Abstract
Microwave heating holds all the aces regarding development of effective and environment-friendly methods to perform chemical transformations. Coupling the benefits of microwave-enhanced chemistry with highly reliable copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry paves the way for a rapid and efficient synthesis procedure to afford high-performance thermoplastic materials. We describe herein fast and high-yielding synthesis of 1,2,3-triazole functionalized polysulfone through microwave-assisted CuAAC as well as explore their potential as phosphoric acid doped polymer electrolyte membranes (PEM) for high temperature PEM fuel cells. Polymers with various degrees of substitution of the side-chain functionality of 1,4-substituted 1,2,3-triazole with alkyl and aryl pendant structures are prepared by sequential chloromethylation, azidation and microwave-assisted CuAAC using a range of alkynes (1-pentyne, 1-nonyne and phenylacetylene). The completeness of reaction at each step as well as the purity of the clicked polymers were confirmed by 1 H-13 C NMR, DOSY-NMR and FTIR-ATR spectroscopies. The thermal and thermo-chemical properties of the modified polymers were characterized by differential scanning calorimetry and thermogravimetric analysis coupled with mass spec-troscopy (TG-MS) respectively. TG-MS analysis demonstrated that the commencement of the thermal degradation takes place with the decomposition of the triazole ring while its substituents have critical influence on the initiation temperature. Polysulfone functionalized with 4-phenyl-1,2,3-triazole demonstrate significantly higher Tg, Td and elastic modulus than the ones bearing 4-propyl-1,2,3-triazole and 4-heptyl-1,2,3-triazole groups. After doping with phosphoric acid, the functional-ized polymers with ADL of 5 show promising performance with high proton conductivity in anhydrous conditions (in the range of 27-35 mS/cm) and satisfactorily high elastic modulus (in the range of 332-349 MPa).