Cyclic oligomer chemistry

Abstract

Cyclic oligomers of engineering plastics such as polycarbonate and aromatic polyesters have been known for some time, being formed at very low levels during commercial manufacture. At GE Global Research, we have devised methods for high-yielding and selective preparation of such cyclic oligomers, that are amenable to commercial manufacture. The mixtures of cyclic oligomers have melting points significantly lower than individual ring sizes, and have very low viscosities in the melt. Ring-opening polymerization using appropriate initiators affords rapid reactions (2-6 min) without measurable exotherm, providing very high-molecularweight polymers and without reaction byproducts. These materials have been scaled to commercial quantities, and have shown to be extremely useful for fabrication of glass and carbon fiber composites with high-fiber fractions.

Cyclic polymers: Synthetic strategies and physical properties

“…However, several authors reported that their polymerizations at 250 C (30 min) yielded an equilibrium containing only small amounts (around 1 wt %) of cyclic oligomers, but without presenting compelling evidence for total equilibration. 194,195,199 Other authors presented their polymerizations as kinetically-controlled ROPs despite higher temperatures (up to 340 C). [196][197][198][199][200][201][202][203] For most entropy-driven ROPs, the question of kinetic or thermodynamic control was not discussed.…”

“…206 Most of these ROPs were summarized in recent review articles. 199,203,204 ROPs of cyclic oligomeric bisphenol-A carbonate were most intensively studied. However, several authors reported that their polymerizations at 250 C (30 min) yielded an equilibrium containing only small amounts (around 1 wt %) of cyclic oligomers, but without presenting compelling evidence for total equilibration.…”

“…The driving force is based on a gain in entropy resulting from broadening of the molecular weight distribution and from a gain in segmental mobility. Numerous research groups studied ROPs of aliphatic cyclic oligocarbonates, [189][190][191][192] aromatic cyclic oligocarbonates, [193][194][195] aromatic cyclic oligoesters, 129,[199][200][201][202] aromatic cyclic oligoethers, 203,204 cyclic oligoaramides, 205 and cyclic arylene disulfides. 206 Most of these ROPs were summarized in recent review articles.…”

Poly(hexamethylene terephthalate-co-caprolactone) copolymers: Influence of cycle size on ring-opening polymerization

“…Increasing attention is being paid recently to the utilization of cyclic oligoesters as feedstock for the synthesis and processing of aromatic polyesters [3,[7][8][9]. One source of cyclic oligoesters of great interest is cyclo-depolymerization of linear polyesters, which in combination with ROP, would provide an environmentally friendly route for the chemical recycling of currently important thermoplastics as poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and other closely related industrial aromatic polyesters and copolyesters [10][11][12][13][14].…”

Poly(ethylene‐co‐1,4‐cyclohexylenedimethylene terephthalate) copolyesters obtained by ring opening polymerization

“…A valuable up-dated account of the synthesis and polymerization of cyclic oligoesters has recently been reported by Brunelle. [26] PET is a classical engineering thermoplastic that is produced in huge amounts to be used mainly as fiber and in blowing-injection molding. New tendencies that point toward PET copolyesters with modified properties are able to satisfy new market demands.…”