Poly(arylene ether sulfone)s with different positions of pyridyl groups: Synthesis of the basic diphenyl sulfone dihalide monomers in lithiation and the optimal polymerization in condensation

Abstract

The present study consists of three parts: 1) synthesis of diphenyl sulfone dihalide monomers with different positions of pyridyl groups; 2) fundamental understanding of polymer chain growth (i.e., condensation) and scission (i.e., trans-etherification) involving use of the novel dihalides; and 3) general properties of the basic polymers prepared. The dihalides are 4,4′-difluorodiphenyl sulfone contained with pyridyl groups where the nitrogen atom is in either ortho- or para-position to the ketone bridges, synthesized via lithiation using n-butyl lithium and the corresponding electrophiles. Both dihalides were found to be thermally stable up to 250 °C and their melting points were 222 and 206 °C, respectively. Their versatilities for K2CO3-mediated poly-condensation were confirmed with a careful control of reaction time, temperatures and solvents to depress trans-etherification and cross-linking reactions with an activation energy sufficiently for polymer chain growth. Consequently, the optimal conditions were 130 °C for 24 h in dimethylacetamide that resulted in polymer products with high molecular weights (Mw) ranging from 40 to 200 kDa. The glass transition points of poly(arylene ether sufone)s (PAESs) with pyridyl groups in the para-positions were higher than those of PAESs with pyridyl groups in the ortho-positions under a given Mw, and the thermal decomposition points were higher for PAESs in the ortho-positions than in the para-positions under a given degree of pyridyl substitution. These findings would consequently open up many synthetic routes towards various kinds of monomers and polymers via metalation and condensation reaction schemes.