Dynamic Mechanical Analysis, chain flexibility

There have been studies indicating that blends of PBI polymers with pyridine-containing polymers could prove useful in a high-temperature PEM fuel cell. Kallitsis et al. [31] combined commercially supplied w-PBI with an aromatic polyether that contained a pyridine moiety in the main chain (PPyPO) these polymer blends were then soaked in 85% wt PA. Dynamic mechanical analysis of a 75/25 PBl/PPyPO block copolymer showed reasonable mechanical strength and flexibility. The conductivity of this copolymer was not reported, but the conductivity of 85/15 PBI/PPyPO block copolymer was 0.013 S cm at a relatively low PA doping level. Further investigation of these systems is required to prove its utility as a fuel cell membrane. 

Solid-state properties of the catenane copolymer were determined using DSC and dynamic mechanical analysis (DMA) and were compared with pure PC. DSC revealed a glass transition temperature of ca. 150°C for all the catenane copolymers 22 to 24, which is essentially the same as the pure PC sample of the same molecular weight. This insensitivity of the Jg to the presence of the catenane repeat unit is possibly on account of the considerable flexibility/mobiUty of these catenanes. DMA of the copolymer containing 20% (w/w) catenane showed three transitions at —100, —6, and - -80°C. The first and third transitions are observed in PC films while the —6°C was linked to the catenane ring/chain movements. 

---