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 (TTSBI) was polycondensed with 1,4-dicyanotetrafluorobenzene (DCTB) 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 8 000 Da) proved to be cyclic ladder oligomers and polymers. In N-methylpyrrolidone and dimethylsulfoxide oddnumbered 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 10 000 Da), together with even-numbered linear chains. Temperatures above 100°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°C and all polycondensations of cyanopentafluorobenzene gave crosslinked products.
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