Macrocyclic arylene ether ether sulfide oligomers: New intermediates for the synthesis of high-performance poly(arylene ether ether sulfide)s

A convenient and efficient synthetic route to a new class of macrocyclic aryl ether ether sulfide oligomers is described. This new class of cyclic oligomers is prepared, in excellent yield, by quantitative chemical reduction of macrocyclic aryl ether ether sulfoxide oligomers with oxalyl chloride and tetrabutylammonium iodide. The cyclic sulfoxide oligomeric precursors are prepared in high yield by an aromatic nucleophilic substitution reaction from bis(4-fluorophenyl) sulfoxide and potassium salts of bisphenols under high-dilution conditions. These novel cyclic oligomers were characterized by a combination of GPC, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF-MS), and thermal analyses. The cyclic nature of these oligomers was confirmed by NMR and MALDI-TOF-MS analyses of cyclic sulfoxide oligomers 4a and its linear oligomers 6 and 7. The cyclic sulfoxide oligomers are amorphous with T(g)s varying from 140 to 199 degrees C. Upon chemical reduction, the corresponding sulfide oligomers are highly crystalline with T-m varying from 237 to 350 degrees C. The quantitative reduction of the cyclic sulfoxide oligomers to cyclic sulfide oligomers was confirmed by NMR and MALDI-TOF-MS analyses of sulfoxide 4c and its corresponding sulfide 5c. Ring-opening polymerization (ROP) of the cyclic aryl ether ether sulfide oligomers to corresponding high molecular weight linear polymers can be effected in the melt phase with the addition of a catalytic amount of 2,2'-dithiobis-(benzothiazole) (DTB) disulfide. A tough semicrystalline polymer obtained from ROP of 5a has a T-g of 150 degrees C and T-m of 313 degrees C.