Supramolecular thermoplastic elastomers based on charged triblock copolymers

A new type of supramolecular thermoplastic elastomer is reported, consisting of oppositely charged oligomeric ABA-type triblock copolymers with an uncharged hydrophobic middle block and charged outer segments. The polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using a bifunctional chain transfer agent. Separately these polymers behave as viscous liquids, but when mixed together a supramolecular network is formed through electrostatic interaction between the oppositely charged segments. The charged blocks are phase-separated from the uncharged block in a cylindrical structure that was observed by Transmission Electron Microscopy (TEM). Thermal and mechanical analysis of the material using Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and rheology shows that the charged sections have a glass transition temperature (Tg) close to room temperature, but that the material has elastomeric properties at temperatures far above this Tg.