Poly(hexamethylene terephthalate-co-caprolactone) Copolyesters Obtained by Ring-Opening Polymerization

Abstract

A set of aromatic-aliphatic copolyesters were synthesized by ring-opening polymerization of hexamethylene terephthalate (HT) cyclic oligomers and -caprolactone monomer (CL) at 175 °C using Sb 2 O 3 catalyst. A hexamer-and heptamer-enriched cyclic fraction isolated from the product obtained in the cyclodepolymerization of poly(hexamethylene terephthalate) (PHT) was used. Ring-opening copolymerizations were conducted for HT to CL feed ratios covering the whole range of compositions and for increasing periods of reaction time. The comonomer contents of the resulting copolyesters were similar to those of their respective feeds, and did not vary with reaction time. In contrast, the copolyester microstructure evolved from block to random as the reaction progressed. The thermal properties of the copolyesters was apparently dependent on both composition and microstructure, and therefore changed with reaction time. The hydrolysis of the copolyesters in simulated physiological medium with and without addition of lipase was evaluated. Copolyesters containing more than 10% of CL were readily degraded in the presence of the enzyme. In contrast to PHT and other copolyesters with lower CL contents, the 50/50 copolyester also underwent extensive hydrolysis upon incubation at pH 10.2 and 80 °C.

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

“…As a consequence, ROP is starting to be considered a serious alternative to the traditional polycondensation method for the preparation of the most-extensively used aromatic polyesters. The ROP method has been successfully extended to the synthesis of copolyesters made up of aromatic and aliphatic units as PET with lactones [21,22] and lactides, [23] poly(butylene terephthalate-co-caprolactone), [24] and poly(hexamethylene-co-caprolactone) [25] prepared from ecaprolactone and cyclic oligomers of butylene terephthalate and hexamethylene terephthalate, respectively. A valuable up-dated account of the synthesis and polymerization of cyclic oligoesters has recently been reported by Brunelle.…”

Hydrolyzable Aromatic Copolyesters of p-Dioxanone

“…The ring-opening copolymerization reaction between c(HT) [2][3][4][5] and DO catalyzed by DBTO is depicted in Scheme 1.…”

“…PHT was synthesized by polycondensation of DMT with HD using TBT as catalyst according to the method previously reported by us. 4 The number-average molecular weight (M n ) and polydispersity index (PDI) measured by GPC were 10400 g · mol -1 and 2.1, respectively. Cyclodepolymerization of PHT was carried out by refluxing a suspension of finely powdered polymer (3.7 g previously dried overnight in a vacuum oven at 60°C) in DCB (200 mL) containing 112 mg of DBTO.…”

“…Once the solid was discarded, the clean solution was evaporated to dryness to afford an oligomer fraction enriched in cycle sizes ranging from 2 to 5 (1.75 g, 47% w/w). This fraction c(HT) [2][3][4][5] …”

“…[21][22][23][24] In our preceding works on this subject, fractions of cyclic oligo(hexamethylene terephthalate)s differing in the average ring size were prepared and copolymerized with ε-caprolactone to obtain copolyesters with composition and microstructure essentially unaffected by cycle size. 4,25 In this work we are using a cyclic HT fraction composed of two-to five-membered rings; the ROP of these cycles can be carried out at temperatures notably lower than those required for carrying out conventional polycondensation minimizing, therefore, the depolymerization of PDO, which is known to begin above its melting temperature.…”