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.

Durability of sulfonated aromatic polymers for proton-exchange-membrane fuel cells

As a key component of proton-exchange-membrane fuel cells (PEMFCs), proton-exchange membranes (PEMs) must continuously withstand very harsh environments during long-term fuel cell operations. With the coming commercialization of PEMFCs, investigations into the durability and degradation of PEMs are becoming more and more urgent and interesting. Herein, various recent attempts and achievements to improve the durability of sulfonated aromatic polymers (SAPs) are reviewed and some further developments are predicted. Extensive investigations into inexpensive SAPs as alternative electrolyte membranes include modification of available polymer materials; design, synthesis, and optimization of new macromolecules; durability testing; and exploring the degradation mechanisms.