Perfluorohexyl Ethyl Acrylate Research Articles

Thermoresponsive Reversible Unimer Micelles of Amphiphilic Fluorinated Copolymers

AbstractAmphiphilic fluorinated copolymers PEGMAx‐co‐FAy and TEGMAx‐co‐FAy are prepared by activators regenerated by electron transfer atom transfer radical polymerization (ARGET‐ATRP). All polymers present a reversible thermoresponsive lower critical solution temperature‐type behavior, and a cloud point temperature (Tc) in the range of 30–60 °C strictly dependent on the length of the oxyethylene side chain, the content of the hydrophobic counits, and the concentration of the solution. Combined small angle X‐ray scattering (SAXS) and dynamic light scattering measurements are used to study the self‐assembly behavior in water, organic solvents (tetrahydrofuran [THF] and dimethylformamide [DMF]), and a fluorinated solvent (hexafluorobenzene [HFB]). SAXS confirms the formation of compact‐globular single‐chain self‐folded unimer micelles in water below Tc, which generally presents small hydrodynamic diameters (Dh ≤ 8 nm) as a result of the folding of the hydrophobic perfluorohexylethyl acrylate counits. The copolymers are also able to form reverse unimer micelle in HFB. The copolymers are not able to self‐assemble in unimer micelles in THF or DMF solutions, in which they adopt conventional random coil conformations.

Self-Assembled Amphiphilic Fluorinated Random Copolymers for the Encapsulation and Release of the Hydrophobic Combretastatin A-4 Drug.

Water-soluble amphiphilic random copolymers composed of tri(ethylene glycol) methacrylate (TEGMA) or poly(ethylene glycol) methyl ether methacrylate (PEGMA) and perfluorohexylethyl acrylate (FA) were synthesized by ARGET-ATRP, and their self-assembling and thermoresponsive behavior in water was studied by dynamic light scattering (DLS) and UV-vis spectroscopy. The copolymer ability to self-fold in single-chain nano-sized structures (unimer micelles) in aqueous solutions was exploited to encapsulate Combretastatin A-4 (CA-4), which is a very hydrophobic anticancer drug. The cloud point temperature (Tcp) was found to linearly decrease with increasing drug concentration in the drug/copolymer system. Moreover, while CA-4 was preferentially incorporated into the unimer micelles of TEGMA-ran-FA, the drug was found to induce multi-chain, submicro-sized aggregation of PEGMA-ran-FA. Anyway, the encapsulation efficiency was very high (≥81%) for both copolymers. The drug release was evaluated in PBS aqueous solutions both below and above Tcp for TEGMA-ran-FA copolymer and below Tcp, but at two different drug loadings, for PEGMA-ran-FA copolymer. In any case, the release kinetics presented similar profiles, characterized by linear trends up to ≈10–13 h and ≈7 h for TEGMA-ran-FA and PEGMA-ran-FA, respectively. Then, the release rate decreased, reaching a plateau. The release from TEGMA-ran-FA was moderately faster above Tcp than below Tcp, suggesting that copolymer thermoresponsiveness increased the release rate, which occurred anyway by diffusion below Tcp. Cytotoxicity tests were carried out on copolymer solutions in a wide concentration range (5–60 mg/mL) at 37 °C by using Balb/3T3 clone A31 cells. Interestingly, it was found that the concentration-dependent micro-sized aggregation of the amphiphilic random copolymers above Tcp caused a sort of “cellular asphyxiation” with a loss of cell viability clearly visible for TEGMA-ran-FA solutions (Tcp below 37 °C) with higher copolymer concentrations. On the other hand, cells in contact with the analogous PEGMA-ran-FA (Tcp above 37 °C) presented a very good viability (≥75%) with respect to the control at any given concentration.

Click preparation and mechanism on amphiphilic oleophobic/hydrophilic behavior of fluorinated diblock copolymers

AbstractIn this article, amphiphilic fluorinated diblock copolymers of poly(perfluorohexylethyl acrylate)‐block‐allylpolyethyleneglycol (PF6A‐b‐APEG1200) are synthesized by reversible addition‐fragmentation transfer (RAFT) polymerization and sequential thiol‐ene click reaction. The molecular structure is characterized by 1H nuclear magnetic resonance (1H NMR) spectra and Fourier transform infrared (FTIR) spectra. Morphology and particle size of resultant copolymer micelles in aqueous solution are analyzed by transmission electron microscope (TEM) and dynamic light scattering (DLS). The wettability and relative element contents of PF6A‐b‐APEG1200 coatings are investigated with contact angle (CA) and X‐ray photoelectron spectroscopy (XPS). When PF6A‐b‐APEG1200 coating is stimulated by water, the fluorine content at the top fluoropolymer‐air interface decreases and the water contact angle of the surface decreases over time, showing the hydrophilicity. While stimulated by n‐hexadecane, the fluorine content of the film surface increases, showing the oleophobicity with a stable apparent oil contact angle of 72 ± 1°. According to the detailed analysis of XPS results, the stimuli‐responsive behavior of the amphiphilic polymers can be ascribed to the migration and rearrangement of the two blocks in PF6A‐b‐APEG1200, which might probably be one of the universally accepted oleophobic/hydrophilic mechanisms.

Waterborne butyl methacrylate (co)polymers prepared by pickering emulsion polymerization: Insight of their use as coating materials for slow release-fertilizers

A new approach for preparing slow-release membranes encapsulated diammonium phosphate (DAP) fertilizer with waterborne polymers is presented. Latex dispersions based on butyl methacrylate (BMA) and 2-(perfluorohexyl)ethyl acrylate (PFA) were successfully synthesized by emulsion (co)polymerization using starch nanocrystals (SNC) as a sole pickering surfactant. A conversion degree around 98% was reached, while the solid content was close to 20 wt%. The particle diameter distribution of PBMA homopolymer and P(BMA-co-PFA) copolymer dispersions as well as the water contact angle measurements and thermal properties were investigated and showed that the incorporation of PFA units in PBMA enhanced the thermal stability and the hydrophobic character of the copolymer. The use of these (co)polymers as fertilizer coatings was explored. Scanning Electronic Microscopy (SEM), Electronic Diffraction X-ray (EDX) and mapping were performed to study the morphology of the coated fertilizer granules and revealed the formation of a cohesive film with a good adhesion between DAP fertilizer and coating films. The evaluation of the release of nutrients (N, P) was monitored by UV–Vis spectroscopy. Compared to uncoated DAP granules which the total release was obtained after less than 2 h, the P release profiles of the coated fertilizers reached the equilibrium stage after 28 and 50 h when the DAP was coated with PBMA and P(BMA-co-FPA), respectively. Indeed, the time to reach the maximum N release concentration was 13.5 and 16.0 times lower than the corresponding uncoated DAP when the DAP was covered with PBMA and P(BMA-co-FPA), respectively. These results indicated significant slower nutrients (P and N) release properties to enhance the efficiency of fertilizer use and minimize adverse environmental effects, and to match with the nutrient demand during crop growth.

Robust fluorinated siloxane copolymers via initiated chemical vapor deposition for corrosion protection

Homopolymers of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4), 2-(perfluorohexyl)ethyl acrylate (PFHEA) and 2-(perfluoroalkyl)ethyl methacrylate (PFEMA) and their copolymers were synthesized via initiated chemical vapor deposition (iCVD). All coatings exhibited excellent adhesion to substrates. The corrosion resistance of iCVD coatings was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. In addition, chemical durability of various organic solvents and adhesion to the substrate were also evaluated. Tafel polarization measurements in 5 wt% NaCl solution revealed that the corrosion rates as low as 0.002 mpy on zinc substrates can be reached with 250-nm-thick iCVD-synthesized polymers which is lower than previously reported polymer coatings and more than three orders of magnitude lower than bare zinc. EIS analysis coupled with equivalent electric circuits model confirmed that poly(V4D4) and poly(PFHEA) homopolymers show extremely high protection efficiencies (~ 99%) on zinc, while poly(V4D4-co-PFHEA) copolymer with slightly lower corrosion efficiency (85–91%) provides a better anticorrosion barrier with weight loss reduction by 57 and 45% for copper and zinc, respectively, and with improved chemical and mechanical properties. The results indicate that iCVD process enables fabrication of finely tuned fluorinated siloxane copolymer conformal coatings for corrosion protection on a variety of substrates.

Synthesis and performances of 9,9‐bis(perfluorohexylethyl propionate) fluorene copolymers

Abstract2,7‐dibromo‐9,9‐bis(perfluorohexylethyl propionate) fluorene was synthesized by Michael addition reaction using 2,7‐dibromofluorene and perfluorohexyl ethyl acrylate as the reactants. 9,9‐Bis(perfluorohexylethyl propionate) fluorene copolymers were then synthesized by Suzuki coupling reaction with 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborane‐diyl)‐9,9 ‐dioctyl fluorene, 2,7‐dibromo‐9,9‐dioctyl fluorene and 2,7‐dibromo‐9,9‐bis(perfluorohexylethyl propionate) fluorene as the monomers. The fluorinated fluorene copolymers were characterized and investigated via Fourier infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy (1HNMR), ultraviolet absorption spectroscopy (UV–vis), cyclic voltammetry (CV) and photoluminance spectroscopy (PL). Because of the long fluorine‐containing alkyl side chain, the ultraviolet absorption peak of 9,9‐bis(perfluorohexylethyl propionate) fluorene is blue‐shifted compared with poly(9,9‐dioctylfluorene)(PF8). The LUMO energy level increases and the energy band gap of copolymers widens. Due to the self‐assembly of the long fluoroalkyl side chain, the photoluminance spectra of 9,9‐bis(perfluorohexylethyl propionate) fluorene copolymers exhibit a new excimer emission peak at 550 nm. The photoluminance stabilities of the copolymers under irradiation and humid conditions are significantly improved due to protective effect from the long fluoroalkyl side chain. After being irradiated under 500 W iodine tungsten lamp or kept under 70% relative humid conditions, the 9,9‐bis(perfluorohexylethyl propionate) fluorene copolymers showed much better photoluminance stability than that of poly(9,9‐dioctylfluorene) (PF8). These show that introducing long fluoroalkyl side chain into conjugated polymer main chain is a promising strategy to improve environmental stability of devices based on organic conjugated polymers.

Solvent-free fabrication of tough self-crosslinkable short-fluorinated copolymer nanocoatings for ultradurable superhydrophobic fabrics

• Tough short-fluorinated nanocoatings were fabricated by solvent-free iCVD. • Isocyanate chemistry induced self-crosslinking and fixated surface fluorinated chains. • Self-crosslinking enabled excellent dynamic water repellency and mechanical strength. • Conformal nanocoating imparted fabrics ultradurable superhydrophobicity. As long-perfluorinated side chain polymers are phasing out due to healthy and environmental concerns, short-fluorinated polymers are garnering increasing attention as a substitute for superhydrophobic coatings. Challenges, however, are to be addressed due to the poor dynamic water repellency and unsatisfactory durability of short-fluorinated polymer coatings. This work reports the fabrication of self-crosslinkable poly(perfluorohexylethyl acrylate- co -isocyanato ethyl methacrylate) nanocoating with good dynamic water repellency and high mechanical strength using a solvent-free initiated chemical vapor deposition (iCVD) method. The employment of highly reactive isocyanate groups in the coating not only facilitated covalent binding with functional groups on the substrate surface, but also enabled self-crosslinking reactions in the presence of water vapor. Crosslinking immobilized the fluorinated chains on the surface, thus alleviating the contact angle hysteresis. The crosslinked network also significantly improved the mechanical strength of the coating. Without affecting fabric morphology, the coating enabled superhydrophobicity of different fabrics with water sliding angle as low as 3˚. Such superhydrophobicity was well maintained after various harsh durability tests, including sandpaper abrasion for up to 20,000 cm, ultrasonication and boiling for more than 12 h, etc. The achieved durability was attributed to the enhanced adhesion strength and excellent mechanical property of the coating. This work thus paves a novel way towards eco-friendly fabrication of durable superhydrophobic fabrics.

Molecular Dynamics of Amphiphilic Random Copolymers in the Bulk: A 1H and 19F NMR Relaxometry Study

AbstractA set of amphiphilic random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and perfluorohexylethyl acrylate (FA) with different compositions synthesized by atom transfer radical polymerization (ATRP) is investigated by 1H and 19F NMR relaxometry. In particular, a thorough investigation of T1 and T2 relaxation times at variable temperature and copolymer composition provides the first complete and detailed characterization of the dynamics of both the main chain backbone and the side chains of the PEGMA‐co‐FA copolymers. The results highlight an intramolecular segregation of rigid main chain and mobile side chains, and an additional self‐assembling of the PEGMA and FA side chains into distinct nanodomains, driven by the hydrophobic interactions between FA side chains. The obtainment and observation of nanoscale phase separation in random copolymers is a promising achievement to the aim of controlling self‐assembly in the bulk by suitably modulating copolymers composition, which can open novel avenues to easier fabrications and applications in nanotechnologies.

Single-chain self-folding in an amphiphilic copolymer: An integrated experimental and computational study

An amphiphilic random copolymer of hydrophilic poly(ethylene glycol) methyl ether methacrylate with hydrophobic perfluorohexylethyl acrylate, PEGMA77-co-FA23, was synthesized by ATRP and used to investigate self-assembling into nanostructures in water and chloroform solutions, both experimentally and computationally. The dynamic light scattering measurements on water solutions of the copolymer at room temperature evidenced the presence of nanoassemblies with hydrodynamic diameter Dh = 4 ± 1 nm. The behavior of fluorescence emission intensity of water solutions with added ethidium bromide suggested confinement of the molecular rotor within a hydrophobic environment of the copolymer. Moreover, these nanoassemblies were thermoresponsive and reversibly collapsed into much larger, multi-chain aggregates with Dh = 390 ± 20 nm at a critical temperature of 55 °C (5 mg mL−1). Molecular dynamics simulations revealed the formation of single-chain, prolate globular nanoassemblies with a structural variability in water solution at room temperature. The evolutions of the simulated radius of gyration (Rg), asphericity, prolateness and solvent-accessible surface area were analyzed along the folding trajectories. Thus, self-folding appeared to result from the interplay between hydrophobic interactions and structural constraints which leads to rather complex nanostructures (Rg = 20–25 Å, 200 ns simulation). By contrast, folding in much more open polymer conformations (Rg = 30–40 Å) was predicted for chloroform solutions.

The self‐assembly over nano‐ to submicro‐length scales in water of a fluorescent julolidine‐labeled amphiphilic random terpolymer

ABSTRACTA novel fluorescent‐labeled amphiphilic random terpolymer is synthesized by controlled radical polymerization of a fluorescent molecular rotor monomer, 2‐cyano‐2‐[4‐vinyl(1,1′‐biphenyl)‐4′‐yl]vinyljulolidine, a hydrophilic monomer, poly (ethylene glycol) methyl ether methacrylate, and a hydrophobic monomer, perfluorohexylethyl acrylate. Combined dynamic light scattering and fluorescence emission spectroscopy measurements are used to investigate its self‐assembly in water solution. Self‐assembled nanostructures with a hydrodynamic diameter size Dh of 4 ± 1 nm are detected due to the single‐chain folding of the terpolymer in unimer micelles. The fluorescence emission intensity of the terpolymer in water solution is found to be one order of magnitude higher than that in organic solvents, as a result of the preferential encapsulation of the julolidine co‐units in hydrophobic compartments of the unimer micelles. The temperature dependence of the self‐associative behavior of the amphiphilic terpolymer is also investigated and a critical temperature is identified at which a transition between single‐chain unimer micelles and multi‐chain aggregates (Dh = 400 ± 40 nm) reversibly takes place on heating–cooling cycles. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 797–804

Synthesis of sulfonyl fluorinated macro emulsifier for low surface energy emulsion polymerization application

ABSTRACTFluorinated acrylate emulsions have been extensively applied for hydrophobic surface coatings. To obtain fluorinated emulsions of low surface energy, amphiphilic sulfonyl macro emulsifiers consisting of 2‐(perfluorohexyl) ethyl acrylate (PFHEA) and 2‐acrylanmido‐2‐methylpropanesulfonic acid (AMPS) were designed via radical polymerization and subsequently used for the emulsion copolymerization of PFHEA, methyl methacrylate (MMA), and methyl butyl acrylate (MBA). Under optimum synthesis conditions, the emulsifier displayed superior emulsification properties such as high monomer conversion, small particle size, and excellent stability compared with conventional emulsifiers. The corresponding emulsions with sulfonyl macro emulsifiers exhibited extreme low surface energy (9.8 mN/m) and outstanding hydrophobicity due to high contents of fluorinated chains, as well as thimbleful hydrophilic sulfonyl groups, which shows the great potential in water repellent modification application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44921.

Synthesis, characterization, and property of amphiphilic fluorinated abc-type triblock copolymers

Novel amphiphilic fluorinated ABC-type triblock copolymers composed of hydrophilic poly(ethylene oxide) monomethyl ether (MeOPEO), hydrophobic polystyrene (PSt), and hydrophobic/lipophobic poly(perfluorohexylethyl acrylate) (PFHEA) were synthesized by atom transfer radical polymerization (ATRP) using N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/CuBr as a catalyst system. The bromide-terminated diblock copolymers poly(ethylene oxide)-block-polystyrene (MeOPEO-b-PSt-Br) were prepared by the ATRP of styrene initiated with the macroinitiator MeOPEO-Br, which was obtained by the esterification of poly(ethylene oxide) monomethyl ether (MeOPEO) with 2-bromoisobutyryl bromide. A fluorinated block of poly(perfluorohexylethyl acrylate) (PFHEA) was then introduced into the diblock copolymer by a second ATRP process to synthesize a novel ABC-type triblock copolymer, poly(ethylene oxide)-block-polystyrene-block-poly(perfluorohexylethyl acrylate) (MeOPEO-b-PSt-b-PFHEA). These block copolymers were characterized by means of proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). Water contact angle measurements revealed that the polymeric coating of the triblock copolymer (MeOPEO-b-PSt-b-PFHEA) shows more hydrophobic than that of the corresponding diblock copolymer (MeOPEO-b-PSt). Bovine serum albumin (BSA) was used as a model protein to evaluate the protein adsorption property and the triblock copolymer coating posseses excellent protein-resistant character prior to the corresponding diblock copolymer and polydimethylsiloxane. These amphiphilic fluoropolymers can expect to have potential applications for antifouling coatings and antifouling membranes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis and Characterization of Novel Amphiphilic Fluorinated Triblock Copolymer

Atom transfer radical polymerization (ATRP) has been employed for the synthesis of a novel amphiphilic fluorinated triblock copolymer PEG-b-PS-b-PFHEM for anti-fouling coatings. The macroinitiator based on poly(ethylene oxide) monomethyl ether was used to prepare an amphiphilic diblock copolymer PEG-b-PSt-Br, which was then utilized to initiate the ATRP of fluorinated monomer perfluorohexylethyl acrylate (FHEA), resulting in an amphiphilic triblock copolymer. These copolymers were characterized by means of 1H NMR and GPC. The amphiphilic triblock copolymer surface composes of fluorinated and PEGylated blocks, and the fluorinated surface has critical surface energy, while the PEGylated surface is expected to have a relatively low interfacial energy when in contact with water. Microphase-separation of both blocks could take place and result in the reduction of protein adsorption and cell adhesion. The amphiphilic fluoropolymer has the potential application as excellent antifouling coatings and antifouling membranes.

Application of Fluorinated Alkyl Acrylate to Denture Base Resin Influence of Carbon Chain Length of Fluorinated Alkyl Acrylate on Bacterial Adherence

This study examined the influence of carbon chain length of fluorinated alkyl acrylate on bacterial adhesion to the surface of test specimens. Perfluorobutylethyl acrylate (C4F), perfluorohexylethyl acrylate (C6F), perfluorooctylethyl acrylate (C8F), and perfluorodecylethyl acrylate (C10F) were used as fluorinated alkyl acrylate monomers. All specimens with the fluoro-monomer added exhibited significantly higher water-shedding and oil-shedding surface characteristics when compared to control (MMA/PMMA). Furthermore, contact angle for droplets of water and dodecane on the fluoromonomer-added specimens increased with carbon chain length of the perfluoroalkyl groups. Bacterial adhesion was significantly suppressed on the fluoromonomer-added specimens, both the saliva-uncoated and -coated specimens. In addition, the number of Candida albicans adhering to both the saliva-uncoated and -coated fluoromonomer-added specimens decreased with an increase in perfluoroalkyl carbon chain length. The results suggest that the application of fluorinated alkyl acrylate to denture base resin can modify the surface characteristics, and that fluorinated alkyl acrylate with long carbon chains of C8F and C10F successfully inhibit bacterial adherence to the resin surface.

Influence of Carbon Chain Length of Fluorinated Alkyl Acrylate on Mechanical Properties of Denture Base Resin

Hayashi et al. recently succeeded in preparing a filling polymer composed of methyl methacrylate and perfluorooctylethyl acrylate (C8F). They suggested that the addition of C8F-added polymer beads could inhibit bacterial adherence to the surface of denture base resin. The objective of this study was to examine the influence of carbon chain length of fluorinated alkyl acrylate on mechanical properties of test specimens ; perfluorobutylethyl acrylate (C4F), perfluorohexylethyl acrylate (C6F), C8F and perfluorodecylethyl acrylate (C10F) were used as fluorinated alkyl acrylates. The glass transition temperature of test specimens appeared to be greater as carbon chain length of fluorinated alkyl acrylate increased. Knoop hardness was lowest in C6F-added specimens (C6FA), while all test specimens gave lower values than the control. The direct tensile strengths of fluoromonomer-added specimens were lower than the control, while relatively lower strengths were seen in C6FA or C8F-added specimens (C8FA). Although Knoop hardness and direct tensile strength decreased after addition of fluorinated alkyl acrylates, these mechanical properties remained within the limits recommended by the Japanese Society for Dental Materials and Devices for denture base resin. This study suggests that the new denture base resin is clinically acceptable with regard to mechanical properties.