Fluorinated Block Copolymers Research Articles

Proton-conducting phosphotungstic acid/sulfonated fluorinated block copolymer composite membrane for polymer electrolyte fuel cells with reduced hydrogen permeability

A sulfonated fluorinated block copolymer (SFBC) consisting of sulfone and ether bridges was synthesized via nucleophilic substitution polymerization, and then incorporated with 10, 20 or 30 wt% of phosphotungstic acid (PWA) using facile solution casting approach to fabricate composite membranes. The monomer sulfonation was carried out for SFBC to avoid the random sulfonation that can degrade the mechanical strength of polymer chains. A higher local concentration of acidic moieties within molecular frameworks of PWA and good mechanical properties allow for an unprecedented approach to tailor the proton conductivity as well as mechanical strength of composite membrane, as evidenced by alternating current (AC) impedance and dynamic mechanical (DMA) analyses. The surface morphological properties and roughness of membranes were investigated by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM); the composite membranes exhibited even and denser dispersion of PWA in polymer matrix. Compared to pristine SFBC-50, the water uptake, hydrophilicity and ion exchange capacity of SFBC-50/PWA-X membranes were significantly improved. The peak proton conductivity of SFBC-50/PWA-30 membrane at 90 °C under 100% relative humidity (RH) is 105.22 mS/cm, which is 2.55 folds higher than that of pristine SFBC-50 (41.11 mS/cm) and 1.2 folds lower than that of Nafion-117 membrane (127.12 mS/cm). The peak power density delivered by the PEFC containing SFBC-50/PWA-30 membrane is 377.83 mW/cm2 at a load current of 864.29 mA/cm2 while operating the cell at 60 °C under 100% RH. In contrast, under identical condition, the pristine SFBC-50 membrane delivered the peak power density of 147.37 mW/cm2 at a load current of 353.52 mA/cm2, a 2.56-fold lower performance compared to composite membrane. Furthermore, composite membrane exhibited much lower H2 permeability compared to that of SFBC-50 and Nafion-117 membrane.

Artificially designed, low humidifying organic–inorganic (SFBC-50/FSiO2) composite membrane for electrolyte applications of fuel cells

Abstract The composite membranes composed of sulfonated fluorinated block copolymer (SFBC-50) having the degree of sulfonation (DS) of 50% and 3, 6, 9, 12 or 15 wt% functionalized silica (FSiO 2 ) were prepared by facile solution casting method. SFBC-50 was synthesized via nucleophilic substitution polymerization reaction, where the hydrophilic units are di-sulfonated poly arylene ether sulfone and the hydrophobic units are fluorinated polyarylene perfluoropropane biphenyl. The simple, but effective functionalization of SiO 2 is performed by fuming chlorosulfonic acid in order to increase the per unit volume of sulfonate (-SO 3 H) groups on SiO 2 surface. The ability of FSiO 2 particles afforded an unprecedented approach to simultaneously tune up the physio-chemical properties and mechanical strength of the composite membrane, which are evidenced by the results of water uptake measurement and dynamic mechanical analysis (DMA). Several characterization techniques, include FE-SEM, AFM, 1 H-NMR, FT-IR, DSC, XRD and UTM, DMA, were exploited in order to gain insights on the morphology, chemical structure, intermolecular bond stretching, glass transition temperature, crystallinity and mechanical properties of the samples. The proton conductivity of pristine SFBC-50 membrane at 90 °C under 40% relative humidity (RH) is 6.9 mS/cm, which is lower by 1.91 times than that of membrane containing 12 wt% of FSiO 2 (13.2 mS/cm). In contrast, under identical operating conditions, the Nafion-117 membrane showed the conductivity of 8.1 mS/cm, a 1.6 fold lower conductivity compared to that of the prepared composite membrane. Furthermore, the composite membrane revealed a much lower H 2 gas permeability than those of pristine SFBC-50 and Nafion-117 membrane.

Novel Fluorinated Polymer-Mediated Upconversion Nanoclusters for pH/Redox Triggered Anticancer Drug Release and Intracellular Imaging

This paper designs and synthesizes a novel amphiphilic fluorinated block copolymer, composed of oligo ethylene glycol methyl ether methacrylate, 2-(N,N-dimethylamino)ethyl methacrylate, and developing 2-((2-methacryloyloxy ethyl) disulfanyl) ethyl 3,5-bis(trifluoromethyl) benzoate, by reversible addition–fragmentation chain transfer polymerization. This amphiphilic block copolymer can self-assemble with hydrophobic lanthanide-based upconversion nanoparticles to form hybrid colloidal nanoclusters. The obtained nanoclusters exhibit not only good water-dispersibility, high biocompatibility, and strong stability in biological milieu, but excellent pH/redox-dual-responsive release in vitro behavior for doxorubicin (DOX). And the DOX-loaded nanoclusters have much better therapeutic effect than free DOX and can be uptaken by MCF-7 cells with evident upconversion luminescence signal for intracellular imaging.

Synthesis of fluorinated nanoparticles via RAFT dispersion polymerization-induced self-assembly using fluorinated macro-RAFT agents in supercritical carbon dioxide

Nano-sized fluorinated block copolymer particles are prepared by RAFT dispersion polymerization with polymerization-induced self-assembly proceeding in supercritical carbon dioxide.

Synthesis of fluorinated block copolymer and superhydrophobic cotton fabrics preparation

Abstract Fluorinated block copolymers, hexafluorobutyl methacrylate-block-poly(glycidyl methacrylate) (HFBMA- b -PGMAs, FPGs) were synthesized by atom transfer radical polymerization (ATRP) and applied to fabricating hydrophobic cotton fabrics. Since the HFBMA block provided low surface free energy and the PGMA blocks served as anchors with cotton fibers, the FPGs modified cotton fabrics showed excellent water repellency. The results indicated that nano- and microscale rough structures were created with combining HFBMA blocks onto surfaces of micro-sized cotton fibers. Since the HFBMA blocks were chemically bound to the cotton fibers by epoxy groups of PGMA blocks, the modified cotton fabrics possessed long-term high stability and durability. Furthermore, the important cotton fabric parameters such as tensile strength, color, and haptics were all unaffected by the FPGs modification, which revealed potential for applications.

Amphiphilic Fluorinated Block Copolymer Synthesized by RAFT Polymerization for Graphene Dispersions.

Despite the superior properties of graphene, the strong π–π interactions among pristine graphenes yielding massive aggregation impede industrial applications. For non-covalent functionalization of highly-ordered pyrolytic graphite (HOPG), poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinyl pyridine) (PTFEMA-b-PVP) block copolymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and used as polymeric dispersants in liquid phase exfoliation assisted by ultrasonication. The HOPG graphene concentrations were found to be 0.260–0.385 mg/mL in methanolic graphene dispersions stabilized with 10 wt % (relative to HOPG) PTFEMA-b-PVP block copolymers after one week. Raman and atomic force microscopy (AFM) analyses revealed that HOPG could not be completely exfoliated during the sonication. However, on-line turbidity results confirmed that the dispersion stability of HOPG in the presence of the block copolymer lasted for one week and that longer PTFEMA and PVP blocks led to better graphene dispersibility. Force–distance (F–d) analyses of AFM showed that PVP block is a good graphene-philic block while PTFEMA is methanol-philic.

Synthesis of fluorinated block copolymer electrolyte containing quaternary ammonium base

Fluorinated block copolymers poly(2,3,4,5,6-pentafluorostyrene)-b-poly(styrene) (PFS-b-PS) synthesized by atom transfer radical polymerization was functionalized with quaternary ammonium base groups via chloromethylation of PFS-b-PS, followed by reactions with trimethylamine and ion exchange with KOH to prepare anion exchange block polymer electrolytes (AEBPEs). The challenges and limitations during the synthesis are discussed. A comparative study on the chloromethylation of PFS-b-PS with two kinds of chloromethylation agents is carried out. The thermal stability, morphology, and conductivity of the obtained AEBPEs (PFS-b-QAPS(OH)) were investigated by thermogravimetry analysis, differential scanning calorimeter, small-angle X-ray scattering, and AC impedance, respectively.

Transparent superhydrophobic coatings from amphiphilic-fluorinated block copolymers synthesized by aqueous polymerization-induced self-assembly

Preparation of transparent and superhydrophobic coatings by co-deposition of an aqueous solution of an amphiphilic fluorinated block copolymer with silica was developed.

Block copolymers with stable radical and fluorinated groups by ATRP

Abstract

Non-Biofouling Fluorinated Block Copolymer Coatings for Contact Lenses

Non-Biofouling Fluorinated Block Copolymer Coatings for Contact Lenses

Mn2(CO)10-photomediated synthesis of poly(vinylidene fluoride)-b-poly(styrene sulfonate)

Mn2(CO)10-photomediated activation of perfluoro alkyl iodides under visible light was applied in the initiation of the polymerization of neopentyl styrene sulfonate (NeoSS) and of vinylidene fluoride (VDF). In the latter case, an iodine degenerative controlled radical polymerization also enabled the synthesis of PVDF-I with high chain end functionality, suitable for block copolymer synthesis. As such, quantitative Mn2(CO)10 activation of both PVDFCH2CF2I and PVDFCF2CH2I chain ends enabled the clean synthesis of PVDF-b-PNeoSS block copolymers. While subsequent deprotection of the neopentyl group was attempted by several methods, pure thermal decomposition was revealed to be more of a surface process, and while both (CH3)3SiI and LiBr deprotections failed, NaN3 in dimethyl sulfoxide was proven to allow for a complete removal of the protecting group to cleanly afford PVDF-b-PSSNa. These procedures provide simpler, cleaner and powerful avenues towards the synthesis of well-defined sulfonated and fluorinated block copolymers for fuel cell membranes.

Enhancing the low surface energy properties of polymer films with a dangling shell of fluorinated block-copolymer

Stabilizing long-term, low energy surface properties is a key issue in designing fluorinated polymer network, because the fluorinated surface could reorganize or hydrolyze upon contact with water. Here we report an exploring to enhance the low energy surface performance by bonding a dangling shell of fluorinated block copolymer, poly((1H,1H,2H,2H-perfluorodecyl acrylate)-b-poly(caprolactone) (PFDA-b-PCL)), to the polyurethane network. The PFDA and PCL block are the fluorinated shell and the dangling chain, respectively. The fluorinated shell protects the surface from rearrangements and hydrolysis when in contact with water, while the soft polyester block provides the required flexibility for fluorinated components to segregate to the surface. Surfaces with water contact angle up to 120° and surface energy down to 18mN/m were obtained. We then evaluated the effects of fluorinated species on the surface properties of the polyurethane network both with and without the fluorinated shell or polyester spacer. The surfaces functionalized with the fluorinated dangling shell are highly hydrophobic and exhibited better hydrophobic stability. The oligoester spacer connecting the fluorinated shell to the polymer network is critical for the segregation and rebuilding of low energy surfaces.

Synthesis and characterization of sulfonated fluorinated block copolymer membranes with different esterified initiators for DMFC applications

ABSTRACTThis investigation studied the synthesis of ionic membranes composed of a sulfonated poly(styrene‐isobutylene‐styrene) with novel fluoroblock copolymers. These fluoroblock copolymers were synthesized using three different initiators by Atom Transfer Radical Polymerization (ATRP); two fluoroinitiators were obtained from the esterification of 2‐(perfluoroalkyl) ethanol or octafluoro 4‐4′‐biphenol. The third initiator evaluated was 1‐bromoethyl benzene. The resulting block copolymers were characterized using several techniques: Gel Permeation Chromatography, Nuclear Magnetic Resonance, Fourier Transform Infrared Spectroscopy, Ultraviolet Spectroscopy, Thermogravimetric Analysis, and Differential Scanning Calorimetry. Transport properties (e.g., proton conductivity and methanol permeability) were measured to evaluate their performance for direct methanol fuel cell (DMFC). The choice of ATRP initiator was found to have a profound impact on the thermal stability of the different homopolymers and block copolymers studied. In addition, the chemical nature and symmetry of the initiators can lead to different chemical and electronic transitions, which influence the performance of these ionic membranes in applications such as proton exchange membranes for DMFC applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42046.

Energy Transfer Induced by Carbon Quantum Dots in Porous Zinc Oxide Nanocomposite Films

A one-pot approach making use of a zinc oxide sol precursor and carbon quantum dots, together with a partially fluorinated block copolymer as templating agent, has been used to synthesize a porous matrix characterized by interesting energy transfer properties. The choice of the fluorinated surfactant for inducing the porosity into the inorganic matrix has allowed an easy removal of the templating agent at low temperature, preserving at the same time the functional properties of the carbon quantum dots. The resulting nanocomposite films have been characterized by steady-state 3D mapping that has evidenced a complex behavior as a function of the carbon quantum dots concentration. In particular, the luminescence bands of the zinc oxide matrix appear to be modulated by the broad emission of the carbon quantum dots, which depends on their aggregation state. These results can be thus considered as a step further toward the fine-tuning of the luminescence properties provided by zinc oxide-based nanocomposites as a result of a doping effect due to the presence of carbon quantum dots.

Copolymer architecture effects on the morphology and surface performance of epoxy thermosets containing fluorinated block copolymers

ABSTRACTThe architecture effects on phases and surface enrichment behaviors of epoxy nanocomposites containing fluorinated block copolymers are investigated by the incorporation of two novel copolymers composed of poly (2, 2, 2‐trifluoroethyl methacrylate) (PTFEMA) and poly (ε‐caprolactone) (PCL), PCL‐b‐PTFEMA and PTFEMA‐b‐PCL‐b‐PTFEMA, with identical molecular weight and composition. These fluorinated copolymers in epoxy display distinguished self‐assembled structures, as evidenced by dynamic laser scattering and scanning electron microscopy measurements. Static contact angle detection suggests that the nanocomposites display an obvious improvement in surface water repellency and a reduction in surface free energy. The enhancement in surface hydrophobicity is attributed to the enrichment of PTFEMA blocks at the nanocomposite surface and to the formation of the specific surface morphology, as confirmed by atomic force microscopy. The different architectures of the two block copolymers give rise to differences in phase‐structures, and the ultimate surface performances of composites. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1037–1045

Preparation of polystyrene latex particles by miniemulsion polymerization using a predissolved fluorinated block copolymer as the sole co-stabilizer

The fluorinated block copolymer [P(St-b-DFM)] of styrene (St) and dodecafluoroheptyl methacrylate (DFM) was used as the sole co-stabilizer in St miniemulsion instead of the conventional co-stabilizers. The fluorinated block copolymer was prepared by atom transfer radical polymerization (ATRP). The fluorine content in P(St-b-DFM) was determined based on the relative number–average molecular weight of the macroinitiator and P(St-b-DFM). In St miniemulsion polymerization, the effects of the fluorine content in the block polymer on the size and number of the initial monomer droplets and latex particles were investigated. The ratio of the final number of latex particles to the initial number of monomer droplets was used to discuss the nucleation mechanism. The P(St-b-DFM) copolymers with 6% and 11% fluorine contents had a better effect on the stability of the monomer droplets, and monomer droplet nucleation almost dominated the process of St miniemulsion polymerization. The water contact angle on the surface of the polystyrene latex film demonstrated the surface hydrophobicity, and the surface tension was estimated according to Girifalco–Good–Fowkes–Young equation.

Synthesis and characterization of rubbery highly fluorinated siloxane-imide segmented copolymers

The synthesis and characterization of a series of poly(siloxane–imide) block (or segmented) copolymers obtained by copolymerization of amine-terminated polydimethylsiloxane with fluorinated aromatic compounds containing anhydride and amine functionality are reported. New fluorinated block copolymers have been synthesized to obtain organophilic polyimides potentially interesting for molecular membrane separations. The new aspects of this work relative to the literature are (1) a comparison of solution and solid-state approaches in the imidization step to generate the target poly(siloxane–imide) copolymers and (2) exploration of new compositions involving fluorinated aromatic polymers derived from added diamine compounds. It is shown that the copolymer properties can be tailored from glassy to rubbery materials by varying the amount and the type of oligosiloxane used; the transition between glassy and rubbery properties is characterized at a siloxane content of 60 wt%. As a main result, it is shown that the solid-state approach for inducing the cyclo-imidization step is the more efficient one for synthesizing polymers with good mechanical properties, when the amount of siloxane block is increased in the copolymer series. Physical and chemical methods (thermogravimetric analysis, Fourier transform infrared spectroscopy, viscosity measurements) were used to characterize the copolymer properties obtained according to the two different synthesis routes. The obtained siloxane–imide copolymers are well soluble in a large variety of moderately polar solvents and exhibit very good thermal stability up to 400 °C. Hence the prepared copolyimides would seem to be promising candidates as organophilic membranes as well as gas permeation membranes. © 2012 Society of Chemical Industry

Effect of Solvent Quality on the Solution Properties of Assemblies of Partially Fluorinated Amphiphilic Diblock Copolymers

The effect of solvent on the formation of assemblies of partially fluorinated block copolymers in solution has been examined. Two classes of materials based respectively on 2,2,2-trifluoroethyl acrylate (TFEA) and 2,2,2-trifluoroethyl methacrylate (TFEMA) were dissolved in organic solvents, and the properties on successive addition of water were studied using NMR spectroscopy, NMR imaging, AFM, and TEM. The relatively high glass transition temperature of the methacrylate blocks resulted in the formation of kinetically trapped structures that could only be resolved following heating to temperatures well above the Tg. The acrylate polymers formed loose assemblies in pure dimethylformamide, and on addition of water cylindrical micelles were observed. On the other hand, in pure acetone the partially fluorinated segments interacted more strongly with the solvent, with this structure inverting on addition of water. The NMR parameters were strongly dependent on the proposed structures in solution, and most marke...

Investigation of the nanocellular foaming of polystyrene in supercritical CO2 by adding a CO2‐philic perfluorinated block copolymer

AbstractNanocellular foaming of polystyrene (PS) and a polystyrene copolymer (PS‐b‐PFDA) with fluorinated block (1,1,2,2‐tetrahydroperfluorodecyl acrylate block, PFDA) was studied in supercritical CO2 (scCO2) via a one‐step foaming batch process. Atom Transfer Radical Polymerization (ATRP) was used to synthesize all the polymers. Neat PS and PS‐b‐PFDA copolymer samples were produced by extrusion and solid thick plaques were shaped in a hot‐press, and then subsequently foamed in a single‐step foaming process using scCO2 to analyze the effect of the addition of the fluorinated block copolymer in the foaming behaviour of neat PS. Samples were saturated under high pressures of CO2 (30 MPa) at low temperatures (e.g., 0°C) followed by a depressurization at a rate of 5 MPa/min. Foamed materials of neat PS and PS‐b‐PFDA copolymer were produced in the same conditions showing that the presence of high CO2‐philic perfluoro blocks, in the form of submicrometric separated domains in the PS matrix, acts as nucleating agents during the foaming process. The preponderance of the fluorinated blocks in the foaming behavior is evidenced, leading to PS‐b‐PFDA nanocellular foams with cell sizes in the order of 100 nm, and bulk densities about 0.7 g/cm3. The use of fluorinated blocks improve drastically the foam morphology, leading to ultramicro cellular and possibly nanocellular foams with a great homogeneity of the porous structure directly related to the dispersion of highly CO2‐philic fluorinated blocks in the PS matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Nanocellular foaming of fluorine containing block copolymers in carbon dioxide: the role of glass transition in carbon dioxide

Carbon dioxide foaming in polymeric materials has been recognized as an environmentally friendly method to introduce microfoam consisting of cells of micrometre size (microcells). Our group has demonstrated that CO2-philic fluorinated block domains of block copolymers worked as nuclei of foams and further decreased the size of cells to around 10 nm (nanocells). In this study, we introduced nanocells to poly[(methyl methacrylate)-b-(perfluorooctylethyl methacrylate)] (PMMA–PFMA, MF) and poly[(perfluorooctylethyl methacrylate)-b-(methyl methacrylate)-b-(perfluorooctylethyl methacrylate)] (PFMA–PMMA–PFMA, FMF), and compared the resultant porosity with those of polystyrene-based fluorinated block copolymers previously studied. The temperature providing a maximum porosity for the PMMA based copolymers was lower than that for the PS based copolymers. We further measured the glass transition temperatures, Tg, of skeleton blocks, i.e. PS and PMMA, in the presence of CO2 using a quartz crystal resonator and revealed that the temperature of maximum porosity is correlated to the decreased Tg of the skeleton polymers in CO2.