Fluorinated high-performance polymers: Poly(arylene ether)s and aromatic polyimides containing trifluoromethyl groups

Synthesis and gas transport properties of novel functional polyimide/ZnO nanocomposite thin film membranes

In this study, the synthesis, morphology, thermal properties and gas transport of new polyimide/ZnO nanohybrid films were investigated.

Synthesis of Highly Sulfonated Poly(arylene ether) Containing Multiphenyl for Proton Exchange Membrane Materials

A series of sterically hindered, sulfonated, poly(arylene ether) polymers were synthesized by nucleophilic polycondensation reaction using 4,4′′′′-difluoro-3,3′′′′-bistrifluoromethyl-2′′,3′′,5′′,6′′-tetraphenyl-[1,1′;4′,1′′;4′′,1′′′;4′′′,1′′′′]-pentaphenyl and 4,4′-biphenol and were prepared through postpolymerization sulfonation. The chemical structures were confirmed by1H NMR. Subsequent to sulfonation, solvent-casting membranes were provided ion exchange capacity (IEC) values ranging from 0.39 to 2.90 mmol/g. Proton conductivities of membranes ranged from 143 to 228 mS/cm at 80°C under fully humidified conditions which were higher than that of Nafion 117. The membrane also exhibited considerably dimension stability, oxidative stability, and hydrolytic stability. The microphase structure was investigated by transmission electron microscopy (TEM) and the ionic aggregation of sulfonic acid groups exhibited spherical ionic clusters with well-developed phase separated morphology. The results indicated that the membranes are promising candidates for application as proton exchange membranes. This investigation demonstrates introducing multiphenylated moieties to create a high free volume polymer that provides dimensionally stable and high proton conductivity membranes.

Synthesis of quaternary α-perfluoroalkyl lactams via electrophilic perfluoroalkylation

The efficient one-pot perfluoroalkylation of lactams by hypervalent iodine reagents is catalysed by trimethylsilyl triflimide.

Optical Properties of Some Fluorinated Poly(1,3,4-Oxadiazole-Ether)s in Homogeneous and Heterogeneous Media. Changes Induced by SnO2, NiO and SnO2/NiO Mixed-Oxide Nanoparticles

Optical characteristics of some fluorinated poly(1,3,4-oxadiazole-ether)s in presence of SnO2, NiO and SnO2/NiO mixed-oxide nanoparticles (NPs) was investigated. The interactions between polymers and metal oxide NPs were studied by steady-state UV-Vis absorption and fluorescence spectroscopy techniques. The absorption and fluorescence signals of all investigated polymers was modified by presence of both pure and mixed-oxide nanoparticles. The moderate values of Stern-Volmer quenching constant and non-linear trend of Scott plot indicate the less affinity between metal oxide NPs and polymers. The solvation behavior of some fluorinated poly(1,3,4-oxadiazole-ether)s in chloroform-N,N-dimethylformamide and N,N-dimethylformamide-dimethylsulfoxide mixtures was discussed.

Efficient Palladium-Catalyzed C-H Fluorination of C(sp3)-H Bonds: Synthesis of β-Fluorinated Carboxylic Acids

A novel and facile process for direct fluorination of unactivated C(sp3)-H bonds at the β position of carboxylic acids was accomplished by a palladium(II)-catalyzed C-H activation. The addition of Ag2O and pivalic acid was found to be crucial for the success of this transformation. This reaction provides a versatile strategy for the synthesis of β-fluorinated carboxylic acids.

The influence of conformational parameters on some physical properties of polyimides containing naphthalene units

Conformational parameters of some aromatic polyimides–containing naphthalene units have been calculated by Monte Carlo method taking into consideration the hindered rotation produced by voluminous naphthalene units. Several physical properties such as solubility, glass transition temperature ( Tg), and initial decomposition temperature ( Td) have been studied with regard to the rigidity of the chain of these polyimides. It has been shown that Tg is well correlated with chain rigidity and with free volume ( Vfr) of the polymers, while the Td is not influenced by conformational parameters.

Dielectric and gas transport properties of highly fluorinated polyimides blends

The physicochemical properties of highly fluorinated polyimide blends were studied in order to highlight the advantages of employing a high content of fluorine atoms to tailor the properties of polyimide materials. Thus, dynamo-mechanical analysis was used to evidence the physical phenomena taking place during heating. The trend of storage modulus, loss modulus and loss factor tangent with temperature during and after the α relaxation was explored. The dielectric spectroscopy was carried out to investigate the dielectric behaviour at different temperatures and frequencies and to evaluate the values of dielectric constant, dielectric loss and electrical resistance. The dielectric spectroscopy data were corroborated with the dynamo-mechanical analysis to highlight the sub-glass transitions encountered in these blend films. Dielectric loss diagrams showed sub-glass transitions in the form of γ and β relaxations mainly due to the segmental mobility of the polymer chain components. The gas separation performance of some of the investigated blends was assesed, and their ability to achieve simultaneously higher gas permeability and higher selectivity was demonstrated.

Direct fluorination of styrenes

We have developed a practical method to synthesize fluorostyrene compounds. A mild and regioselective mono-fluorination reaction occurred smoothly for various di- and trisubstituted styrenes in the presence of RuCl3 and N-fluorobenzenesulfonimide (NFSI). A tandem alkyne hydroarylation-olefin fluorination reaction was also developed using an Au catalyst.

Synthesis and characterization of new soluble polyimides based on pyridine unit with flexible linkages

A series of new polyimides were synthesized by condensation of pyridine-bridged novel diamine monomers, bis(4-aminobenzoyloxy-3,5-dimethyl phenyl)-3′-pyridyl methane and 2,6-bis(2-amino-3-pyridyloxy)pyridine, with various aromatic anhydrides. The monomers and precursors were characterized by elemental analysis, Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and carbon-13 nuclear magnetic resonance (13C NMR) spectroscopic techniques. The structure of the polymers were characterized by FTIR and 1H-NMR spectroscopy, and the physical properties of the polymers, including the glass transition temperature (in the range of 199–319°C), thermal and thermo-oxidative stability (10% weight loss temperature is in the range of 375–539°C in air and 403–542°C in nitrogen atmospheres), the char yield in the range of 37.91–56.65% at 800°C, solubility, solution viscosity (0.81–1.81), molecular weight data, optical properties, crystallinity, mechanical properties like tensile strength (86–102 MPa), elongation at break (12.5–16.5%), tensile modulus (1.2–1.8 GPa), and moisture absorption were also studied.

Poly(arylene ether ketone)s with pendant porphyrins: synthesis and investigation on optical limiting properties

A series of poly(arylene ether ketone)s with porphyrin pendants were synthesized, which exhibited superior NLO, optical limiting and good thermal properties as novel polymer NLO materials.

High refractive index and low-birefringence polyamides containing thiazole and naphthalene units

Highly refractive and solution processable polyamides (PAs) were synthesized by the introduction of thiazole rings, naphthalene groups, and thioether linkages.

Structure–property relationship of polyetherimide based on aromatic dianhydride and long alkyl chain containing aromatic diamines

A series of new poly(ether imide)s (PEIs) were synthesized from different commercially available dianhydrides like 3,3′,4,4′-benzophenonetetracarboxylic dianyhride (BTDA) and pyromellitic dianhydride (PMDA) and diamines like 1,4-bis(4-aminophenoxy)propane, 1,4-bis(4-aminophenoxy)butane, 1,4-bis(4-aminophenoxy)pentane, and 1,4-bis(4-aminophenoxy)hexane by a typical two-step polymerization method. The structure of the monomers and PEIs prepared were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectral analysis. Solubility of the PEIs was tested in various organic solvents. Thermal properties of the PEIs were investigated by thermogravimetric analysis and differential scanning calorimetry. The temperature corresponding to 5% ( T5%) and 10% ( T10%) weight loss are from 318°C to 418°C and from 380°C to 480°C, respectively. These PEIs exhibit glass transition temperature in the range of 195–245°C, very low water absorption (0.37–0.62%), and low dielectric constant (2.68–3.17) at 1 MHz. The PEIs film possessed good mechanical properties with tensile strength of 77–98 MPa, elongation at break of 8–13%, and tensile modulus of 1.5–2.2 GPa. These results imply that the synthesized PEIs are well suited to be used as dielectric materials. Based on these studies the structure–property relationships were established.

Postpolymerization of a fluorinated and reactive poly(aryl ether): an efficient way to balance the solubility and solvent resistance of the polymer

A new fluorinated poly(aryl ether) with reactive benzocyclobutene groups as the side chain was successfully synthesized. This polymer showed a number-average molecular weight (Mn) of 200,000 and had good solubility and film-forming ability. After being postpolymerized at high temperature (>200 °C), the polymer film converted to a cross-linked network structure, which was insoluble in the common organic solvents. Such results suggest that the postpolymerization is an efficient way to achive the balance between the solubility and the solvent resistance of the polymer. TGA data showed that the postpolymerized polymer had a 5 wt % loss temperature at 495 °C and a residual of 61% at 1000 °C under N2. The cross-linked film also exhibited good dielectric properties with an average dielectric constant of about 2.62 in a range of frequencies from 1 to 30 MHz. With regard to the mechanical properties, the cross-linked film had hardness, Young's modulus, and bonding strength to a silicon wafer of 1.22, 8.8, and 0.89 GPa, respectively. These data imply that this new polymer may have potential applications in the electrical and microelectronics industry.

Double-layer ionomer membrane for improving fuel cell performance

A double-layer ionomer membrane, thin-layer Nafion (perfluorinated sulfonic acid polymer) on a sulfonated aromatic block copolymer (SPK-bl-1), was prepared for improving fuel cell performance. Each component of the double-layer membrane showed similar phase-separated morphologies to those of the original membranes. A fuel cell with the double-layer membrane exhibited lower ohmic resistance and higher cathode performance than those with the original SPK-bl-1 membrane despite their comparable water uptake and proton conductivity. Detailed electrochemical analyses of fuel cell data suggested that the thin Nafion interlayer contributed to improving the interfacial contact between the SPK-bl-1 membrane and the cathode catalyst layer and to mitigating excessive drying of the membrane. The results provide new insight on designing high-performance fuel cells with nonfluorinated ionomer membranes such as sulfonated aromatic polymers.