A comparative structure–property study of methylphenylated and fluoromethylphenylated poly(aryl ethers) and their gas permeabilities and permselectivities

Synthesis of novel poly(arylene ether amide) containing aliphatic ring for optical property

In this work, the monomer N, N′-bis(4-fluorobenzamide)dicyclohexyl methane (BFDCM) was synthesized successfully by 4-fluorobenzoylchloride and 4,4′-diaminodicyclohexylmethane through interfacial reaction, and then the monomer BFDCM and 1,4-benzenediol (HQ) or 4.4′-biphenol (BH) were used to prepare the novel poly(arylene ether amide) (HQ-BFDCM and BH-BFDCM) containing an aliphatic ring in the main chain by nucleophilic substitution in NMP solution. These two polymers exhibited the inherent viscosities ranging from 0.828 to 1.044 dL g−1, high glass-transition temperatures (Tg) of 214.1–235.0 °C, and weight-loss temperature (T5%) of 425.2–441.3 °C. The polymers HQ-BFDCM and BH-BFDCM could completely or partly dissolve in some polar solutions, such as NMP, DMF, and so on, and they showed moderate corrosion resistance. Additionally, the obtained polymers HQ-BFDCM and BH-BFDCM exhibited good optical property, and the optical transmittances of HQ-BFDCM and BH-BFDCM were 74% and 80% at 450 nm, respectively, which showed that they could be applied to the heat-resistant optical films.

Synthesis and gas transport properties of novel poly(ether ether ketone)s containing fluorene group

Two novel gas separation membranes (Phenyl(Ph)-poly(ether ether ketone)s (PEEKs) and PEEKs) based on PEEKs with a high fractional free volume were designed and synthesized. The structure and thermodynamic stability of the membranes were investigated using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The two membranes, which were determined to be high-molecular weight polymers by gel permeation chromatography, showed good solubility in a weakly polar solvent. The gas transport properties of the Ph-PEEK membranes were investigated for different gases (CO2, O2, CH4, and N2) at 25°C and 1 atm. The Ph-PEEK-3 membrane with the largest free volume had the largest gas permeability coefficient and maintained good selectivity. The effect of operating temperature on the gas permeation of the Ph-PEEK-3 membrane was also investigated, and the maximum permeability of the four single gases was reached at 55°C and 1 atm.

Synthesis, properties and gas separation performance of poly(arylene ether sulfone) containing imide pendant groups

Three kinds of pendant imide group were introduced into poly(arylene ether sulfone) via an imidization approach.

Organic–inorganic hybrid proton-conducting electrolyte membranes based on sulfonated poly(arylene ether sulfone) and SiO2–SO3H network for fuel cells

A series of novel organic–inorganic hybrid proton exchange membranes (PEMs) were prepared from the sulfonated poly(arylene ether sulfone) with 4-amino phenyl pendant groups (Am-SPAES), (3-isocyanatopropyl) triethoxysilane (ICPTES), and 3-(trihydroxysilyl) propane-1-sulfonic acid with covalent bonds to form network using a sol-gel method. The obtained cross-linked hybrid membranes (Am-SPAES/I-SiO2-S) displayed excellent solvent resistance and thermal and mechanical stability. The Am-SPAES/I-SiO2-S membranes with cross-linking network exhibited a higher proton conductivity (0.043 S cm−1 at 20°C) than PEMs without covalent bonds (Am-SPAES/SiO2-S) and the swelling ratio maintained below 17.00% even at 100°C. Most importantly, all of the obtained membranes showed considerably lower methanol permeability than that of Nafion 117. In addition, the chemical structures and morphologies of the hybrid membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively.

Asymmetric membranes prepared with trifluoromethylphenylated poly(ether ether ketone) for gas separation

A series of asymmetric membranes based on a trifluoromethylphenylated poly(ether ether ketone) (CF3-PEEK) were prepared using a dry–wet phase inversion method. To obtain the asymmetric membranes with defect-free skin, the type and concentration of internal nonsolvent and the evaporation time were carefully investigated. The cross-section of membranes was characterized by scanning electron microscopy. The gas separation performance of asymmetric membranes was tested in terms of gas permeabilities and selectivities for helium, carbon dioxide (CO2), oxygen (O2), and nitrogen by the constant volume method. It was found that the permeabilities of asymmetric membranes were obviously higher than that of CF3-PEEK dense membrane. The membranes in series 2 showed higher permeability for each gas while the separability for gas pair CO2/O2 increased from 3.78 to about 6 comparing with that of the dense membrane.

Immiscible blends of sulfonated polyetheretherketone and fluorinated polyimide for proton exchange membranes

Both multitrifluoromethylated polyimide (12F-PI) and sulfophenylated polyetheretherketone (Ph-SPEEK) were synthesized in order to build immiscible blends for proton exchange membranes (PEMs). The 12F-PI/Ph-SPEEK blend membranes had improved dimensional stability and oxidation stability in comparison with pure Ph-SPEEK. Despite the introduction of the hydrophobic 12F-PI content, the proton conductivity of blends 1 and 2 showed significantly increased proton conductivity at 80–100°C. The interesting phase-separation morphology, in which the “inorganic-like” particles formed by 12F-PI dispersed in Ph-SPEEK, was observed. This morphology similar to inorganic–organic blends could be highly related to the big differences in the hydrophobicity/hydrophilicity and backbones of two polymers. The obtained results suggest that this series of blend membranes may be potential PEMs for fuel cells.

Structure–property studies on fluorinated polyimide isomers containing biphenyl moieties

Aimed at clarifying the structure–property relationships of fluorinated high-performance polymers, two series of polyimides were synthesized via a two-step thermal imidization derived from isomeric diamine monomers. Furthermore, comparative studies on their properties including solubility, thermal properties, contact angles, refractive indices, dielectric constants and gas permeability were thoroughly performed. Some property differences of the isomers caused by the sequence changes were found.