Effect of gamma irradiation on the structure and properties of sulfonated styrene–butyl acrylate ionic membranes
摘要
The comparative evaluation of gamma-irradiated styrene–co–butyl acrylate (StBuA) membranes sulfonated with sulfuric acid (StBuA–S) or acetyl sulfate (StBuA–AcS) is reported. Copolymers were synthesized by free radical mass copolymerization (80:20 molar ratio) and sulfonated under electrophilic conditions during 5 h and using 100% acid relative to aromatic rings. Membranes were prepared by the doctor blade technique using a THF/DMSO solvent system and subsequently irradiated at 50 kGy. FTIR, DSC and ion exchange conductivity (IEC) analyses revealed that irradiation did not significantly alter the chemical structure but induced partial crosslinking through sulfonic groups, resulting in a marked decrease in IEC—from 1.98 to 0.30 meq·g⁻1 for StBuA–S and from 1.83 to 0.07 meq·g⁻1 for StBuA–AcS. Complex moduli are reduced after sulfonation and partially compensated by irradiation, particularly for AcS sulfonated membranes. SEM micrographs showed that StBuA–S membranes developed extensive porosity and gel domains, while StBuA–AcS exhibited a more compact and uniform morphology, indicating superior structural stability under irradiation. These findings demonstrate that gamma irradiation promotes sulfonic crosslinking responsible for IEC reduction, while the AcS sulfonation route provides enhanced morphological integrity, suggesting its potential advantage in the design of radiation-tolerant polyelectrolytic membranes.