Fluoropolymers: The Right Material for the Right Applications

Cross-Linking Strategies for Fluorine-Containing Polymer Coatings for Durable Resistant Water- and Oil-Repellency

Functional coatings for application on surfaces are of growing interest. Especially in the textile industry, durable water and oil repellent finishes are of special demand for implementation in the outdoor sector, but also as safety-protection clothes against oil or chemicals. Such oil and chemical repellent textiles can be achieved by coating surfaces with fluoropolymers. As many concerns exist regarding (per)fluorinated polymers due to their high persistence and accumulation capacity in the environment, a durable and resistant coating is essential also during the washing processes of textiles. Within the present study, different strategies are examined for a durable resistant cross-linking of a novel fluoropolymer on the surface of fibers. The monomer 2-((1,1,2-trifluoro-2-(perfluoropropoxy)ethyl)thio)ethyl acrylate, whose fluorinated side-chain is degradable by treatment with ozone, was used for this purpose. The polymers were synthesized via free radical polymerization in emulsion, and different amounts of cross-linking reagents were copolymerized. The final polymer dispersions were applied to cellulose fibers and the cross-linking was induced thermally or by irradiation with UV-light. In order to investigate the cross-linking efficiency, tensile elongation studies were carried out. In addition, multiple washing processes of the fibers were performed and the polymer loss during washing, as well as the effects on oil and water repellency were investigated. The cross-linking strategy paves the way to a durable fluoropolymer-based functional coating and the polymers are expected to provide a promising and sustainable alternative to functional coatings.

Surface Fluorination Modification and Anti-Biofouling Study of a pHEMA Hydrogel

A poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel film was prepared by bulk polymerization. Then, it was surface modified by perfluorooctanoyl chloride to improve the anti-biofouling properties. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDXS), and atomic force microscopy (AFM) analyses demonstrated that the uniform dense fluorinated layer had been successfully grafted onto pHEMA. The water contact angle (WCA) of the modified pHEMA film increased to 135°, while the surface energy decreased to 13.32 mN/m. The protein and bacterial adhesion properties of the modified pHEMA were decreased significantly. The in vitro cytotoxicity showed that the modified pHEMA was noncytotoxic. Thus, the fluorinated modification on the material surface was a convenient and effective method to establish a hydrophobic and anti-biofouling surface.

Vinylidene fluoride polymerization by metal-free selective activation of hydrogen peroxide: microstructure determination and mechanistic study

Hydrogen peroxide-initiated radical polymerization of vinylidene fluoride (VDF) at 130 °C in dimethyl carbonate is presented.

Facile synthesis of selenocarbamyl fluorides, selenoureas and their derivatives with [Me4N][SeCF3]

[Me4N][SeCF3] has proved to be an excellent precursor of Se=CF2 for amines in the preparation of selenocarbamoyl fluorides, selenoureas, and their derivatives under catalyst- and additive-free conditions, which are otherwise difficult to synthesize by other methods.

Recent advances in the preparation of semifluorinated polymers

Synthesis of semifluorinated polymers containing fluorous groups on the backbone or as side chains is an increasingly popular field of research.

Electrochemical tandem trifluoromethylation of allylamines/formal (3 + 2)-cycloaddition for the rapid access to CF3-containing imidazolines and oxazolidines

A straightforward and environmentally friendly synthesis of CF₃-containing imidazolines and oxazolidines has been developed through an electrochemical three-component reaction among allylamines, the Langlois reagent, and nitrile or carbonyl compounds.

Modification of polybutadiene with trifluoromethyl and clickable azide groups in one shot

We report copper-catalyzed intermolecular azide-trifluoromethylation of the alkenyls of PB without any chain degradation and crosslinking.

Fluoropolymers in biomedical applications: state-of-the-art and future perspectives

Biomedical applications of fluoropolymers in gene delivery, protein delivery, drug delivery, ¹⁹F MRI, PDT, anti-fouling, anti-bacterial, cell culture, and tissue engineering.

An overview of the uses of per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are of concern because of their high persistence (or that of their degradation products) and their impacts on human and environmental health that are known or can be deduced from some well-studied PFAS. Currently, many different PFAS (on the order of several thousands) are used in a wide range of applications, and there is no comprehensive source of information on the many individual substances and their functions in different applications. Here we provide a broad overview of many use categories where PFAS have been employed and for which function; we also specify which PFAS have been used and discuss the magnitude of the uses. Despite being non-exhaustive, our study clearly demonstrates that PFAS are used in almost all industry branches and many consumer products. In total, more than 200 use categories and subcategories are identified for more than 1400 individual PFAS. In addition to well-known categories such as textile impregnation, fire-fighting foam, and electroplating, the identified use categories also include many categories not described in the scientific literature, including PFAS in ammunition, climbing ropes, guitar strings, artificial turf, and soil remediation. We further discuss several use categories that may be prioritised for finding PFAS-free alternatives. Besides the detailed description of use categories, the present study also provides a list of the identified PFAS per use category, including their exact masses for future analytical studies aiming to identify additional PFAS.

An overview of the uses of per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are of concern because of their high persistence (or that of their degradation products) and their impacts on human and environmental health that are known or can be deduced from some well-studied PFAS. Currently, many different PFAS (on the order of several thousands) are used in a wide range of applications, and there is no comprehensive source of information on the many individual substances and their functions in different applications. Here we provide a broad overview of many use categories where PFAS have been employed and for which function; we also specify which PFAS have been used and discuss the magnitude of the uses. Despite being non-exhaustive, our study clearly demonstrates that PFAS are used in almost all industry branches and many consumer products. In total, more than 200 use categories and subcategories are identified for more than 1400 individual PFAS. In addition to well-known categories such as textile impregnation, fire-fighting foam, and electroplating, the identified use categories also include many categories not described in the scientific literature, including PFAS in ammunition, climbing ropes, guitar strings, artificial turf, and soil remediation. We further discuss several use categories that may be prioritised for finding PFAS-free alternatives. Besides the detailed description of use categories, the present study also provides a list of the identified PFAS per use category, including their exact masses for future analytical studies aiming to identify additional PFAS.

Foaming behavior of the fluorinated ethylene propylene copolymer assisted with supercritical carbon dioxide

Foaming behavior of the fluorinated ethylene propylene copolymer (FEP) and its composites assisted with supercritical carbon dioxide (scCO2) as the blowing agent were investigated. The batch foaming process was applied at temperature ranging from 250°C to 265°C and pressure ranging between 12 MPa and 24 MPa. The optimal foaming temperature and saturation pressure were obtained for both pure FEP and FEP composites with 1 wt% different-sized BaTiO3 as nucleating agent. The cell diameter of pure FEP foam ranging from 80–140 µm was observed while the cell diameter decreased to 20–40 µm after adding BaTiO3 particles. The cell density of foamed FEP with BaTiO3 increased significantly from 106 to 108 cells/cm3 and the expansion ratio ranged between 4.0 and 5.5. Moreover, a decrease in an abnormal phenomenon that expansion ratio for the pure FEP foam was observed as the saturation pressure increased. This unexpected phenomenon can be explained by the relationship between foaming and crystallization coupling processes.

Vinyl ethers and epoxides photoinduced copolymerization with perfluoropolyalkylether monomers

New perfluoropolyalkylether (PFPAE) monomers, chain extended with different alkyl groups and functionalized with vinyl ether or epoxide end-groups, were employed, together with trimethylolpropane trivinyl ether or trimethylolpropane triglycidyl ether, to produce fluorinated copolymers. The photoinduced cationic polymerization was investigated, and the PFPAE-based copolymer properties were thoroughly characterized. Interesting surface properties and two different values of refractive index were observed: thus, these fluorinated copolymers can be suitable materials for the manufacture of self-cleaning coatings and optical waveguides.

Studies of Langmuir and Langmuir-Schaefer Films of Poly(3-Hexylthiophene) and Poly(Vinylidene Fluoride)

The synergistic use of blends of regioregular poly(3-hexylthiophene) (P3HT) and poly(vinylidene fluoride) (PVDF) or poly((vinylidene fluoride)-block-(methyl methacrylate)) (PVDF-PMMA) to form Langmuir and Langmuir-Schaefer (LS) films is reported. P3HT has wide applications in sensor devices because of its properties such as conductivity, luminescence, and chromism; however, the stiffness of the films and the difficulty in organizing the molecules may pose a problem in these applications. In this context, polymers based on PVDF can be used in the formation of thin P3HT films and present an alternative to improve the organization of P3HT molecules. In addition, PVDF acts as a plasticizer, making the film less rigid. The films were obtained from the blends of P3HT/PVDF and P3HT/PVDF-PMMA in a solution containing chloroform and DMAc (N,N-dimethylacetamide). Surface pressure isotherms, in situ ultraviolet-visible (UV-vis) spectroscopy, polarization-modulation infrared reflection-absorption spectroscopy, and Brewster angle microscopy techniques were used to analyze Langmuir films. The surface morphology of LS films was characterized by atomic force microscopy and UV-vis spectroscopy, and their degradation was analyzed by UV-vis spectroscopy after exposure to natural light under atmospheric conditions. The Langmuir films containing PVDF indicate a direct formation of the ferroelectric β phase, with dipoles parallel to the water surface. The Langmuir films formed by P3HT presented dipoles of side chains parallel and aromatic groups perpendicular to the water surface. P3HT and PVDF or PVDF-PMMA films show high molecular organization compared with pure P3HT films. The results suggest that these films could be used to improve the properties of P3HT in several device applications, such as in optical and electrical sensors.

Fluoropolymer Nanoparticles Prepared Using Trifluoropropene Telomer Based Fluorosurfactants

A fluorosurfactant based on 3,3,3-trifluoropropene (TFP) telomer was synthesized as an environmentally friendly alternative to perfluorooctanoic acid (PFOA) using TFP and 2-iodoperfluoropropane ((CF₃)₂CF-I) as starting materials. TFP telomerization was initiated by addition of di-tert-butylperoxide in the presence of (CF₃)₂CF-I as a chain transfer agent. The surfactant was obtained by modification of the iodine end-group on the TFP telomer to form an allylic functionality followed by the addition of thioglycolic acid via a thiol-ene reaction. The resulting fluorosurfactant exhibited a lower critical micellar concentration (CMC = 0.87 g·L^-1) than that of PFOA (CMC = 3.0 g·L^-1). This surfactant was used to prepare fluoropolymer nanoparticles by solvent evaporation from a solution composed of the surfacant and poly[2-(perfluorobutyl)ethyl methacrylate]. The oil-in-water emulsion was initially formed due to the adsorption of the surfactant molecules at the oil/water interface and subsequently converted into a nanoparticle suspension after solvent evaporation. Because of the strong hydrophobic interactions between the fluorinated surfactant tail and fluoropolymer, the obtained nanoparticle suspension was quite stable against water dialysis.

Investigations into CTA-differentiation-involving polymerization of fluorous monomers: exploitation of experimental variances in fine-tuning of molecular weights

Condition and substrate effects on CTA-differentiation-involving polymerization were explored for logical control of molecular weight.

Investigating the effect of grafting density on the surface properties for sequence-determined fluoropolymer films

Six sequence-determined fluoropolymers were synthesized and their surface properties were affected by their grafting densities. The reason can be attributed to the assembled structure of the perfluoroalkyl chains at the surface.

Synthesis of fluorinated polyethylene of different topologies via insertion polymerization with semifluorinated acrylates

Fluorinated polyethylene with different topologies can be generated via insertion polymerization with various late-transition-metal catalysts.

Preparation and electroactive phase adjustment of Ag-doped poly(vinylidene fluoride) (PVDF) films

The crystallinities of Ag-doped poly(vinylidene fluoride) (PVDF) films were modified by removing Ag⁺ using a novel washing process, which allowed control of the ratio of γ- and β-phases. The polarity of the composite film without Ag⁺ removal through the washing process reached 98%, and the β-phase content in the total electroactive phase was increased to 61%, according to Fourier-transform infrared spectroscopy. When Ag⁺ were removed through a process involving several cycles of washing, filtering, drying, and re-dissolving, the highest ratio of the γ-phase was increased to 67%, 28% higher than that before washing. This showed that Ag⁺ induced β-phase formation while Ag nanoparticles induced γ-phase formation, and that the ratio of γ- and β-phases in PVDF composite films can be controlled to suit specific applications by this washing process.

Precise Synthesis of Ultra-High-Molecular-Weight Fluoropolymers Enabled by Chain-Transfer-Agent Differentiation under Visible-Light Irradiation

Ultra-high-molecular-weight (UHMW) polymers display outstanding properties and hold potential for wide applications. However, their precise synthesis remains challenging. Herein, we developed a novel reversible-deactivation radical polymerization based on the strong and selective fluorine-fluorine interaction, allowing chain-transfer agents to spontaneously differentiate into two groups that take charge of the chain growth and reversible deactivation of the growing chains, respectively. This method enables dramatically improved livingness of propagation, providing UHMW polymers with a surprisingly narrow molecular weight distribution (Đ≈1.1) from a variety of fluorinated (meth)acrylates and acrylamide at quantitative conversions under visible-light irradiation. In situ chain-end extensions from UHMW polymers facilitated the synthesis of well-defined block copolymers, revealing the excellent chain-end fidelity achieved by this method.

Iron-Catalyzed Atom Transfer Radical Polymerization of Semifluorinated Methacrylates

Fluorinated polymers are an important class of functional materials that exhibit unique properties such as high chemical resistance, thermal stability, and low surface energy. Atom transfer radical polymerization (ATRP) of semifluorinated monomers catalyzed by copper catalysts often requires development of special conditions to control the polymerization and prevent side reactions such as base-catalyzed transesterification between the fluoro-containing monomers and solvents. In this paper, photoinduced iron-catalyzed ATRP was applied to the polymerization of a variety of semifluorinated methacrylate monomers. Polymerizations were initiated by photochemical generation of the Fe catalyst activator under blue light irradiation, enabling temporal control over the growth of polymer chains, and were well-controlled in various solvents, including fluorinated and nonfluorinated solvents, without undergoing any side reactions. Moreover, in situ chain extension and block copolymerization experiments demonstrated the preservation of chain end functionality, enabling facile synthesis of well-controlled block copolymers.

Fluorinated Titania Nanoparticle-Induced Piezoelectric Phase Transition of Poly(vinylidene fluoride)

We prepared F-coated rutile titanium dioxide nanoparticles (r-TiO₂ NPs) via simple thermal annealing of titania NPs in poly(vinylidene fluoride) (PVDF) and demonstrated that the F-coated r-TiO₂ NP-doped composite film could efficiently induce piezoelectric phase transition of non-electroactive PVDF due to highly electronegative F bonds on the surface of these NPs. In the case of a 2.0 wt % composite film, 99.20% of the non-electroactive PVDF was transformed into the electroactive phase. Additionally, utilizing the F-coated r-TiO₂ NPs for a piezoelectric device led to an enhancement of the piezoelectric performance. With the 5.0 wt % composite film, the resulting piezoelectric device exhibited voltage generation of 355 mV, whereas a device with the innate r-TiO₂ NPs exhibited voltage generation of only 137 mV. Furthermore, because of optical inactivity of F-coated r-TiO₂ NPs, the piezoelectric films exhibited high stability under 64 h of photoirradiation at an intensity of 0.1 W/cm². These results indicate that the F-coated r-TiO₂ NP-doped composite films could be useful for various applications, including outdoor energy-harvesting, self-powered wearable devices, and portable sensors.

Preparation and dielectric properties of poly(acrylonitrile-co-2,2,2-trifluoroethyl methacrylate) materials via radical emulsion copolymerization

Radical emulsion copolymerization of acrylonitrile (AN) with 2,2,2-trifluoroethyl methacrylate (MATRIF) and their homopolymerization initiated by potassium persulfate (KPS) were studied.

Aromatic fluorocopolymers based on α-(difluoromethyl)styrene and styrene: synthesis, characterization, and thermal and surface properties

A study on the α-(difluoromethyl)styrene (DFMST) reactivity under conventional radical copolymerization conditions is presented. Although the homopolymerization of DFMST failed, its radical bulk copolymerization with styrene (ST) led to the synthesis of fluorinated aromatic polymers (FAPs). The resulting novel poly(DFMST-co-ST) copolymers were characterized by 1H, 19F and 13C NMR spectroscopies that evidenced the successful incorporation of DFMST units into copolymers and enabled the assessment of their respective molar percentages (10.4-48.2 mol%). The molar masses were in the range of 1900-17 200 g mol-1. The bulkier CF2H group in the α-position induced the lower reactivity of the DFMST comonomer. ST and DFMST monomer reactivity ratios (r DFMST = 0.0 and r ST = 0.70 ± 0.05 at 70 °C) were determined based on linear least-square methods. These values indicate that DFMST monomer is less reactive than ST, retards the polymerization rate, and thus reduces the molar masses. Moreover, the thermal properties (T g, T d) of the resulting copolymers indicate that the presence of DFMST units incorporated into poly(ST) structure promotes an increase of the T g values up to 109 °C and a slightly better thermal stability than that of poly(ST). Additionally, the thermal decomposition of poly(DFMST-co-ST) copolymer (10.4/89.6) was assessed by simultaneous thermal analysis coupled with Fourier-transform infrared spectroscopy and thermogravimetric analysis coupled with mass spectrometry showing that H2O, CO2, CO and styrene were released. The surface analysis was focused on the effects of the -CF2H group at the α-position of styrene comonomers on surface free energy of the copolymer films. Water and diiodomethane contact angle (CA) measurements confirmed that these copolymers (M n = 2300-17 200 g mol-1) are not exactly the same as polystyrenes (M n = 2100-21 600 g mol-1) in the solid state. The CA hysteresis for poly(ST) (6-8°) and poly(DFMST-co-ST) copolymers (3-5°) reflected these differences even more accurately.