorooctanesulfonamidoacetate (M570, CsF11SO2N(CH3)CH2COO'); perfluorooctanesulfonamidoacetate (M556, CsF 11SO2N( CH)CH2COO-); pertluorooctanesulfonylamide (PFOSA, C8F17SO2NH2); perfluorooctanoate (PFOA, C7F13COO); and perfluorohexanesulfonate (PFHS C6F13SO3). Overall, the geometric mean measured concentration of PFOS was 34.9 ppb (95% CI 33.3-36.5). The measured PFOS concentration ranged from less than the lower limit of quantitation (LLOQ) of 4.1 ppb to 1656.0 ppb. The geometric mean for PFOS was significantly higher among males (37.8 ppb; 95% CI 35.5-40.3) than females (31.3 ppb; 95% CI 30.0-34.3). No significant difference was observed with age. Charlotte (NC) had the highest geometric mean serum PFOS concentration (51.5 ppb) and Boston (MA) the lowest (29.5 ppb). Bootstrap analyses were used to calculate a 95% tolerance limit for PFOS of 88.5 ppb with an upper 95% confidence limit of 100.0 ppb. Additional geometric mean and tolerance limit data are reported for PFOA, PFHS, PFOSAA and M570. The geometric mean and 95% tolerance limits of these fluorochemicals were, on average, an order of magnitude (or more) lower than PFOS. PFOS and PFOA were highly correlated (r = .63). PFOS had lower correlations with PFOSAA (r = .42), PFHS (r = .38) and M570 (r = .20). The number of samples with measured PFOSA and M556 concentrations below the LLOQ prohibited meaningful statistical analyses for these compounds. The findings from this analysis of serum PFOS concentrations are consistent with those previously reported. The human data, to date, suggests the approximate average serum concentration in non-occupational adult populations may be 30 to 40 ppb with 95% of a population's serum PFOS concentrations below 100 ppb. Since serum PFOS concentrations likely reflect cumulative human expo-sure, this information will be usefui for risk characterization.

Abstract  The data provided in the presentation focus on plasma C4- C12 perfluorocarboxylate levels in samples collected in 2006 from donors in six different US locations. Comparisons are made to a similar set of data from samples collected in 2000. Declines were previously noted from 2000 - 2006 for perfluorooctanesulfonate (PFOS) and perfluoroooctanoate (PFOA) (see Olsen et al ES&T 2008; 42:4989-4995). In the presentation submitted herein, plasma concentrations for perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluoroundecanoate (PFUnDA), appeared to have increased. Strong correlations were also observed between higher chain lengths and weak correlations were observed between higher and lower chain lengths. Perfluorobutyrate (PFBA) was also measured and appeared to have declined between 2000 and 2006.

Abstract  A force field for perfluoropolyethers (PFPEs) based on the general optimized potentials for liquid simulations all-atom (OPLS-AA) force field has been derived in conjunction with experiments and ab initio quantum mechanical calculations. Vapor pressures and densities of two liquid PFPEs, perfluorodiglyme (CF3-O-(CF2-CF2-O)2-CF3) and perfluorotriglyme (CF3-O-(CF2-CF2-O)3-CF3), have been measured experimentally to validate the force field and increase our understanding of the physical properties of PFPEs. Force field parameters build upon those for related molecules (e.g., ethers and perfluoroalkanes) in the OPLS-AA force field, with new parameters introduced for interactions specific to PFPEs. Molecular dynamics simulations using the new force field demonstrate excellent agreement with ab initio calculations at the RHF/6-31G* level for gas-phase torsional energies (<0.5 kcal mol(-1) error) and molecular structures for several PFPEs, and also accurately reproduce experimentally determined densities (<0.02 g cm(-3) error) and enthalpies of vaporization derived from experimental vapor pressures (<0.3 kcal mol(-1)). Additional comparisons between experiment and simulation show that polyethers demonstrate a significant decrease in enthalpy of vaporization upon fluorination unlike related molecules (e.g., alkanes and alcohols). Simulation suggests this phenomenon is a result of reduced cohesion in liquid PFPEs due to a reduction in localized associations between backbone oxygen atoms and neighboring molecules.

Abstract  A simple method for constructing versatile ordered biotin/avidin arrays on UV-curable perfluoropolyethers (PFPEs) is presented. The goal is the realization of a versatile platform where any biotinylated biological ligands can be further linked to the underlying biotin/avidin array. To this end, microcontact arrayer and microcontact printing technologies were developed for photobiotin direct printing on PFPEs. As attested by fluorescence images, we demonstrate that this photoactive form of biotin is capable of grafting onto PFPEs surfaces during irradiation. Bioaffinity conjugation of the biotin/avidin system was subsequently exploited for further self-assembly avidin family proteins onto photobiotin arrays. The excellent fouling release PFPEs surface properties enable performing avidin assembly step simply by arrays incubation without PFPEs surface passivation or chemical modification to avoid unspecific biomolecule adsorption. Finally, as a proof of principle biotinylated heparin was successfully grafted onto photobiotin/avidin arrays.

Abstract  Two classes of novel lubricants, perfluoropolyethers (PFPE) and ionic liquids (ILs), were deposited on metal film magnetic tapes. The adhesive force and coefficient of friction of lubricated and unlubricated tapes were investigated at the nanoscale with an atomic force microscope (AFM) as a function of various humidity and temperature conditions. Microscale tests with a ball-on-flat tribometer were also performed in order to study the length-scale effects on friction. Wear at ultralow loads was simulated and the lubricant removal mechanism was investigated by monitoring the friction force, surface potential and contact resistance with the AFM. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) experiments were conducted to determine the chemical species that affect intermolecular bonding and as an aid in interpreting how the lubricant film tribological properties vary with the environmental conditions. Z-TETRAOL, one of the PFPEs, was found to exhibit the lowest adhesion and friction among the lubricant films studied. The ionic liquid 1,1'-(pentane-1,5-diyl)bis(3-hydroxyethyl-1H-imidazolium-1-yl) di[bis(trifluoromethanesulfonyl)imide)] exhibited comparable nanotribological properties with the PFPEs. This is attributed to the presence of hydroxyl groups at its chain ends, which can hydrogen bond with the surface similar to PFPEs.

Abstract  Amphiphilic networks of perfluoropolyethers (PFPE) and poly(ethylene glycol) (PEG) have been achieved to yield optically transparent, mechanically robust films over a wide range of compositions. Telechelic diols of these oligomers were transformed to a photocurable dimethacryloxy form (DMA) and free radically cured at various composition weight ratios to yield free-standing films. Clear and colorless amphiphilic networks could be achieved when low molar mass versions of both the PFPE-DMA (1 kg/mol) and the PEG-DMA (550 g/mol) were used. The bulk morphologies of the samples were extensively characterized by a variety of techniques including ultraviolet-visible spectroscopy, differential scanning calorimetry, dynamic mechanic thermal analysis, small-angle X-ray scattering, atomic force microscopy, X-ray photoelectron spectroscopy, and optical microscopy, which strongly suggest that nanoscopic to macroscopic phase-separated materials could be achieved. By incorporating a threshold amount of PFPEs into PEG-based hydrogel networks, water swelling could be significantly reduced, which may offer a new strategy for a number of medical device applications. Along these lines, strong inhibition of nonspecific protein adsorption could be achieved with these amphiphilic network materials compared with an oligo(ethylene glycol)-based self-assembled monolayer coated surface.

Abstract  The vacuum residue fraction of heavy crudes contributes to the viscosity of these oils. Specific microbial cleavage of C-S bonds in alkylsulfide bridges that form linkages in this fraction may result in dramatic viscosity reduction. To date, no bacterial strains have been shown conclusively to cleave C-S bonds within alkyl chains. Screening for microbes that can perform this activity was greatly facilitated by the use of a newly synthesized compound, bis-(3-pentafluorophenylpropyl)-sulfide (PFPS), as a novel sulfur source. The terminal pentafluorinated aromatic rings of PFPS preclude growth of aromatic ring-degrading bacteria but allow for selective enrichment of strains capable of cleaving C-S bonds. A unique bacterial strain, Rhodococcus sp. strain JVH1, that used PFPS as a sole sulfur source was isolated from an oil-contaminated environment. Gas chromatography-mass spectrometry analysis revealed that JVH1 oxidized PFPS to a sulfoxide and then a sulfone prior to cleaving the C-S bond to form an alcohol and, presumably, a sulfinate from which sulfur could be extracted for growth. Four known dibenzothiophene-desulfurizing strains, including Rhodococcus sp. strain IGTS8, were all unable to cleave the C-S bond in PFPS but could oxidize PFPS to the sulfone via the sulfoxide. Conversely, JVH1 was unable to oxidize dibenzothiophene but was able to use a variety of alkyl sulfides, in addition to PFPS, as sole sulfur sources. Overall, PFPS is an excellent tool for isolating bacteria capable of cleaving subterminal C-S bonds within alkyl chains. The type of desulfurization displayed by JVH1 differs significantly from previously described reaction results.

Abstract  A new technological platform, based on the chemistry of the peroxidic perfluoropolyethers, has been recently developed for the synthesis of innovative fluorinated materials. Perfluoropolyether-tetrafluorethylene (PFPE-TFE) copolymers are one of the most representative examples of the potential and the flexibility of this technology. By tuning the reaction parameters, the structure of these copolymers can be easily modulated to obtain products with the desired chemical-physical and rheological properties. Applications are endless, from thin film lubrication to gel based greases, to additives for plastics, rubber and other compounds. This technology will lead to entirely new classes of PFPE materials that will fill many of the gaps existing today in markets not currently served by PFPEs. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Buff/Wipe (B/W) process is commonly used in disk drive manufacturing to remove the particles and asperities on the lubricated disk surface. In this paper, we investigated how B/W process impacts the physicochemical properties of perfluoropolyethers (PFPE) nano-films through the study of surface energy and bonded ratio. Two-liquid geometric method was used to analyze the surface energy of nonfunctional PFPE, i.e., Z03, and functional PFPE, i.e., Zdol, lubricated media before and after B/W process. It was found that the dispersive surface energy of Z03 films greatly decreased after B/W, which was more significant in the submonolayer regime. In addition, the bonded ratio slightly increased. However, B/W effect on the surface energy and bonded ratio was not detected for Zdol films. It is hypothesized that nonfunctional PFPE behaves liquid-like on the carbon overcoat due to the weak interaction between lubricant and overcoat. External mechanical stress as applied with B/W can change the conformation and increase the surface coverage for nonfunctional PFPE. On the other hand, functional PFPEs behave solid-like due to the strong attraction between lubricant and overcoat; therefore, it is difficult to change the conformation by external stress from B/W process. (C) 2014 AIP Publishing LLC.

Abstract  The dispersive and polar components of surface energy, which are typically obtained from the two-liquid geometric method through contact angle measurement, have been extensively used to study the interfacial properties of perfluoropolyether (PFPE) lubricated media used in hard disk drive industry. In this paper, an alternative approach, Lifshitz-van der Waals and Lewis acid-base (LW/AB) theory, which provides additional information on the nature of lubricant/overcoat interaction, has been applied to the study of the surface energy of PFPE-coated media. Here, the surface energy is decomposed into Lifshitz-van der Waals (LW), Lewis acid, and Lewis base components. The results of Lewis acid and Lewis base components of surface energy suggest that the bonding of functional PFPEs with a carbon overcoat is a Lewis acid-base interaction; the overcoat is an electron donor and functional PFPEs are electron acceptors. It was also found that the LW surface energy has a sequence of Ztetraol < Zdol < AM2001 < A20H < ZO3 for films with the same thickness, which is in the reverse sequence as found in the bonded thickness of these PFPEs. A molecular-level bonding mechanism is proposed to explain the experimental results.

Abstract  Quantitative determination of the molecular weight and composition of submicrogram quantities of a perfluorinated polyether (PFPE) supported on Ag and Si substrates was made from empirical relationships derived from the intensities of specific high-mass (greater-than-or-equal-to 800 amu) fragmentation ions from time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements. These relationships are explained in terms of simple concepts regarding the process of volatilization, fragmentation and ionization in TOF-SIMS. The results for both negative and positive ions are nearly independent of the substrate materials used, demonstrating that the high-mass fragmentation ions in TOF-SIMS may be useful generally for in situ quantitative analysis of PFPEs on non-specific substrates. This is an important difference between the TOF-SIMS fragmentation spectrum and the complementary TOF-SIMS cationized molecular ion spectrum, which requires special sample preparation and/or substrates. In order to interpret the quantitative information available in the TOF-SIMS fragment spectrum, it was absolutely necessary to characterize extensively the PFPE samples using NMR and TOF-SIMS Ag+-cationized molecular ion results. This characterization helped to demonstrate the power of TOF-SIMS to do quantitative analysis and led to additional insight concerning the SIMS ion-forming process for PFPE. This study represents one of the first attempts to make quantitative use of the high-mass fragment ion intensities in SIMS studies of polymers, and presents a method for confirming the origin of the mass peaks in the spectra.

Abstract  Although microfluidics represents a promising technology for drug screening industry and toxicity tests, their industrial applications using cells are limited by drawbacks of the weakly mass production capability of the biochips. In this work, we report the fabrication of resistant fluorinated microfluidic devices using a material widely used in polymer industries. To build the microdevices, two patterned layers with precise and regular microchannels were developed by photocuring of perfluoropolyethers (PFPEs). These layers were successfully sealed by UV irradiation. Then, Liver HepG2/C3A and kidney MDCK cells were cultured in PFPE biochips. The growth, cell viability and basal metabolism of cells cultured in PFPE biochips were studied and compared with results obtained using polydimethylsiloxane (PDMS) biochips. The results have shown that the cells can attach to the biochip bottom, spread, and proliferate well in PFPE biochip (similar to the cells in PDMS biochip). Furthermore, metabolisms of cell cultures in PFPE biochip, such as glucose consumption, albumin and urea productions, were proved similar to the results obtained in PDMS biochips. These results highlighted the functionality of the HepG2/C3A and MDCK cells in PFPE microfluidic devices and illustrated their potential to replace PDMS devices. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  The spreading characteristics of thin polymeric liquid films of perfluoropolyalkylethers (PFPEs) Fomblin Z15 and Fomblin Zdo1 (hydroxyl terminated PFPE) on silica surfaces have been measured by scanning microellipsometry (SME). We estimated the surface diffusion coefficients and propose a modified diffusion equation to interpret the spreading phenomenon from film thickness profiles measured with SME. We investigated the spreading of Z15 as a function of binary blend ratio of monodisperse Z15 fractions and found that the surface diffusion coefficients of the blends do not obey a simple linear mixing rule. A summary of thin PFPE film spreading characteristics as a function of molecular weight, film thickness, chain-end functionality, temperature, and humidity is presented. (C) 1996 American Institute of Physics.

Abstract  There have been a number of applications for lubricant additives in the disk drive media area, the first of which was for pseudo-contact recording with inductive heads (tri-pad sliders) in an effort to stabilize the head/disk interface and minimize lube decomposition under hot/wet conditions. A number of additives have been tried which include antioxidants as well as Lewis bases, the latter in an effort to passivate the catalytic activity of the Lewis Acid sites on the slider which results in the decomposition of the perfluoropolyether (PFPE) lubricants such as Z-Dol, AM and Z-Tetraol. In addition to this passivation action of the phosphazene toward catalytic decomposition of the lubricant, it has recently been reported that the use of X-1P (a cyclic phosphazene) also enhances reflow of the lube, increasing the durability of the head disk interface. In this regard there are still a number of unanswered questions that pertain to the mechanism of the interaction of the X-1P with the lubricant and/or carbon to cause this increase in mobility of the lubricant resulting in the enhanced durability.

There are numerous technical issues associated with the use of the various additives with the main one being compatibility between the additive and the PFPEs as well as the carbon surfaces on which they are coated. These issues include bonding, phase separation of the components, and the transfer mechanism for the additive to the slider where the passivation is required.

In this paper, we will look at the interaction of the X-1P with the carbon overcoat on the media in an effort to try to better understand the mechanism of such an interaction and its effect on the mobility of the lubricant as well as the amount of bonded lube on the disks. (C) 2002 Published by Elsevier Science Ltd.

Abstract  Perfluoropolyethers (PFPEs) have been investigated with Raman spectroscopy and density functional theory (DFT) calculations. The two dimensional correlation spectroscopy (2DCOS) approach has been applied to a set of PFPEs containing different concentrations of peroxide (-OO-) groups, thus allowing to evaluate the effect on the Raman spectra due to the presence of oxygen-oxygen bonds in the molecular structure. Careful analysis of the vibrational normal modes obtained with OFT calculations supports the detailed interpretation of the 2DCOS maps. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  During the intermittent contact between the head and the disk of the hard disk drive (HDD), the perfluoropolyether (PFPE) lubricant experiences shear/ elongation deformation. Therefore, the molecular rheology of PFPE becomes critically important in designing optimal lubricants that control the friction and wear. In this paper, we examine, for the first time, the rheological responses of nanoblended PFPEs, including storage and loss moduli (G' and G ''), by monitoring the time-dependent stress-strain relationship via nonequilibrium molecular dynamics simulations. We observed that the nonfunctional PFPEs (Fomblin Z-type) exhibit liquid-like behavior, while agglomeration behavior was observed for the functional PFPEs (Fomblin Zdol-type). In addition, strong endgroup couplings due to functional endgroup weaken as the temperature increases. For binary blended PFPEs, we also observed similar phenomena, which strongly depends on the blend ratio and imposed condition (e.g., temperature and oscillatory frequency). We established a finger print analysis via G'-G '' plots for different blend ratios and temperatures. By analyzing the blended PFPE relaxation processes, our results provide the optimal parameters for lubricant selection criteria to enhance the HDD performance.

Abstract  Heat assisted magnetic recording (HAMR) which locally reduces coercivity with a laser pulse, is currently the most promising technology to achieve areal density beyond 10 Tbit/in(2). However, due to the extreme operating condition of HAMR, the head-disk interface (HDI) suffers from extensive depletion and contamination of organic molecules. Our previous studies indicate that the conventional linear perfluoropolyether (PFPE) lubricants/grease molecules are not suitable for the severe thermal stress especially when coupled with external fields as the lubricant layer can be depleted and damaged. To simulate the molecular evaporation phenomena, we introduced novel multiscale modeling scheme, "Collection Of Spheres" model, which can predict mesoscale phenomena based on the atomistic/molecular level details via reduced order method. We have examined how the molecular architect affects evaporation under various degree of thermal stress (e.g., peak temperature and duration). Specifically, we examined several PFPEs (e.g., Z, Zdol, and Ztetraol) to study the effect of back-bone and end group properties on evaporation. Our multiscale model can provide holistic simulation of the HDI and provide molecular design criteria for HAMR device. (C) 2017 Author(s).

Abstract  Perfluoropolyethers (PFPEs) are widely used as lubricants on magnetic recording media. The mobility of the PFPE on the protective carbon overcoat of the media is widely accepted to be intimately coupled to the resulting tribological performance. The flow properties of molecularly thin films of nonpolar PFPE Z and polar PFPE Zdol functions on solid surfaces were investigated by measuring the spreading profiles. The spreading of Zdol exhibits terraced profiles with the formation of a molecular foot, a shoulder and a vertical step. To describe these features of Zdol spreading, we measured the Zdol thickness dependence of the surface energy, which is then used to calculate the thickness dependence of the disjoining pressure. The polar component of the Zdol surface energy exhibits oscillations as a function of PFPE thickness. The resulting oscillations in the disjoining pressure can be used to qualitatively describe the origins of terraced spreading. The characteristic Zdol spreading profile and surface energy oscillations of Zdol ave attributed to molecular layering induced by polar interactions between the Zdol end-groups and the surface.

Abstract  The thermodynamics of ultrathin (less than or equal to 10 Angstrom) perfluoropolyether (PFPE) films in contact with amorphous carbon surfaces (CHx and CNx) are derived from the time-dependent kinetics of film evaporation. Two nonfunctionalized PFPE structures were studied: a polydisperse (M-w/M-n = 1.4) Fomblin Z with an average molecular weight of 4000 g mol(-1) and a fractionated (M-w/M-n = 1.05) Demnum sample of average molecular weight 2200 g mol(-1). Data is also presented for the evaporation of a fractionated (M-w/M-n = 1.08) sample of the hydroxyl-terminated Fomblin Zdol (M-w = 2100 g mol(-1)). Evaporation of the nonfunctionalized PFPEs from amorphous carbon follows nonclassical, first-order desorption kinetics having a rate constant that varies inversely with time. Evaporation of the functionalized Fomblin Zdol is also nonclassical; however, the time dependence of the rate constant deviates substantially from that characteristic of the nonfunctionalized PFPEs. These evaporation kinetics result from the increase in the surface free energy that accompanies thinning of the PFPE film. An analytic expression for the dependence of the surface free energy on film thickness and temperature is derived from the time-dependent evaporation rate. In the Fomblin Z03 + CHx system, reasonable agreement is found between the functional form of the thickness-dependent surface free energy change determined from the evaporation kinetics and that obtained from previous contact angle measurements. The temperature dependence of the free energy is used to derive expressions for the entropy and the attractive potential energy of the confined liquid film. In the case of an ultrathin, completely wetting fluid, the magnitude of the attractive potential energy increases, and the film entropy decreases, with decreasing film thickness.

Abstract  Simultaneously oleophobic/hydrophilic coatings are highly desirable in many important applications, e.g., anti-fogging. However, to date, such coatings have been rarely reported and the underlying mechanisms remain unclear. In the current paper, the wetting behavior of three nanometer-thick perfluoropolyether (PFPE) polymers with the same backbone but different end-groups has been studied by contact angle tests and the underlying mechanisms governing the simultaneous oleophobicity/hydrophilicity have been investigated. The experimental results indicated that the end-groups of the nanometer-thick PFPEs are critical to the simultaneous oleophobicity/hydrophilicity. PFPE polymers with different end-groups can interact with the substrate in very different ways, resulting in different packing orders and thus different inter-chain distances within the polymer nanofilms. If the inter-chain distance is appropriately small, smaller water molecules penetrate the nanofilms quickly while larger oil molecules penetrate the nanofilms much more slowly. As a result, the surface shows a higher oil contact angle (OCA) than WCA, i.e., simultaneous oleophobicity/hydrophilicity. Moreover, the effect of simultaneous oleophobicity/ hydrophilicity on the long-term anti-fogging capability has been studied by X-ray photoelectron spectroscopy (XPS) and anti-fogging tests. The results indicated that the unique simultaneous oleophobicity/hydrophilicity reduces the airborne hydrocarbon contamination and therefore improves the long-term anti-fogging performance.

Abstract  Perfluoropolyethers (PFPEs) have been widely used as an excellent lubricant on magnetic disks. Sol-gel SiO2 has been applied as a protective overcoat for plated magnetic disks. Adsorption of PFPEs on the surface of a protective overcoat is an important issue in evaluating lubrication characteristics, such as coefficient of friction, wear resistance, volatility, spin-off, etc. for magnetic disks. Molecular configuration and magnitude of adsorption between lubricants and protective overcoats were measured, using various analytical methods, i.e., diffuse reflectance IR spectroscopy, polarization reflection IR spectroscopy, refractive index analysis, flow micro-calorimetry, etc. Functional groups in PFPE molecules adsorb to silanol groups on the sol-gel SiO2 surface. The main chain of PFPE molecule orients parallel to the sol-gel SiO2 surface. The thickness of adsorbed PFPE agrees well with the diameter of the PFPE main chain. The heat of adsorption increases with increasing hydrophilic affinity of functional groups. The heat of adsorption decreases with increasing baking temperature of sol-gel SiO2, which corresponds to the decrease in silanol group density.