9.1 Introduction

Cyclomer technology, ring-opening polymerization (ROP) of cyclic oligomers, has received increasing attention ^[1] since the pioneering work on the synthesis of cyclic carbonates by Brunelle et al. at GE. ^{[2] [7]} This technology is also of current research interest in the high performance polymers area and significant advances have been made. ^{[8] [12]} In general, cyclomer technology has the advantage of avoiding the problem of extremely high melt viscosity associated with high molecular weight linear polymers since cyclic oligomers have much lower melt viscosities. ^[13] ROP of cyclic oligomers provides high molecular weight polymers in a short time without the evolution of low molecular weight volatile byproducts. This feature potentially enables the manufacture of high-performance composites free of voids and residual stress. Additionally, cyclomer technoloy provides opportunities for polymer chemists to tailor the final products by varying the amount and type of suitable cyclic oligomers for specific applications.

This chapter describes the synthesis, characterization, and ROP of cyclic(arylene ether) and cyclic(arylene thioether) oligomers. Cyclic arylates ^{[14] , [15]} and cyclic aramides ^{[16] , [17]} are not dealt with here and interested readers are referred to the original refrences.