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Styrene has been copolymerised with 4,4′-divinylbiphenyl and with 4,4′-diisopropenylbiphenyl in 15% toluene solution at 95°C. The copolymers have been analysed via UV spectroscopy, to give estimates of total crosslinker incorporated and of the number of pendant double bonds remaining. Extrapolation of the results—including viscometry—to zero conversion indicates that both crosslinkers form intramolecular linkages (rings). These rings appear to be comparable in size with those formed with p-divinylbenzene, but to occur rather more frequently. Estimates of copolymerisation reactivity ratios r1 (styrene=1) are, for 4,4′-divinylbiphenyl 0,77, for 4,4′-diisopropenylbiphenyl 1,3. It is concluded that, contrary to a previous suggestion, increasing separation of reactive groups leads to more, not less, intramolecular reaction. |
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