Kinetics and Mechanisms of Poly(poly(ethylene terephthalate)-co-poly(ε-caprolactone)) Catalyzed Randomization: Influence of End Groups

Abstract

Hydroxy-ester interchanges were found to be the predominant reactions involved in poly-(ethylene terephthalate)-poly(ε-caprolactone) copolyester randomization. Even for high molar-mass copolyesters having low hydroxyl end group concentration, kinetic studies show that ester-ester interchanges play a minor role. Reaction rate was almost proportional to hydroxyl end groups concentration. The randomization kinetics was studied by 1 H NMR on copolyesters obtained in situ by reacting a series of poly(ethylene terephthalate)s of various molar masses and end groups with ε-caprolactone, in the molten state and in the presence of Ti(OBu) 4 catalyst. A mechanism involving parallel catalyzed second-order hydroxy-ester and ester-ester interchanges is proposed for the randomization step and perfectly fits experimental data. This study clearly shows that the nature and concentration of hydroxyl end groups must be carefully controlled for reliable synthesis of copolyesters by homopolyester melt blending.

Synthesis of novel hyperbranched polymers featuring oxazoline linear units and their application in fast‐drying solvent‐borne coating formulations

“…The dramatic effect of the end‐capping reaction with citronellol upon the branched nature and molecular weight of the HBPs was rationalized by a combination of trans‐esterification and oxazoline ring reformation processes (Scheme ). It is well‐documented that trans‐esterification will occur within chains or esterification at chain ends when polyesters and alcohols are heated in the melt . Therefore, it is not unreasonable to assume that, in this study, the trans‐esterification reaction was in part responsible for the structure change between the HBPs 7a and 7b and the citronellol end‐capped polymers 10a – 11b as a result of the reversible nature of the ester linkages.…”

“…It is well-documented that trans-esterification will occur within chains or esterification at chain ends when polyesters and alcohols are heated in the melt. 34,35 Therefore, it is not unreasonable to assume that, in this study, the trans-esterification reaction was in part responsible for the structure change between the HBPs 7a and 7b and the citronellol end-capped polymers 10a-11b as a result of the reversible nature of the ester linkages. Competitive endcapping reactions of citronellol with ester linkage of the HBPS will result in a redistribution of weight average molecular M w of 10a-11b.…”

Film reaction kinetics for melt postpolycondensation of poly(ethylene terephthalate)

“…Chain growth process of polycondensation mainly depends on the ester exchange reaction and esterification reaction . The combination of mass transfer together with chemical reactions is deeply coupled in polycondensation .…”

“…[3] Chain growth process of polycondensation mainly depends on the ester exchange reaction and esterification reaction. [4] The combination of mass transfer together with chemical reactions is deeply coupled in polycondensation. [3] It is controlled by the polycondensation reaction and the slower steps in the diffusion of by-products formed in the system.…”

Kinetic Monte Carlo Studies on the Importance of the Reaction Scheme in Segmental Exchange of Copolymer Chains

“…Segmental exchange reactions (reshuffling) are common phenomena in ionic and covalent ring opening polymerization of heterocyclic monomers, which often preclude synthesis of (co)polymers with required strictly defined properties. Although there are several reaction routes leading to segmental exchange, the processes involving active chain ends are the most important 1–6. These processes are realized by the attack of an active center of polymerization (or of a specific type of chain end, which is active in segmental exchange processes) on a monomeric unit in another chain and subsequent chain scission of the attacked macromolecule with the simultaneous merging of the attacking chain with one part of the cleaved chain (Scheme ).…”