Fluorocarbon Segments Research Articles

An Ultra-Low-Temperature Elastomer with Excellent Mechanical Performance and Solvent Resistance.

Elastomers presenting good elasticity, ductility, and chemical resistance at low temperatures can serve as superior performers for explorations in extremely cold environments. However, no commercially available elastomer to date can comprehensively fulfill those demands. Here, a perfluoropolyether (PFPE)-based network crosslinked by dynamic urethane chemistry is demonstrated, which may satisfy the demands of application in ultracold environments. As the crucial constitute in such a crosslinked network, PFPE provides the elastomer with excellent elasticity at a temperature down to -110 °Cand outstanding ductility within the cryogenic temperature range. Importantly, the high proportion of fluorocarbon segment also provides wonderful compatibility to most organic solvents, accounting for the low-swelling characteristics of the elastomer in sealing applications. Furthermore, the dynamic crosslinking feature allows the cured elastomer to be reprocessed like thermoplastic polymers, which affords great promise to recycle and reuse the elastomer after its disposal. Inherently, this elastomer would inspire a worldwide interest in the design of elastic devices that are adaptable to extremely low temperature.

Fluorinated α-Helical Polypeptides Synchronize Mucus Permeation and Cell Penetration toward Highly Efficient Pulmonary siRNA Delivery against Acute Lung Injury.

The mucus layer and cell membrane are two major barriers against pulmonary siRNA delivery. Commonly used polycationic gene vectors can hardly penetrate the mucus layer due to the adsorption of mucin glycoproteins that trap and destabilize the polyplexes. Herein, guanidinated and fluorinated bifunctional helical polypeptides were developed to synchronizingly overcome these two barriers. The guanidine domain and α-helix facilitated trans-membrane siRNA delivery into macrophages, whereas fluorination of the polypeptides dramatically enhanced the mucus permeation capability by ∼240 folds, because incorporated fluorocarbon segments prevented adsorption of mucin glycoproteins onto polyplexes surfaces. Thus, when delivering TNF-α siRNA intratracheally, the top-performing polypeptide P7F7 provoked highly efficient gene knockdown by ∼96% at 200 μg/kg siRNA and exerted pronounced anti-inflammatory effect against acute lung injury. This study thus provides an effective strategy for transmucosal gene delivery, and it also renders promising utilities for the noninvasive, localized treatment of inflammatory pulmonary diseases.

Time-of-Sight Liquid Flow Measurements in the Low Nanoliters per Minute Scale.

We describe an affordable and robust measurement technique applicable to nanoscale liquid flow. The approach can provide good precision (<1% RSD) in the 1.5-15 nL/min flow range. The motion of a conductive/nonconductive immiscible segmental interface in a capillary is followed by an admittance detector. The conductive marker segment, e.g., a salt solution, is protected on both sides from the principal flow stream by immiscible guard segments, typically a fluorocarbon (FC) liquid, of significantly greater impedance. Fluorosilylation of the capillary ensures no other liquid film between the FC segments and the wall (perfect piston). A given interface/marker can typically be used only once in interface/front tracking systems. We overcome this by putting the sensor capillary in a valved configuration where the flow direction in the sensor is reversed before the guard/marker segments escape. Several strategies are possible to interpret flow rate from the sensor output, including the rate of the interface movement. During the measurement process, a change in this rate of movement can be detected in <1 s. Small temperature variations in the 25-35 °C range did not affect sensor behavior.

Growth of a Surface-Tethered, All-Carbon Backboned Fluoropolymer by Photoactivated Molecular Layer Deposition.

The synthesis of an all-carbon backboned fluoropolymer using photoactivated molecular layer deposition (pMLD) is developed. pMLD is a vapor-phase, layer-by-layer, organic thin film synthesis method utilizing UV light, allowing for the creation of materials previously unavailable via thermal MLD. The carbon backbone is achieved by reacting an iodine-containing fluorocarbon monomer (1,4-diiodooctafluorobutane) and a diene monomer (1,5-hexadiene) under UV irradiation in a step-growth polymerization sequence. The polymerization occurs with a growth rate of 1.3 Å/cycle, forming a copolymer containing hydrocarbon and fluorocarbon segments. X-ray photoelectron spectroscopy (XPS) was used to confirm the formation of new carbon-carbon bonds and quantify the final film composition. In situ XPS thermal annealing experiments confirm the film stability up to 400 °C. The ability to pattern the fluoropolymer on a surface is demonstrated using a photomask, suggesting that these films could be incorporated into photolithographic processes. Together, these results demonstrate that pMLD can be used to synthesize carbon backboned films with photopatterning ability, expanding the available chemistries and potential applications of MLD polymers.

Unsymmetrical Spiroalkanedithiols Having Mixed Fluorinated and Alkyl Tailgroups of Varying Length: Film Structure and Interfacial Properties.

A custom-designed series of unsymmetrical spiroalkanedithiols having tailgroups comprised of a terminally fluorinated chain and a hydrocarbon chain of varying lengths were synthesized and used to prepare self-assembled monolayers (SAMs) on gold substrates. The specific structure of the adsorbates was of the form [CH3(CH2)n][CF3(CF2)7(CH2)8]C[CH2SH]2, where n = 7, 9, and 15 (designated as F8H10-C10, F8H10-C12, and F8H10-C18, respectively). The influence of the length of the hydrocarbon chain in the bidentate dithiol on the structure and interfacial properties of the monolayer was explored. A structurally analogous partially fluorinated monodentate alkanethiol and the corresponding normal alkanethiols were used to generate appropriate SAMs as reference systems. Measurements of ellipsometric thickness showed an unexpectedly low film thickness for the SAMs derived from the bidentate adsorbates, possibly due to disruptions in interchain packing caused by the fluorocarbon chains (i.e., phase-incompatible fluorocarbon-hydrocarbon interactions), ultimately giving rise to loosely packed and disordered films. Analysis by X-ray photoelectron spectroscopy (XPS) were also consistent with a model in which the films were loosely packed; additionally, the XPS spectra confirmed the attachment of the sulfur headgroups of the bidentate adsorbates onto the gold substrates. Studies of the SAMs by polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) suggested that as the length of the hydrocarbon chain in the adsorbates was extended, a more ordered surface was achieved by reducing the tilt of the fluorocarbon segment. The wettability data indicated that the adsorbates with longer alkyl chains were less wettable than those with shorter alkyl chains, likely due to an increase in interchain van der Waals forces in the former.

Synthesis, self-assembly and pH sensitivity of a novel fluorinated triphilic block copolymer

A novel fluorinated triblock copolymer incorporating 2-ethylhexyl methacrylate (EHMA), tert-butyl methacrylate (tBMA) and 1H,1H,2H,2H-perfluorodecyl acrylate (FA) (PEHMA-b-PtBMA-b-PFA) was first synthesized using three successive reversible addition fragmentation chain transfer (RAFT) polymerization and the subsequent hydrolyzing at acidic condition. The as-fabricated triblock copolymer exhibited an interesting morphology evolution from the multi-compartment rod-like structure to spherical structure along with the addition of a selective solution. At the same time, a visible phase separation domain could be seen in the core area due to the existence of fluorocarbon segments. Furthermore, the self-assembly behavior of the triphilic copolymer at different pH was also verified by transmission electron microscopy, as well as the dynamic light scattering. These stimuli-responsive multi-compartment nanostructures may have potential applications in drug delivery.

Lateral Diffusion and Molecular Interaction in a Bilayer Membrane Consisting of Partially Fluorinated Phospholipids.

Fluorinated lipids and surfactants are attractive biomimetic materials for the extraction and reorganization of membrane proteins because of the biological inertness of fluorocarbons. We investigated the fundamental physical properties of a partially fluorinated phospholipid (F4-DMPC), such as phase transition, area thermal expansion, and lateral lipid diffusion, to evaluate the intermolecular interaction of F4-DMPC in the hydrophobic region quantitatively on the basis of free-volume theory. Fluorescence microscope observation of the supported lipid bilayer (SLB) of F4-DMPC showed that the phase transition between the liquid crystalline and gel phases occurred at 5 °C and that the area thermal expansion coefficient was independent of the temperature near the phase transition temperature. We performed a single particle tracking of the F4-DMPC-SLB on a SiO2/Si substrate, to measure the diffusion coefficient and its temperature dependence. The apparent activation energy (E'a) of lateral lipid diffusion, which is an indicator of intermolecular interaction, was 39.1 kJ/mol for F4-DMPC, and 48.2 kJ/mol for a nonfluorinated 1,2-dioleoyl-sn-glycero-3-phosphocholine as a control. The difference of 9 kJ/mol in E'a was significant compared with the difference due to the acyl chain species among nonfluorinated phosphatidylcholine and also that caused by the addition of cholesterol and alcohol in the bilayer membranes. We quantitatively evaluated the attenuation of intermolecular interaction, which results from the competition between the dipole-induced packing effect and steric effect at the fluorocarbon segment in F4-DMPC.

Balancing Surface Hydrophobicity and Polarizability of Fluorinated Dielectrics for Organic Field‐Effect Transistors with Excellent Gate‐Bias Stability and Mobility

It is demonstrated that treating dielectrics with fluorinated polymers, which have excellent hydrophobicity, chemical inertness, and the lowest polarizability, yields a semiconductor‐compatible surface energy and excellent charge detrapping characteristics. Fluorocopolymers, polystyrene‐random‐poly(2,3,4,5,6‐pentafluorostyrene) (PS‐r‐PPFS) copolymers with different 2,3,4,5,6‐pentafluorostyrene (PFS) loadings, are synthesized to modify a SiO2 gate dielectric using radical polymerization. Surface energy (γ) of the copolymer‐treated SiO2 dielectrics decreases from 40.7 to 24.0 mJ m−2 with increasing PFS mol% in the copolymer. Pentacene organic field‐effect transistors (OFETs) show field‐effect mobility (μFET) values ranging from 0.82 (for 0 mol% PFS) to 0.25 cm2 V−1 s−1 (for 100 mol% PFS). Enhancing the bias stress stability without affecting the μFET value is achieved via the introduction of a small mol% fluorocarbon segments onto the PS‐r‐PPFS backbone. 15 mol% PFS‐loaded fluorocopolymer‐coated SiO2 substrate yields a γ value of 35 mJ m−2, close to that (38 mJ m−2) of the lowest‐γ crystal surface of pentacene, and the corresponding OFETs have μFET values up to 0.81 cm2 V−1 s−1 and excellent gate‐bias stress stability in comparison to the rich fluorinated dielectric systems, which has degraded μFET values ranging from 0.2 to 0.4 cm2 V−1 s−1.

Self-Assembled Monolayers Generated from Unsymmetrical Partially Fluorinated Spiroalkanedithiols.

Self-assembled monolayers (SAMs) were prepared on gold substrates from an unsymmetrical partially fluorinated spiroalkanedithiol adsorbate with the specific structure of [CH3(CH2)7][CF3(CF2)7(CH2)8]C[CH2SH]2 (SADT) and compared to SAMs formed from the semifluorinated monothiol F8H10SH [CF3(CF2)7(CH2)10SH] of analogous chain length and n-octadecanethiol. The adsorbate with two alkyl chains, one terminally fluorinated and the other nonfluorinated, was designed to form monolayers in which the bulky helical fluorocarbon segments assemble on top of an underlying layer of well-packed trans-extended alkyl chains. Different combinations of deposition solvents and temperatures were used to produce the bidentate SAMs. Characterization of the resulting monolayers revealed that SAMs formed in DMF at room temperature allow complete binding of the sulfur headgroups to the surface and exhibit higher conformational order than those produced using alternative solvent/temperature combinations. The reduced film thicknesses and enhanced wettability of the SADT SAMs, as compared to the SAMs generated from F8H10SH, suggest loose packing and an increase in the tilt of the terminal fluorocarbon chain segments. Nevertheless, the density of the underlying hydrocarbon chains of the SADT SAMs was higher than that of the F8H10SH SAMs, owing to the double-chained structure of the new adsorbate. The conformational orders of the SAM systems were observed to decrease as follows: C18SH > F8H10SH > SADT. However, the SAMs formed from this new double-chained bidentate adsorbate in DMF expose a fluorinated interface with a relatively low surface roughness, as determined by contact-angle hysteresis.

Synthesis, physicochemical characterization, and self-assembly of linear, dibranched, and miktoarm semifluorinated triphilic polymers.

Linear, dibranched and miktoarm amphiphiles containing both hydrophobic and fluorophilic moieties were synthesized and characterized in an attempt to elucidate the relationship between semi-fluorinated amphiphile structure and aggregate behaviour in aqueous solution. For the linear and dibranched amphiphiles, there was an exponential decrease in critical aggregation concentration (CMC) and a logarithmic increase in core microviscosity with increasing length of the fluorocarbon segments; while the miktoarm architecture produced no notable trend in microviscosity or CMC. Furthermore, the linear and dibranched surfactants showed enhanced kinetic stability, dissociating more slowly in the presence of human serum than did either the dibranched or miktoarm amphiphiles. Finally, encapsulation studies with the hydrophobic drug paclitaxel (PTX) showed that the ability to solubilize and retain PTX increased with the presence and with the increasing size of the fluorocarbon moiety for both the linear and dibranched amphiphiles, while no such trend was observed for the miktoarm amphiphiles.

Facile access to cytocompatible multicompartment micelles with adjustable Janus-cores from A-block-B-graft-C terpolymers prepared by combination of ROP and ATRP

The architecture of hydrophobic segments can determine the specific morphology of multicompartment micelles (MCMs) that are generated from aqueous assembly of amphiphilic terpolymers. In this study, we aimed to design and generate poly(ɛ-caprolactone)-based multicompartment micelles with adjustable Janus-cores. Well-defined terpolymers with a novel A-block-B-graft-C architecture composed of biologically compatible polymers, methoxy poly(ethylene glycol) (PEG), poly(ɛ-caprolactone) (PCL) and poly(2-(perfluorobutyl)ethyl methacrylate) (PPFEMA), were prepared by the stepwise use of ring-opening polymerization and atom transfer radical polymerization. Characterization of the obtained terpolymers was carried out by 1H NMR and gel permeation chromatography. Results from differential scanning calorimetry and X-ray diffraction studies indicated that within the terpolymer structure, the PCL segments are in the crystalline state, while fluorocarbon segments belong to the amorphous domains. Due to the thermodynamic incompatibility of PCL and PPFEMA, MCMs could be obtained upon aqueous self-assembly of the terpolymer. The well-segregated Janus-cores with adjustable compartment balance were revealed by transmission electron microscopy. In vitro cell viability assays further demonstrated an excellent cytocompatibility of the MCMs both in mouse embryonic fibroblasts (3T3) and human acute monocytic leukemia (THP-1) cells.

Structure of Self-Assembled Monolayers of Partially Fluorinated Alkanethiols on GaAs(001) Substrates

A series of self-assembled monolayers (SAMs) of partially fluorinated alkanethiols (PFAT) with variable length of the fluorocarbon segment, viz. F(CF2)n(CH2)11SH (FnH11SH, n = 6, 8, and 10) were prepared on GaAs(001) and characterized by several complementary spectroscopic techniques. The SAMs were found to be well ordered and densely packed, and thus able to protect the substrate from oxidation, with the highest quality F10H11SH monolayer being most effective in this regard. The packing density of the SAMs was governed by the bulky fluorocarbon segments having a helical conformation. With decreasing length of these segments, a slight decrease in the packing density accompanied by progressive deterioration of the orientational order and a slight disturbance of the conformational order in the fluorocarbon part of the films occurred. In contrast, the hydrocarbon segments of the FnH11SH SAMs exhibited similar average orientation in all studied monolayers, accompanied by a partial conformational disorder. This was explained by the effect of a strong bending potential favoring a substrate–S–C angle of ∼104° and predefining, thus, the orientation of the hydrocarbon segments.

Structure of Self-Assembled Monolayers of Partially Fluorinated Alkanethiols with a Fluorocarbon Part of Variable Length on Gold Substrate

A series of self-assembled monolayers (SAMs) formed on Au(111) from partially fluorinated alkanethiols (PFAT) with variable length of the fluorocarbon chain, viz. F(CF2)n(CH2)11SH (FnH11SH, n = 6, 8, and 10), was studied by high resolution X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and near edge X-ray absorption fine structure spectroscopy. The SAMs were found to be highly ordered and densely packed. The packing density was governed by the bulky fluorocarbon segments which adopted a helical conformation typical of this entity. With decreasing length of the fluorocarbon segment, progressive deterioration of the orientational order accompanied by a slight decrease in the packing density was observed in the fluorocarbon part of the FnH11SH SAMs. The conformation of the fluorocarbon segment was persistent through the series, with probably only a minor deterioration for n = 8 and 6. The hydrocarbon segments of the monolayers were, however, unaffected by the deterioration of the orientational order in the fluorocarbon part. They persistently exhibited all trans planar conformation, typical of densely packed assemblies of these moieties, while their orientation, given by the characteristic tilt and twist angles, mimicked that of the nonsubstituted alkanethiolate SAMs on Au(111). This behavior is explained by the effect of the bending potential which predefines the orientation of the hydrocarbon segments even if they are separated beyond the equilibrium spacing by the bulky fluorocarbon moieties.

The surface chemical composition and structure of a fluorocarbon–hydrocarbon block copolymer

The thermal properties of the fluorocarbon–hydrocarbon copolymer [‐(CF2)8‐(CH2)10‐]N were characterized using polarized optical microscopy, differential scanning calorimetry and X‐ray diffraction. The results revealed the presence of a crystalline phase and a threaded nematic liquid crystal phase. The changes in the surface composition during annealing were studied in situ using time‐of‐flight secondary ion mass spectrometry. The spectra were interpreted using principal component analysis (PCA). The surface compositions at different thermal states can be distinguished by PCA. Moreover, a PCA loadings analysis revealed a continuous increase in the concentration of the hydrocarbon segments on the surface as the polymer gradually changed from the amorphous state to the liquid crystal state and finally the crystalline state. This suggests that the chemical composition of the surface in the amorphous state is controlled by the surface energy difference between the fluorocarbon and hydrocarbon segments, while the surface composition in the crystalline state is controlled by the structural ordering of the fluorocarbon segments. The results also showed that the surface re‐construction of this polymer was highly reversible. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Supercritical carbon dioxide swelling of fluorinated and hydrocarbon surfactant templates in mesoporous silica thin films

The penetration of compressed CO2 in hydrocarbon and fluorocarbon regions of concentrated surfactant mesophases are interpreted from differences in the CO2-processed pore expansion of mesoporous silica thin films templated by three surfactants containing varying degrees of hydrocarbon and fluorocarbon functionality. Ordered silica thin films are synthesized for the first time using the 16-carbon (C16) partly fluorinated surfactant, 11,11,12,12,13,13,14,14,15,15,16,16,16-tridecafluorocetyl pyridinium bromide (HFCPB), as a templating agent. Silica films templated with surfactants containing a 8-carbon (C8) fluorocarbon tail (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl pyridinium chloride (HFOPC)) and a 16-carbon (C16) hydrocarbon tail (cetyl pyridinium bromide (CPB)) and HFCPB (C16) are processed in compressed CO2 (69–172bar, 25°C and 45°C) during synthesis. CO2 processing results in significant pore expansion for films templated with both fluorinated surfactants, while pore expansion is negligible for the hydrocarbon templated material suggesting that preferential CO2 penetration occurs in the ‘CO2-philic’ fluorocarbon segments of the surfactant template. The effect of substrate surface energy on the final uniformity of the dip-coated films is studied by varying the substrate from unmodified glass to a fluorocarbon-capped substrate. The ability to create dip-coated thin films on low surface energy substrates through favorable interaction of surfactant template tail with the substrate surface functional groups is demonstrated.

Solution-Phase Desorption of Self-Assembled Monolayers on Gold Derived From Terminally Perfluorinated Alkanethiols

The solution-phase thermal desorption of three series of self-assembled monolayers (SAMs) on gold generated from terminally perfluorinated alkanethiols was examined. Series 1 SAMs, F(CF2)x(CH2)11SH, where x = 1–10, consisted of a constant hydrocarbon segment length with an increasing fluorocarbon segment length. Series 2 SAMs, F(CF2)10(CH2)ySH, where y = 2–6, 11, consisted of a constant fluorocarbon segment length with an increasing hydrocarbon segment length. Series 3 SAMs, F(CF2)x(CH2)ySH, where x = 1–10 and y = 16 – x, consisted of both hydrocarbon and fluorocarbon segments in which the segment lengths were varied while holding the total chain length constant at 16 carbon atoms. SAMs from these three series were prepared and characterized using both ellipsometry and contact-angle measurements. The resultant SAMs were shown to be highly hydrophobic and oleophobic. The SAMs were heated in decalin (DC) and perfluorodecalin (PFD) at 80 °C for various periods of time to monitor their thermal stability when exposed to hydrocarbon versus fluorocarbon solvents. In general, SAMs derived from n-alkanethiols and terminally perfluorinated alkanethiols exhibited diminished thermal stabilities upon heating in a hydrocarbon solvent (DC) versus heating in a perfluorocarbon solvent (PFD). The thermal stability of the SAMs increased with increasing lengths of the CF2 or CH2 segments. We also examined the kinetics of thermal desorption of these SAMs. From these studies, SAMs composed of higher degrees of terminal perfluorination exhibited smaller rate constants for the initial stage (fast regime) of desorption. When compared with analogous alkanethiol SAMs, the terminally perfluorinated SAMs exhibited greater thermal stabilities in both DC and PFD. In addition, values of the rate constants for desorption of the alkanethiol SAMs were approximately double those of the terminally perfluorinated SAMs having similar chain lengths.

Influence of fluorinated segments of variable length on the thickening properties of a model HASE skeleton

AbstractIntroduction of fluorocarbon segments in an associative thickener copolymer (ethyl acrylate (EA)/methacrylic acid/macromonomer) was achieved by the substitution of EA with either trifluoroethyl acrylate, 2‐perfluorobutylethyl acrylate, or 2‐perfluorooctylethyl acrylate. The thickening properties were evaluated by rheological flow experiments in aqueous medium as well as in 10 wt % of sodium dodecyl sulfate (SDS) aqueous solution. Whereas in the literature no particular attention is devoted to the impact of the ethylene moieties in hydrophobically modified alkali‐soluble emulsion (HASE) skeleton, our study reveals they contribute significantly to the performances when modified by an incompatible fluorocarbon segment. Moreover, the synthesis process has a huge influence by inducing a specific distribution of the fluorinated acrylates in the macromolecule. The amount of substitution is also important and even 20 mol % of EA substituted reveals a great impact on the rheological properties of the copolymer solutions. Whereas an SDS aqueous medium generally destroys almost all the hydrocarbon interactions from the macromonomer, the total replacement of ethyl groups by trifluoroethyl groups with a cosolvent process, leads to emulsions with an equivalent thickening effect than the reference hydrocarbon HASE used. This result is quite encouraging for research work on the synthesis of HASE with increased biocompatibility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A unified morphological description of Nafion membranes from SAXS and mesoscale simulations

Although many different structural models have been proposed for perfluorosulfonic acid (PFSA) ionomers such as Nafion, the very high degree of disorder in these materials makes it difficult, if not impossible, to deduce their morphology unambiguously from small angle X-ray and neutron scattering (SAXS/SANS) experiments alone. We present a combination of a model-independent procedure for obtaining structural information from SAXS patterns based on a Maximum Entropy (MaxEnt) approach coupled with mesoscale simulations of the morphology of Nafion using Dissipative Particle Dynamics (DPD) parameterized with atomistic calculations and density functional theory. These two methods show that the nanoscale ionic clustering in PFSAs is intimately linked to, but spatially separate from, the larger scale organization of the fluorocarbon backbone. Although we are unable to directly observe crystallization of the backbone in the DPD simulations, the high density regions of fluorocarbon segments correspond exactly to those regions where the density of ionic clusters is lowest, each forming an independent bicontinuous domain. We are thus able to demonstrate a unified morphological description of PFSAs based on both statistical (MaxEnt) and thermodynamic (DPD) descriptions, which broadly favours a bicontinuous network of ionic clusters embedded in a matrix of fluorocarbon chains.

ChemInform Abstract: Perfluorocyclobutane (PFCB) Polyaryl Ethers: Versatile Coatings Materials.

Abstract The cyclopolymerization of aromatic trifluorovinyl ether (TFVE) monomers offers a versatile route to a unique class of linear and network fluoropolymers containing the perfluorocyclobutyl (PFCB) linkage. Polymerization proceeds by a thermal — radical mediated — step-growth mechanism and provides well-defined polymers containing known fluoroolefin end groups. PFCB polymers combine the engineering thermoplastic nature of polyaryl ethers with fluorocarbon segments and exhibit excellent processability, optical transparency, high temperature performance, and low dielectric constants. An intermediate strategy utilizing Grignard and aryllithium reagents has been developed which offers access to a wide variety of hybrid materials amenable to coatings applications. Liquid crystalline examples have recently been achieved in addition to tailoring optical properties by co-polymerization.

Synthesis and surface activities of organic solvent-soluble fluorinated surfactants

A variety of fluorinated surfactants soluble in organic solvent were prepared, including C 8F 17SO 2NHC n H 2 n+1 ( n = 2, 4, 6, 8, 10), C 8F 17SO 2NHR (R = C 6H 11, C 6H 5), C 8F 17SO 2N(C n H 2 n+1 ) 2 ( n = 1, 2, 3, 4) and C 8F 17SO 2NH(CH 2) n NHO 2SC 8F 17 ( n = 6, 10). Their surface activities in various organic solvents were determined by surface tension measurement. The results showed that these fluorinated surfactants can reduce the surface tension of both polar and non-polar organic solvents. In general, organic solvents with strong polarity or long alkyl chain are beneficial to increase the surface activity of these polar fluorinated surfactants. By comparing fluorinated surfactants with the same fluorocarbon segment and connecting group, C 8F 17SO 2N(C n H 2 n+1 ) 2 ( n = 1, 2, 3, 4) showed lower surface activity in organic solvents than C 8F 17SO 2NHC n H 2 n+1 ( n = 2, 4, 6, 8) with an equal carbon number of the solvophilic group. Through surface tension vs. concentration curves given for N-octyl perfluorooctanesulfonamide in various organic solvents, a break point like the critical micelle concentration of ordinary surfactants in aqueous solutions was observed, and the effect of the different types of organic solvents on adsorption and aggregation behavior was also studied.