Oligomeric A₂ + B₃ synthesis of highly branched polysulfone ionomers: novel candidates for ionic polymer transducers

Highly branched poly(arylene ether sulfone)s with systematically varied degrees of branching andsulfonationwere synthesized through oligomeric A₂ + B₃ methods for application as ionic polymer transducer (IPT) membranes. IPTs area class of electroactive polymer devices that leverage ionomeric membranes to perform electromechanical transduction as actuators and/or sensors. Synthesis of controlled molecular weight A₂ oligomeric polysulfones targeted the global degree of branching (DB_global) to approximately 1-3% in the absence of gelation. Size exclusion chromatography confirmed molecular weights greater than 20 000 g mol^-1 were achieved for linear and branched polysulfones. Increased degree of sulfonation of the A₂ oligomers reduced the development of molecular weight in the oligomeric A₂ + B₃ branching reaction; the formation of tough, flexible, ion-conducting membranes is required for emerging transducer applications. Variation in the DB_global attained did not affect the thermal transitions or elastic modulus as significantly as changes in the degree of sulfonation. However, an ionic dissociation temperature was detected below the glass transition temperature of the polysulfone matrix and was relatively independent of the degree of sulfonation. Successful synthesis and characterization of these well-defined branched polysulfone ionomers provide a basis for future investigation of polymer topology effects on IPT performance.