Fluoropolymer Nanoparticles Synthesized via Reversible-Deactivation Radical Polymerizations and Their Applications

Fluorinated polymeric nanoparticles (FPNPs) combine unique properties of fluorocarbon and polymeric nanoparticles, which has stimulated massive interest for decades. However, fluoropolymers are not readily available from nature, resulting in synthetic developments to obtain FPNPs via free radical polymerizations. Recently, while increasing cutting-edge directions demand tailored FPNPs, such materials have been difficult to access via conventional approaches. Reversible-deactivation radical polymerizations (RDRPs) are powerful methods to afford well-defined polymers. Researchers have applied RDRPs to the fabrication of FPNPs, enabling the construction of particles with improved complexity in terms of structure, composition, morphology, and functionality. Related examples can be classified into three categories. First, well-defined fluoropolymers synthesized via RDRPs have been utilized as precursors to form FPNPs through self-folding and solution self-assembly. Second, thermally and photoinitiated RDRPs have been explored to realize in situ preparations of FPNPs with varied morphologies via polymerization-induced self-assembly and cross-linking copolymerization. Third, grafting from inorganic nanoparticles has been investigated based on RDRPs. Importantly, those advancements have promoted studies toward promising applications, including magnetic resonance imaging, biomedical delivery, energy storage, adsorption of perfluorinated alkyl substances, photosensitizers, and so on. This Review should present useful knowledge to researchers in polymer science and nanomaterials and inspire innovative ideas for the synthesis and applications of FPNPs.

A Review: Per- and Polyfluoroalkyl Substances-Biological Degradation

Per- and polyfluoroalkyl substances (PFASs), highly stable synthetic organic compounds with multiple carbon-fluorine bonds, are emerging as environmental contaminants, toxic, bioaccumulative, and environmentally persistent. PFASs are strongly resistant to biological and chemical degradation, and therefore PFASs present a challenge to researchers and scientists for a better understanding and application of remediation methods and biodegradation of PFASs and have become subject to strict government regulations. The review summarizes the recent knowledge of bacterial and fungal degradation of PFASs, as well as the enzymes involved in the processes of transformation/degradation of PFASs.

Fabrication of graphene-oxide and zeolite loaded polyvinylidene fluoride reverse osmosis membrane for saltwater remediation

Incorporation of inorganic and organic materials in polymer has contributed well towards the development of advanced reverse-osmosis membranes; with greater permeation, and salt rejection potential. We are reporting, Zeolite/GO/PVDF based thin-film composite membranes that were successfully synthesized by solution casting process, an eco-friendly, low-cost, and biocompatible technique. PVDF membranes modified with different ratios of GO/Zeo (0.03, 0.05 and 0.07) were characterized by FTIR, SEM, XRD, TGA, and DSC. Membranes were then tested for its potential for water permeation and salt rejection abilities. As prepared membranes owe better pore-distribution, a moderate degree of crystallinity and high absorption capability that is highly needed for micro-filtration phenomena used for desalination of saline water. The modified membranes exhibited enhanced water permeability up to 28.9 L/m²h as compared to pure PVDF membrane having water permeability flux of 15.6 L/m²h. Salt-rejection ability was found increasing for the membranes (up to 98%) modified with different concentration of GO/Zeo, as compare to pure PVDF membrane (82%). During water permeation and salt rejection studies, no deleterious impact was noted for modified PVDF membranes. This development will entail an efficient approach to furnish high-level performance reverse-osmosis membranes, with greater osmotic-pressure bearing capacity and higher stability.

Facile photochemical synthesis of main-chain-type semifluorinated alternating copolymers catalyzed by conventional amines or halide salts

In this work, we report a much simpler and low-cost method to prepare main-chain-type semifluorinated alternating copolymers by the formation of a halogen bond (XB) complex between α,ω-diiodoperfluoroalkanes and amines/halide salts. It is interesting that the terminal iodine functional group of the polymer chains is easily lost in the amine-promoted system, while the loss can be significantly reduced by adding a small amount of water. Importantly, the system promoted by halide salts can ensure complete retention of the iodine functional group. Overall, the establishment of this method provides a new strategy for designing smart fluoropolymer materials in a green and environmentally friendly facile manner under irradiation with visible light at room temperature.

Strong synergistic effect of cationic hydrocarbon surfactant and novel nonionic tri-block short-chain fluorocarbon surfactant mixtures on surface activity, wettability and solubilization

Abstract

Mixing hydrocarbon surfactants with fluorocarbon surfactants is still an important strategy to improve the economic benefits and performances of fluorocarbon surfactants and expand their range of application. Herein, we prepared a novel kind of hydrocarbon-fluorocarbon surfactant mixtures via mixing a cationic surfactant, cetyltrimethylammonium bromide (CTAB), with a tri-block nonionic short-chain fluorocarbon surfactant (F9EG13F9) in aqueous solution. The results showed that adding a small CTAB amount to F9EG13F9 (the molar fraction of CTAB in the mixture (x1) was 0.2) could greatly reduce its critical micelle concentrations (cmc) from 0.408 mmol/L to 0.191 mmol/L. At this x1, the contact angle of the mixture was the minimum (57.7 °) at 100 s on polytetrafluoroethylene film, which was even lower than that of F9EG13F9. Besides, CTAB/F9EG13F9 mixtures possessed better colloidal stability and solubilization ability toward hydrophobic dye (Sudan І) than F9EG13F9. The outstanding performances of binary surfactant mixtures benefited from the non-ideal mixing and strong synergistic effect evidence that CTAB/F9EG13F9 surfactant mixtures could be used in practical applications instead of individual F9EG13F9, thereby reducing the used cost of F9EG13F9.

Graphical abstract

Synthesis and application of non-bioaccumulable fluorinated surfactants: a review

Abstract

Due to negative effects of conventional fluorinated surfactants with long perfluorocarbon chain (CxF2x+ 1, x≥7) like perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), these conventional long perfluorocarbon chain surfactants have been restricted in many industrial applications. Nowadays, their potential non-bioaccumulable alternatives have been developed to meet the requirements of environmental sustainable development. In this paper, the recent advances of potential non-bioaccumulable fluorinated surfactants with different fluorocarbon chain structures, including the short perfluorocarbon chain, the branched fluorocarbon chain, and the fluorocarbon chain with weak points, are reviewed from the aspects of synthesis processes, properties, and structure-activity relationships. And their applications in emulsion polymerization of fluorinated olefins, handling membrane proteins, and leather manufacture also are summarized. Furthermore, the challenges embedded in the current non-bioaccumulable fluorinated surfactants are also highlighted and discussed with the hope to provide a valuable reference for the prosperous development of fluorinated surfactants.

Graphical abstract

Synthesis of size-controlled and highly monodispersed silica nanoparticles using a short alkyl-chain fluorinated surfactant

Highly monodispersed silica nanoparticles (SiNPs) were synthesised using a fluorinated surfactant, HOCH2CH(CF3)CO2H, and its efficiency was compared with efficiencies of five other surfactants. The size of the SiNPs (∼50-200 nm) was controlled by controlling the surfactant amount. The short alkyl-chain fluoro surfactant was found to be more efficient at producing monodispersed SiNPs than its long alkyl-chain fluoro or non-fluorinated surfactant counterparts.

The high persistence of PFAS is sufficient for their management as a chemical class

Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic organic substances with diverse structures, properties, uses, bioaccumulation potentials and toxicities. Despite this high diversity, all PFAS are alike in that they contain perfluoroalkyl moieties that are extremely resistant to environmental and metabolic degradation. The vast majority of PFAS are therefore either non-degradable or transform ultimately into stable terminal transformation products (which are still PFAS). Under the European chemicals regulation this classifies PFAS as very persistent substances (vP). We argue that this high persistence is sufficient concern for their management as a chemical class, and for all "non-essential" uses of PFAS to be phased out. The continual release of highly persistent PFAS will result in increasing concentrations and increasing probabilities of the occurrence of known and unknown effects. Once adverse effects are identified, the exposure and associated effects will not be easily reversible. Reversing PFAS contamination will be technically challenging, energy intensive, and costly for society, as is evident in the efforts to remove PFAS from contaminated land and drinking water sources.

F--Free Deoxyhydrotrifluoromethylation of α-Keto Esters with Ph3P+CF2CO2-: Synthesis of α-CF3-Substituted Esters

Trifluoromethylated compounds are usually obtained via trifluoromethylation reaction by the use of CF₃SiMe₃ and NaSO₂CF₃, Umemoto's and Togni's reagents. Here, an external fluorine anion-free direct deoxyhydrotrifluoromethylation of α-keto esters with a difluoromethylating reagent has been achieved, in which the employment of water can promote the dissociation of the CF₂ group to form a CF₃ moiety, which provides the successful transformation. The current protocol demonstrates one of the most practical approaches to generate α-trifluoromethyl esters with a broad substrate scope and high functional group compatibility, in which it is applicable to late-stage modification of biologically active compounds and can be readily scaled up. Mechanistic investigation reveals that an in situ-generated gem-difluoroalkene intermediate is decomposed by water, giving rise to acid fluoride and HF.

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.

Emulsion copolymerization of vinylidene fluoride (VDF) with perfluoromethyl vinyl ether (PMVE)

The radical emulsion copolymerization of vinylidene fluoride (VDF) with perfluoromethyl vinyl ether (PMVE), initiated by potassium persulfate in the presence or absence of a surfactant is presented.

Fluoropolymers: The Right Material for the Right Applications

An overview on the synthesis, properties, and applications of fluoropolymers (PFs) is presented. First, a non-exhaustive summary on the homopolymers from conventional radical polymerization of fluoromonomers is proposed. FPs are interesting materials thanks to their outstanding properties such as thermal, oxidative and chemical resistances, low dissipation factor, refractive index, permittivity, and water absorptivity, as well as excellent durability and weatherability. Various strategies of synthesis are proposed, especially on recent studies on radical (co)polymerization of fluoroalkenes, just like their properties and applications ranging from coatings and energy-related materials (e.g. fuel cell membranes, components for lithium ion batteries, electroactive devices, and photovoltaics) to original fluorinated elastomers, surfactants, thermoplastic elastomers, thermostables, and optical devices.

Poly(meth)acrylate-PVDF core–shell particles from emulsion polymerization: preferential formation of the PVDF β crystal phase

PVDF-poly(methacrylate) core–shell particles prepared via emulsion polymerization preferentially show β phase PVDF crystallinity.