Cyclic ladder polymers by polycondensation of silylated tetrahydroxy-tetramethylspirobisindane with 1,4-dicyanotetrafluorobenzene

5,5,6,6'-Tetra(trimethylsiloxy)-4,4,4,4'-tetramethyl-1,1-spirobisindane was polycondensed with 1,4-dicyanotetrafluorobenzene under variation of solvent temperature, time, and feed ratio. Under optimized reaction conditions, all products detectable by MALDI-TOF mass spectrometry (up to masses around 8000 Da) proved to be cyclic ladder oligomers and polymers. In N-methylpyrrolidone and dimethylsulfoxide odd-numbered cycles were formed in addition to the prevailing even-numbered ones. However, in sulfolane exclusively even-numbered cycles were obtained (detectable up to masses around 10000 Da), together with even-numbered linear chains. Temperatures above 100 degrees C enhanced the molecular weights by side reactions. With the less reactive cyano-2,3,5,6-tetrafluorobenzene (CTB) again cycles were formed, but their content and the conversions were lower. Polycondensation of CTB up to 160 degrees C and all polycondensations of cyanopentafluorobenzene gave cross-linked products.