ABSTRACT
Aromaticpolyethers,suchaspoly(ethersulfone)s,poly(etherketone)sand poly(benzonitrileether)s,areknowntobeexcellenthigh-performanceengineering plastics[1-4].Amongthenumerousdesirableproperties,highthermostability, lowsensitivitytohydrolysisandlowflammabilityareparticularlynoteworthy. Thestructuresofthesepolymersareusuallydescribedintermsoflinearpolymers.However,synthesesofcyclicoligomersviathepseudo-high-dilution methodhavebeenreportedbyseveralauthors[5-32].IncontinuationofcalculationspublishedthreedecadesagobySteptoandco-workers[33,34]andGordon andTemple[35]wehaverecentlypresentedanewtheoryofkinetically-controlledpolycondensations(KCPs)[36].TheKCPmeansthatequilibrationreactions areabsentandthemainproduct istheresultofthemostrapidreaction.Thisnew theorypostulatesthatcyclizationcompeteswithchaingrowthateveryconcentration(eveninbulk)andateverystageoftheprocess,sothat100%cyclesare formedat100%conversion,providedsidereactionsareabsent.Hence,theeffi-
ciency of cyclization is, on the one hand, responsible for limiting the chain growth as illustrated by equation (1) [36, 37], on the other hand, it is an indicator for the completion of a polycondensation. Therefore, we have reinvestigated various syntheses of aromatic polyethers with focus on the optimisation of the reaction conditions and on the formation of cyclic polymers. In the present work we report on syntheses of poly(pyridine ether)s and we review previous studies dealing with poly(ether sulfone)s [38, 39], poly(ether ketone)s [40] and poly(benzonitrile ether)s [41].
