Novel macrocyclic aryl ether oligomers containing a diphenylacetylene moiety: synthesis, characterization and ring-opening polymerization

An efficient synthetic route to a range of macrocyclic aryl ether ketone and sulfone oligomers containing a cross-linkable diphenylacetylene moiety in the backbone is described. This new class of macrocyclic oligomers, obtained in excellent yield, is prepared by an aromatic nucleophilic substitution reaction from the potassium salt of bis(3-hydroxyphenyl)acetylene and activated difluoro-monomers. Detailed structural characterization of these novel oligomers by the combination of n.m.r. and matrix assisted laser desorption and ionization-time of flight-mass spectroscopy (MALDI-TOF-MS) confirms their cyclic nature; and the compositions of these macrocyclic oligomers are provided by g.p.c. and reverse-phase gradient h.p.l.c. analyses. MALDI-TOF-MS is a unique tool for the determination and the proof of the cyclic nature of random co-cyclic oligomers, and also provides answers to the possible combinations of monomer units in the cyclic oligomeric components for the random co-cyclic oligomers. All macrocyclic oligomers are semicrystalline with Tm varying from 267 to 370°C and when the oligomers are heated an exothermic reaction, resulting from reaction of the acetylene units, occurs in the range of 340-470°C and the macrocyclics undergo a cross-linking reaction. Polymerization of the lower melting macrocyclic oligomers at 280-300°C, in the presence of a nucleophilic initiator, led to the formation of high molecular weight insoluble materials with limited cross-linking reactions taking place. The resulting polymers can be further cross-linked at 340°C with a Tg increase up to 100°C or complete disappearance of Tgs.