[en] A series of reinforced composite membranes were prepared from Nafion 212 and crosslinkable fluorine-containing polyimide (FPI) with various crosslinkers. The crosslinkable FPI reacts with the crosslinkers and forms semi-interpenetrating polymer networks (semi-IPN) structure with Nafion 212. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and chemical oxidation stability of the composite membranes are studied. The degree of crosslinking is characterized by gel fraction of the composite membranes. Compared to pure Nafion 212, the composite membranes exhibit excellent thermal stability, improved mechanical properties and dimensional stability. The tensile strength of the composite membranes is in the range of 37.3-51.2 MPa. All the composite membranes exhibit high proton conductivity which ranges from 1.9 x 10^-2 to 9.9 x 10^-2 S cm^-1. The proton conductivity of the composite membrane with 2-propene-1-sulfonic acid sodium salt (SAS) as the crosslinker is 9.9 x 10^-2 S cm^-1 at 100 ^oC which is similar to that of Nafion 212 under the same condition.

[en] A new series of six-member sulfonated copolyimides (SPIs) were prepared by one-step solution copolycondensation from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 1,2-dihydro-2-(4-amino-2-sulfophenyl)-4- [4-(4-amino-2-sulfonphenoxy)-phenyl] (2H)phthalazin-1-one (S-DHPZDA), 4,4'-bis(4-aminophenoxy) biphenyl (BAPB) and 1,2-dihydro-2-(4-aminophenyl)-4-[4-(4-(aminophenoxyl)phenyl)] (2H)phthalazin-1-one (DHPZDA). The sulfonation degree (DS) of the SPIs was controlled by the mol ratio of the sulfonated diamine and non-sulfonated diamine. The obtained SPI membranes had excellent thermal stability, high mechanical property and proton conductivity as well as low methanol permeability. The tensile strength of the SPI membranes was ranging from 54.7 to 98.1 MPa, which was much higher than that of Nafion. The SPI membranes exhibited high proton conductivity (σ) and low methanol permeability ranged from 10^-3 to 10^-2 S/cm and 10^-8 to 10^-7 cm²/s depending on the DS of the polymers, respectively.

[en] The reinforced composite membranes based on Nafion^® membranes attract a lot of attention as proton exchange membrane (PEM) for polymer electrolyte membrane fuel cells (PEMFCs). Fluorine-containing polyimide (FPI), end-capped with alkynyl, is synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)- 4,4′-diaminobiphenyl (TFMB), and 3-aminophenylacetylene (APA). The chemical structure of FPI is characterized by ¹H-NMR. The reinforced composite membrane based-on semi-interpenetrating polymer network (semi-IPN) is prepared via solution casting of FPI and Nafion^®212, and crosslinking thereafter. During the membrane preparation, alkynyl in FPI reacts with azide and itself via click chemistry and addition polymerization. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and oxidative stability of the composite membranes are investigated. Compared to Nafion^®212, the composite membrane shows improved thermal stability, mechanical properties, and dimensional stability. The tensile strength of the composite membranes is in the range of 35.0–55.6 MPa, which is much higher than that of Nafion^®212 membrane. The composite membranes show considerable proton conductivity from 2.0 × 10⁻² S cm⁻¹ to 9.9 × 10⁻² S cm⁻¹ at a temperature range from 30 °C to 100 °C, depending on FPI content

[en] Fluorine-containing polyimide (FPI) with hydroxyl groups is synthesized from 4,4′-(hexafluoro isopropylidene) diphthalic anhydride (6FDA), 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP), and 4,4′-diaminodiphenyl ether (ODA) via high temperature polycondensation. Thereafter, alkynyl groups are introduced into FPI. During the preparation of the composite membrane, alkynyl groups on FPI react with azido methyl of 4,4′-bis(azido methyl) biphenyl via click chemistry and form semi-interpenetrating polymer network (semi-IPN) structure within the composite membranes. The mechanical properties, thermal behavior, water uptake, swelling ratio, proton conductivity, oxidative stability, as well as the performance in single cell operation are investigated. Compared to pure perfluorosulfonic acid (PFSA) polymer membrane, the composite membranes based on semi-IPN of FPI and PFSA exhibit improved mechanical properties, excellent thermal and dimensional stabilities, and suitable proton conductivity. The tensile strength of the composite membranes ranges from 28.0 to 67.0 MPa. With increasing FPI content in the membranes, the dimensional stability of the composite membranes increases. The composite membranes have the proton conductivity from 4.3 × 10⁻² S·cm⁻¹ to 1.0 × 10⁻¹ S·cm⁻¹ at 100 °C and also have good performances as proton exchange membrane (PEM) in single cell at 80 °C