Fluorinated Alkyl Side Chains Research Articles

Strong Hydrophobic and Ultraviolet Reflective Film from Fluorinated Polyisoprene with Microphase Separation via Thiol–Epoxy Click Chemistry

AbstractPolyisoprene is widely used in the industrial production of tires, thermoplastic elastomers, pressure sensitive adhesives, coatings, plasticizers, lubricants, and other functional materials. However, due to the inherent molecular defect of containing many unsaturated double bonds, polyisoprene exhibits relatively weak environmental endurance, especially under extreme environmental conditions. To incorporate the excellent features of fluorinated polymer such as tough environmental endurance, a new type of fluorinated polyisoprene is tailored and a facile procedure of introducing fluoroalkyl side chains onto polyisoprene backbone is carried out via epoxidation and thiol–epoxy click chemistry under mild conditions. The results demonstrate that fluorinated alkyl side chains are successfully clicked onto backbone chains of polyisoprene and the corresponding film exhibits a microphase separation structure. As for the fluorinated polyisoprene film after the introduction of fluoroalkyl groups, the water contact angle enhances significantly from 79.4° to 114.8° and the UV reflectivity improves markedly. In addition, the surface chemical constituents confirm that the incorporated fluoroalkyl groups have a tendency to migrate and enrich spontaneously onto the film surface.

Highly sensitive OFET-based gas sensors using fluorinated naphthalenediimide semiconductor films

Naphthalene diimide bearing fluorinated alkyl side chains (FNDI) was synthesized and characterized by NMR spectroscopy. FNDI demonstrated good semiconductor characteristics and was used to fabricate gas sensors based on organic field-effect transistors (OFETs). The designed sensor devices exhibited fast response to low concentrations (1 ppm and less) of ammonia and some aliphatic amines. The revealed high sensitivity of the sensors in combination with the group-selectivity (with respect to amines) and good operational stability makes promising their practical application for food (e.g. fish) quality control or for medical diagnostics.

Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1-n-Fluoro-alkyl-3-methylimidazolium Bis(n-fluoroalkylsulfonyl)amide Ionic Liquids.

The effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis(perfluoroalkylsulfonyl)amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298-343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]), 1-octyl-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8mim][BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8H4F13mim][NTf2]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8H4F13mim][BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids.

Surface modification of seawater desalination reverse osmosis membranes: Characterization studies & performance evaluation

In this work we report surface modification of commercial reverse osmosis membranes by depositing ultrathin copolymer coatings, which could potentially enhance the biofouling resistance of RO membranes. Hydrophilic monomer hydroxyethyl methacrylate (HEMA) and a hydrophobic monomer, perfluorodecyl acrylate (PFDA) were copolymerized directly on the active layer of commercial aromatic polyamide reverse osmosis (RO) membranes using an initiated Chemical Vapor Deposition (iCVD) technique. Attenuated total reflective Fourier transform infrared spectra (ATR-FTIR) verified the successful modification of the membrane surfaces as a new FTIR adsorption band around 1730cm−1 corresponding to carbonyl groups in the copolymer film appeared after the deposition. X-ray Photoelectron spectroscopy (XPS) analysis also confirmed the presence of the copolymer film on the membrane surface by showing strong fluorine peaks emanating from the fluorinated alkyl side chains of the PFA molecules. Contact angle measurements with deionized water showed the modified membrane surfaces to be initially very hydrophobic but quickly assumed a hydrophilic character within few minutes. Atomic Force Microscopy (AFM) revealed that the deposited films were smooth and conformal as the surface topology of the underlying membrane surface remained virtually unchanged after the deposition. FESEM images of the top surface also showed that the typical ridge-and-valley structure associated with polyamide remained intact after the deposition. Short-term permeation tests using DI water and 2000ppm NaCl water showed that the deposited copolymer coatings had negligible effect on permeate water flux and salt rejection.

Comb-Like Fluorinated Polystyrenes Having Different Side Chain Interconnecting Groups

Comb-like fluorinated polystyrenes with different side chain interconnecting groups between backbone and side chain, such as ether (PST−O), thioether (PST−S) and sulfone (PST−SO2), were synthesized in order to examine the effect of the interconnecting groups on the surface order and properties. Near edge X-ray absorption fine structure spectroscopy and grazing incidence wide-angle X-ray diffraction showed that PST−SO2 with very polar sulfone groups exhibited a lower tilt angle of the fluorinated helix to the surface normal as well as higher packing density of fluorinated alkyl side chains than PST−O and PST−S, which have less polar groups. As a result of the ordered structure at the polymer-air interface, PST−SO2 has a smaller surface energy and better stability in water than PST−O and PST−S. These results suggest that the introduction of polar groups to the side chains of comb-like fluorinated polymers can improve the surface properties including the hydrophobicity and stability of fluorinated surfaces.

Water and oil repellency of polysiloxanes with highly fluorinated alkyl side chains

A series of fluorinated polysiloxanes (FLSs) with the 3,3,4,4,5,5,6,6,6-nonafluorohexyl group (C4F9C2H4), 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecyl group (C8F17C3H6), 3-(2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanamido) propyl group [HDFNAG; C8F17(CO)NHC3H6], and 3-(N-methyl-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanamido) propyl group [C8F17(CO)N(CH3)C3H6] were synthesized. Their homopolymers (homo-FLSs) and copolymers with dimethylsiloxane (co-FLSs) were included. The polyester fabrics were treated with these FLSs, and their water and oil repellency was evaluated. These fabrics showed a moderate to good level of water repellency but a poor to zero level of oil repellency, except for those fabrics treated with homo-FLSs with HDFNAG. The characterization of the surface chemical composition by X-ray photoelectron spectroscopy showed that the concentration of fluorine at the surface was not particularly high for poly(ethylene terephthalate) films treated with homo-FLSs with HDFNAG. Differential scanning calorimetry measurements of these FLSs revealed that only homo-FLSs with HDFNAG had a high melting temperature of 75.7°C. These two measurements suggested that the reason the fabrics treated with homo-FLSs with HDFNAG showed good oil repellency was not because the concentration of fluorine at the surface was much higher than for the others but because the reorientation of HDFNAG did not take place for its packing after contact with oil. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1085–1091, 2003

Surface analysis of coating based on novel water‐diluted fluorinated polymer/silica hybrids

AbstractA novel water‐diluted hybrid coating, consisting of fluorinated poly(urethane‐acrylate) (PUA) and colloidal silica, was prepared by introducing a small amount of fluorinated methacrylate units into the PUA chains. The surface composition and surface morphology of the hybrid film were studied extensively. Attenuated total reflectance spectra of infrared analyses showed an enrichment of fluorine‐containing polymer and silica particles on the surface. Using X‐ray photoelectron spectroscopy with Ar+ etching, it was confirmed that a higher concentration than the calculated value of fluorine element was found on the surface of the fluorinated hybrid film, and the amount of silica increased from the very surface to the near surface. The fluorinated alkyl side chains of the fluorinated polymethacrylate were found to orient toward the surface. It is inferred that the silica particles prevent the migration of fluorine‐containing chains for some kind of effect. A comparison of surface topography between the fluorinated PUA film and the fluorinated PUA/SiO2 hybrid film was carried out using atomic force microscopy. Finally, the surface property of the hybrid coating was also determined by contact angle measurement. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 268–274, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10030

Synthesis of fluorosilicone having highly fluorinated alkyl side chains based on the hydrosilylation of fluorinated olefins with polyhydromethylsiloxane

AbstractHydrosilylation of fluorinated olefins with polyhydromethylsiloxane (PHMS) in the presence of a platinum catalyst was investigated to synthesize fluorosilicone having highly fluorinated alkyl side chains (Rf; CnF2n+1). The hydrosilylation of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluoro‐1‐decene (C8F17CHCH2) (1) with poly(dimethylsiloxane‐co‐hydromethylsiloxane) {(CH3)3SiO[(H)CH3SiO]8[(CH3)2 SiO]18Si(CH3)3} (4) converted the hydrogen bonded to silicons into the 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluorodecyl group or fluorine bonded to silicons in the ratio of about 52:48, and the formation of the byproduct C7F15CFCHCH3 (8) was observed. The hydrosilylation of 7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14‐heptadecafluoro‐4‐oxa‐1‐tetradecene (C8F17CH2CH2OCH2CHCH2) (2) with 4 converted the hydrogen bonded to silicons into the 7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14‐heptadecafluoro‐4‐oxa‐tetradocyl group bonded to silicons, but an excess amount of 2 was required to complete the reaction because the isomerization of 2 occurred in part to form C8F17CH2CH2OCHCHCH3 (9). The hydrosilylation of 4,4,5,5,6,6,7,7,8,8,9,9, 10,10,11,11,11‐heptadecafluoro‐1‐undecene (C8F17CH2CHCH2) (3) with 4 converted the hydrogen bonded to silicons into the 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11‐heptadecafluoroundecyl group bonded to silicons. This type of fluorinated olefin was successfully applied to the hydrosilylation with other PHMS's that involved a homopolymer of PHMS and a cyclic PHMS. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3120–3128, 2002

Surface tension of liquid polysiloxanes having fluorinated alkyl side‐chains

AbstractThe surface tension of viscous polymer liquids, viz. polysiloxanes having fluorinated alkyl sidechains, was evaluated based on the pendant‐drop method. The polysiloxane fluids studied are poly‐(3,3,3‐trifluoropropylmethylsiloxane), poly(3,3,4,4,5,5,6,6,6‐nonafluorohexylmethylsiloxane) (PNFHMS), poly(3,3,4,4,5,5,6,6,7,7,8,8‐tridecafluorooctylmethylsiloxane) (PTDFOMS) and poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluorodecylmethylsiloxane) (PHDFDMS). The surface tension of liquid poly(dimethylsiloxane)s was also examined as standard silicone fluids. The surface tensions of liquid PNFHMS, PTDFOMS and PHDFDMS were very low, as low as the value previously reported for poly(oxyhexafluoropropylene) fluids. Low‐ and hightemperature properties of these highly fluorinated polysiloxanes were also evaluated.

Polyimides with Fluorinated Side Chains for Liquid Crystal Alignment

Abstract The surface properties of a series of polyimides with fluorinated alkyl side chains are studied by contact angle and pretilt angle measurements. The contact angles depend on the fluorine content of the polyimides. Higher pretilt angles are obtained for polyimides with longer fluorinated side chains. The pretilt angles, however, not only depend on the side chain length, but also on the main chain structure of the polyimides. Polyimides prepared from benzophenone tetracarboxylic dianhydride are found to show higher pretilt angles than those prepared from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. The anisotropic interaction between polyimide molecules and liquid crystal molecules is discussed.