Multicyclic Poly(ether sulfone)s of Phloroglucinol Forming Branched and Cross-Linked Architectures

K2CO3-promoted polycondensations of phloroglucinol and 4,4‘-difluorodiphenyl sulfone (DFDPS) in DMSO yielded mixtures of linear oligomers due to numerous side reactions. In contrast, polycondensations of silylated phloroglucinol under similar conditions were not plagued by such side reactions but involved various cyclization reactions with high efficiency. The MALDI−TOF mass spectra revealed the formation of various cyclic, bicyclic, and multicyclic species of complex structure up to 12 000 Da. Therefore, cross-linking only occurred when a large excess (+30 mol %) of DFDPS was added. The resulting branched and cross-linked polymers mainly consisted of cyclic building blocks. Attempts to introduce sulfonic acid groups by alkylation of pendant OH groups with sultones gave only a moderate degree of substitution, due to the high degree of cyclization. For comparison two polycondensations of silylated 5-methylresorcinol were studied.