Fluorinated comblike homopolymers: The effect of spacer lengths on surface properties

A series of polyacrylate monomers with F‐alkylalkyl [F(CF₂)_n(CH₂)_n′] side groups were prepared by free‐radical polymerization. The effect of the chemical structure on the surface properties of poly(ethylene terephthalate)s was evaluated by variations in the relative length of the fluorocarbon and hydrocarbon units in the side group. The resulting polymers were quite surface‐active in the solid state. The surface and bulk organization was investigated by X‐ray photoelectron spectroscopy analysis. A strong correlation between the bulk organization and surface properties of the polymers was established. The outmost layer, formed from trifluoromethyl groups and some ester functions, suggests that the side chain is arranged irregularly in the polymer–air interface. The length of the lateral chain governs this organization: long fluorinated chains and short hydrocarbon spacers are essential elements of the molecular design for such low‐surface‐energy materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3737–3747, 2005     

Synthesis and polymerization of novel fluorinated acrylates and methacrylates bearing alkoxyl groups derived from radical addition reaction of perfluoroisopropenyl ester

Radical addition of 2-benzoxypentafluoropropene [CF₂C(CF₃)OCOC₆H₅] (BPFP) with alcohols such as ethanol and 2-propanol was investigated to afford fluorinated alcohols. Radical addition of BPFP with cyclic ethers such as tetrahydrofuran, 1,3-dioxolane and tetrahydropyran was also achieved to afford addition products followed by hydrolysis to yield fluorinated alcohols possessing cyclic structures. Novel fluoroalkyl acrylates and methacrylates were synthesized from the fluorinated alcohols with (meth)acryloyl chlorides. Radical polymerization of the fluoroalkyl (meth)acrylates yielded polymers of 1.2 × 10⁵ as the highest molecular weight.     

Glycosylidene Carbenes. Part 6. Synthesis of alkyl and fluoroalkyl glycosides

The syntheses of glycosides from the diazirine 1 and a range of alcohols under thermal and/or photolytic conditions are described. Yields and diastereoselectivities depend upon the pK_HA values of the alcohols, the solvent, and the reaction temperature. The glycosidation of weakly acidic alcohols (MeOH, EtOH, i-PrOH, and t-BuOH, 1 equiv. each) in CH₂Cl₂ at room temperature leads to the glycosides 2–5 in yields between 60 and 34% (Scheme 1 and Table 1). At ?70 to ?60°, yields are markedly higher. In CH₂Cl₂, diastereoselectivities are very low. In THF, at ?70 to ?60°, however, glycosidation of i-PrOH leads to α-D -/β-D - 4 in a ratio of 8:92. More strongly acidic alcohols, such as CF₃CH₂OH, (CF₃)₂ CHOH, and (CF₃)₂C(Me)OH, and the highly fluorinated long-chain alcohols CF₃(CF₂)₅(CH₂)₂OH ( 11 ) and CHF₂(CF₂)₉CH₂OH ( 13 ) react (CH₂Cl₂, r.t.) in yields between 73 and 85% and lead mainly to the β-D -glucosides β-D - 6 to β-D - 8 , β-D - 12 , and β-D - 14 (d.e. 14–68%). Yields and diastereoselectivities are markedly improved, when toluene, dioxane, 1,2-dimetoxyethane, or THF are used, as examined for the glycosidation of (CF₃)₂C(Me)OH, yielding (1,2-dimethoxyethane, 25°) 80% of α-D -/ β-D - 8 in a ratio of 2:98 (d.e. 96%; Table 4). In EtCN, (CF₃)₂C(Me)OH yields up to 55% of the imidate 10 . Glycosidation of di-O-isopropylideneglucose 15 leads to 16 (CH₂Cl₂, r.t.; 65%, α-D / β-D = 33:67). That glycosidation occurs by initial protonation of the intermediate glycosylidene carbene is evidenced, for strongly acidic alcohols, by the formation of 10 , derived from the attack of (CF₃)₂MeCO^? on an intermediate nitrilium ion (Scheme 4), and for weakly acidic alcohols, by the formation of α-D - 9 and β-D - 9 , derived by attack of i-PrO^? on intermediate tetrahydrofuranylium ions. A working hypothesis is presented (Scheme 3). The diastereoselectivities are rationalized on the basis of a protonation in the σ plane of the intermediate carbene, the stabilization of the thereby generated ion pair by interaction with the BnO? C(2) group, with the solvent, and/or with the alcohol, and the final nucleophilic attack by RO^? in the π plane of the (solvated) oxonium ion.     

Fluoro-olefin chemistry Part 20 [1]. Reaction of hexafluoropropene with alcohols

Reaction of hexafluoropropene (HFP) with a series of alcohols under thermal, photochemical or peroxide-initiated conditions affords the 1:1 adducts CF₃CHFCF₂CR¹R²OH (R¹ = H, R² = H, Me, Prⁿ or CF₃; R¹ = Me, R² = Me or Et) in high yield via a radical chain mechanism. Adduct are not formed with the alcohols (CF₃)₂CHOH and CF₃CHFCF₂CH₂OH. Other 1:1 adducts of structure CHF₂CF(CF₃)CH₂OH and CH₃(C₂H₃CF₂CHFCF₃)CH₂OH are formed as minor products in the methanol and $\text{n}$-butanol reactions, respectively.     

Effect of the structural parameters of a series of fluoromonoacrylates on the surface properties of cured films

A series of fluorinated acrylates [F(CF₂)_q? (CH₂)_p? OCOCH?CH₂, where q = 8 and p = 2 ÷ 11) were synthesized and used as comonomers in the photopolymerization of acrylic systems. These fluoroacrylates were synthesized in a three‐step procedure through the radical addition of perfluoroalkyliodides to an unsaturated alcohol followed by their acrylation. The mixtures, containing up to 0.8% (w/w) of the comonomers, produced transparent films after UV curing; they showed changes in the surface properties as a function of the comonomer type and concentration. With contact‐angle and X‐ray photoelectron spectroscopy analyses, the relationship between the structure of the monomers and the surface properties of the UV‐cured films was investigated: the wettability decreased, depending on the length of the fluorinated group (q value) and the hydrogenated segment of the monomer (p value). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4227–4235, 2001     

Photolysis of a fluorinated polymer film by vacuum ultraviolet radiation

We studied the photolysis of a fluoroethylene–fluoropropylene copolymer (FEP) film by vacuum ultraviolet (VUV) radiation from a resonance Xe lamp at a wavelength of 147 nm and air pressures of 0.05 and 2.5 Torr. The chemical changes in the FEP surface layer were investigated by Fourier-transform infrared spectroscopy with attenuated total reflection attachment and X-ray photoelectron spectroscopy. Double bonds were found to be the main product in the case of VUV treatment at 0.05 Torr, while photo-oxidation of FEP occurred predominantly by VUV treatment at 2.5 Torr under formation of the —CF₂C(O)F group. This oxygen-containing group was more effectively formed in the FEP surface layer by VUV photo-oxidation than by conventional surface oxidation techniques such as treatments by plasma and corona discharge and ozone. Storage of the VUV-treated polymers in air at 50% relative humidity resulted in hydrolysis of —CF₂C(O)F to the —CF₂COOH group. Substantial improvement of the film wettability was noticed after VUV photo-oxidation. These findings suggest that VUV irradiation provides a high potential for surface modification of fluorinated polymers which are known to be particularly resistant against functionalization by conventional surface modification techniques such as plasma treatment. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2215–2222, 1998     

Fluorinated vs hydrogenated surfactants in mixtures with valinomycin—The Langmuir monolayer study

Selected fluorinated and hydrogenated surfactants, namely a semifluorinated alkane (SFA): 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-henicosafluorononacosane (F10H19), two long chain alcohols: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-ol (F8H10OH) and octadecane-1-ol (C18OH) and with two long chain thiols of the analogous apolar part structure to the above-mentioned alcohols, i.e.: 18,18,18,17,17,16,16,15,15,14,14,13,13,12,12,11,11-heptadecafluorooctadecane-1-thiol (F8H10SH) and octadecane-1-thiol (C18SH) have been tested in mixtures with valinomycin as potential artificial matrixes for its immobilization. The thermodynamic analysis (ΔG^exc vs X_val plots) based on surface pressure–area isotherm registration for particular valinomycin/surfactant mixtures, complemented with BAM images of the films structure indicate that only fluorinated surfactants are suitable materials for valinomycin incorporation as they form homogeneous miscible monolayers at X_val below 0.5.     

Features of the reaction of polyfluoroalkyl chlorolsulfites with allyl alcohol

Unlike the saturated aliphatic and aromatic alcohols, allyl alcohol under the same conditions reacts with polyfluoroalkyl chlorosulfites to form not ethers, but polyfluorinated alcohols. The exception is polyfluoroalkyl chlorosulfites with the chain length of more than five carbon atoms. Allyl ethers of polyfluorinated alcohols of general formula CH₂=CHCH₂OCH₂(CF₂CF₂)nH (n = 1–3) were obtained, when the reaction proceeded in the presence of potassium carbonate, owing to its participation in a specific orientation of the reaction centers in the resulting intermediate structure, which is easily transformed into allyl ethers of polyfluorinated alcohols.     

Novel fluorinated polymers by radical polyaddition: Inspiration and progress

The story of the outset and the growth of radical polyaddition of bisperfluoroisopropenyl derivatives [CF₂?C(CF₃)? R? C(CF₃)? CF₂] with several organic compounds possessing carbon–hydrogen bonds is described. The reaction afforded novel fluorinated polymers bearing such organic segments in polymer main chains as 1,4‐dioxane, diethyl ether, dimethoxyethane, 18‐crown‐6, triethylamine, glutaraldehyde, and alkanes which have never been supposed as direct starting compounds for preparation of polymers. The facile method for preparation of fluorinated hybrid polymers bearing alkylsilyl groups was developed with diethoxydimethylsilane and silsesquioxanes. Taking advantage of the high reactivity of the perfluoroisopropenyl group as a radical acceptor, self‐polyaddition and cyclopolymerization were investigated. Triethysilyl perfluoroisopropenyl ether [CF₂? C(CF₃)? O? Si(C₂H₅)₃] was proved to be the most probable candidate for self‐polyaddition. Cyclopolymerization of perfluoroisopropenyl vinylacetate [CF₂?C(CF₃) OCO? CH₂CH? CH₂] was investigated to afford polymers possessing five‐membered‐ring units in main chains. The interconversion of the unstable fluorinated carbon radical and the stable hydrocarbon radical had an important role in the reaction. The radical addition reaction presented herein may be developed for preparation of a wide variety of novel fluorinated polymers and organic compounds possessing functional groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4101–4125, 2004     

The steric and electronic effects of aliphatic fluoroalkyl groups

Ab initio calculations were performed on 18 fluorinated and unfluorinated alcohols at the B3LYP and HF levels with the 6-311G^∗∗ basis set. Molar volumes of the alcohols were computed at each level and averaged to produce a scale of relative size. From this, various isosteric replacements of potential use in drug design were suggested: ethyl by FCH₂CH₂ or HCF₂CH₂, propyl by CF₃CH₂, isopropyl by CF₃(CH₃)CH or (FCH₂)₂CH, isobutyl or t-butyl by (CF₃)₂CH, and 3-methyl-2-butyl by CF₃(CH₃)₂C. Calculation of the charge on oxygen and the Wiberg index of the CO bond allowed an electronegativity scale to be constructed for the fluoroalkyl groups. Electronegativity decreased in the order: (CF₃)₃C>(CF₃)₂CH>C₂F₅CH₂>CF₃CH₂>CH₃(CF₃)₂C>HCF₂CH₂>CF₃(CH₃)CH>(FCH₂)₂CH>FCH₂CH₂>CF₃(CH₃)₂C. This ranking agreed with literature acid dissociation data for the alcohols studied.     

Trifluoromethylated allyl alcohols: acid-promoted reactions with arenes and unusual ‘dimerization’

An unusual ‘dimerization’ of CF₃-allyl alcohols [ArCHCHCH(OH)CF₃] under the action of anhydrous FeCl₃ was found to give fluorinated indanes in 62–90% yields via the formation of intermediate allyl cations. Reactions of CF₃-allyl alcohols with arenes (Ar′H) led to CF₃-alkenes [Ar(Ar′)CHCHCHCF₃] in 48–75% yields. The mechanisms of the transformations are discussed.     

Ab initio quantum-mechanical calculations on trifluoromethylamine

Extensive ab initio molecular-orbital calculations were carried out on trifluoromethylamine (TFM) to elucidate changes in geometry and electronic structure upon fluorination. The calculations show that the decomposition of CF₃NH₂ is slightly endoenergetic, and the heats of atomization of CF₃NH₂ and CH₃NH₂ show decreased stability of the species upon fluorination. Characteristic of CF₃NH₂ is a highly polar, strong, short CN bond. More limited calculations were carried out on CF₃OH and CH₃OH, and the electronic structure of CF₃OH is found to be generally similar to that of CF₃NH₂. The reduced basicity of the fluorinated amine cannot be ascribed to the inductive effect; the enhanced acidity of the fluorinated alcohol reflects the weakening of the OH bond. No evidence leads to a confirmation of the existence of nitrogen–fluorine hyperconjugation in the fluorinated amine.     

Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short‐chain alcohols

Styrene microemulsion polymerizations with different short‐chain alcohols [n‐C_iH_2i+1OH (C_iOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50–70 °C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C₆OH > C₄OH > C₅OH. This was related to the differences in the water solubility of C_iOH and the structure of the oil–water interface. The feasibility of using a water‐insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (C_iOH), the SPS concentration, and the initiator type (oil‐soluble 2,2′‐azobisisobutyronitrile versus water‐soluble SPS). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199–3210, 2001     

Synthesis of fluorinated oligomers for supercritical carbon dioxide applications

Syntheses of various fluorine‐based surfactants, namely fluorinated‐segment‐containing block co‐oligomers, were achieved by the radical polymerization of mainly acrylate‐based monomers. These types of surfactants serve as stabilizers for supercritical carbon dioxide (scCO₂) media based applications, for which the effective solubilization of materials in the supercritical phase is generally not possible because of solubility problems faced when CO₂ is involved. Initially, a difunctional fluorinated initiator was synthesized in two steps. First, 4,4′‐azobis‐4‐cyanovaleric acid was chlorinated with SOCl₂, and then the product, 4,4′‐azobis‐4‐cyanovaleryl chloride, was reacted with a fluorinated alcohol to obtain the initiator for the polymerization reactions. The synthesized triblock co‐oligomers consisted of fluorinated side blocks and a hydrocarbon intermediate block. Efficient solubilization of the materials in scCO₂ was observed. It was experimentally shown that the solubility efficiency was affected by specific interactions between CO₂ and the oligomers, and these were determined by the nature and size of the inner block and by the chain length of the fluorinated side blocks in comparison with the inner block. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5312–5322, 2005     

Synthesis and Properties of CF3(OCF3)CH‐Substituted Arenes and Alkenes†

A silver‐mediated oxidative trifluoromethylation of easily accessible α‐trifluoromethyl alcohols with TMSCF₃ was developed to access novel CF₃(OCF₃)CH‐containing compounds. Deprotonation of CF₃(OCF₃)CH‐substituted arenes afforded synthetically useful CF₃O‐substituted gem‐difluoroalkenes. Furthermore, evaluation of the lipophilicities (log P) indicated that CH(OCF₃)CF₃ is more lipophilic than the common fluorinated motifs such as CF₃, OCF₃, and SCF₃, thus rendering the CH(OCF₃)CF₃ motif appealing in drug discovery.     

New fluorinated acrylic monomers for the surface modification of UV‐curable systems

New fluorinated acrylates were synthesized and used as modifying additives for acrylic UV‐curable systems. Their chemical structure is: C_nF_2n+1 R—OCO—CHCH₂, where the linear perfluorinated chain contains from 4 to 10 carbon atoms, while R is a linear alkyl group containing or not a thioether group. Notwithstanding their very low concentration, the fluorinated monomers caused a dramatic change of the surface properties of the films, without changing their curing conditions and their bulk properties. X‐ray photoelectron spectroscopy measurements showed that the monomers were able to concentrate selectively on the surfaces of the films, depending on their chemical structure and on the kind of substrate employed. The synthesis of the fluorinated monomers and the relationship between their chemical structure and the final surface properties of the UV‐cured films will be discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 77–87, 1999     

Synthesis of fluorinated difunctional monomers

In order to obtain fluorinated difunctional monomers for fluoropolyurethanes, we synthesized novel fluorinated aliphatic diisocyanates [OCNCH₂(CF_c2)_nCH₂NCO] from corresponding diols [HOCH₂CH₂(CF₂)_nCH₂CH₂OH]. Oxidation of the diols with chromium trioxide-sulfuric acid gave α, α, ω, ω-tetrahydroperfluoroalkylene dicarboxylic acids in high yields. Then treating the acids with phosphorus pentachloride afforded corresponding dicarboxyl chlorides, which are easily converted to dicarboxyl azides with hydrazoic acid-pyridine complex. Finally, on Curtius rearangement of the azides, the end products, α, α, ω, ω-tetrahydroperfluoroalkylene diisocyanates were obtained in 53% (n=4) and 19% (n=6) yields from the starting diols.     

Synthesis of new fluorinated allyl ethers for the surface modification of thiol–ene ultraviolet‐curable formulations

Thiol–ene photocurable systems based on a trifunctional thiol [trimethylolpropane tris‐(3‐mercaptopropanoate)] and two different multifunctional allyl ethers (trimethylolpropane triallyl ether and Boltorn U2, an allyl functional dendritic polyester) were examined. To these systems, small amounts (<1 wt %) of fluorinated allyl ethers were added for the modification of their surface properties. Two new fluorinated allyl ethers, 1H,1H‐perfluoro‐1‐heptylallyl ether and 1H,1H‐perfluoro‐1‐decylallyl ether, were synthesized for this purpose by allylation of the corresponding 1H,1H‐perfluoro alcohols. The fluorinated monomers, despite their very low concentrations, caused sharp changes in the surface properties of the films and in the solvent resistance without any changes in the curing conditions and bulk properties. Completely hydrophobic surfaces were obtained (as a result of the selective enrichment of the fluorinated monomers on the film surfaces) that depended on the monomer structure and its concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2583–2590, 2002     

Original fluorinated surfactants potentially non-bioaccumulable

This minireview updates non-exhaustive recent strategies of synthesis of original fluorosurfactants potentially non-bioaccumulable. Various strategies have been focused on (i) the preparation of CF₃–X–(CH₂)_n–SO₃Na (with X = O, C₆H₄O or N(CF₃) and n = 8–12), (ii) the oligomerization of hexafluoropropylene oxide (HFPO) to further synthesize oligo(HFPO)–CF(CF₃)CO–R_H (where R_H stands for an hydrophilic chain); (iii) the telomerization of vinylidene fluoride (VDF) with 1-iodopentafluoroethane or 1-iodononafluorobutane to produce C_nF_2n+1–(VDF)₂–CH₂CO₂R (n = 2 or 4, R = H or NH₄), (iv) the radical telomerization of 3,3,3-trifluoropropene (TFP) with isoperfluoropropyliodide or diethyl hydrogenophosphonate to prepare (CF₃)₂CF(TFP)_x–R_H or CF₃–CH₂–CH₂–(TFP)_y–P(O)(OH)₂, and (v) the radical cotelomerization of VDF and TFP, or their controlled radical copolymerization in the presence of (CF₃)₂CFI or a fluorinated xanthate. In most cases, the surface tensions versus the surfactant concentrations have been assessed. These above strategies led to various highly fluorinated (but yet not perfluorinated) telomers whose chemical changes enabled to obtain original surfactants as novel alternatives to perfluorooctanoic acid (PFOA), ammonium perfluorooctanoate (APFO), or perfluorooctylsulfonic acid (PFOS) regarded as bioaccumulable, persistent, and toxic.     

1:2‐sequence‐regulated radical copolymerization of naturally occurring terpenes with maleimide derivatives in fluorinated alcohol

Naturally occurring bulky terpenes, such as (+)‐ and (–)‐limonene and (–)‐β‐pinene, were quantitatively copolymerized with maleimide (MI) derivatives (i.e., phenyl‐, cyclohexyl‐, ethyl‐, and unsubstituted‐MI) in PhC(CF₃)₂OH solvent via selective 1:2‐alternating propagation governed by the penultimate effect, which resulted in 1:2‐sequence regulated polymers with relatively high glass transition temperatures and optical activities. Similar petroleum‐derived bulky olefins possessing cyclohexenyl, cyclohexyl, or additional α‐methyl substituents were copolymerized with phenylmaleimide via preferential 1:2‐alternating propagation with a slightly lower selectivity. A further decrease in the bulkiness of nonpolar olefins increased the 1:1‐alternating sequence. The copolymerization of limonene and acrylonitrile also proceeded approximately via 1:1‐alternating propagation, in which the penultimate effect was less observable. Furthermore, when methylene chloride was used instead of fluorinated alcohol for the copolymerization of limonene and phenylmaleimide, the length of the sequence of MI units increased. Thus, in addition to the characteristic MI skeleton, the bulky and rather specific structure of either limonene or β‐pinene induces 1:2‐selective propagation via the penultimate effect, whereas the fluoroalcohol diminishes the homopropagation of MI via a hydrogen bonding interaction with the MI unit. RAFT copolymerization of limonene and various MI derivatives in PhC(CF₃)₂OH successfully proceeded to give the end‐to‐end 1:2‐sequence‐regulated copolymer with a selective initiating sequence and predominant capping sequence using an appropriate RAFT agent. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013