Synthesis of Poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)]‐Poly(propylene oxide) Block Copolyester by Direct Polyesterification of Reactive Oligomers

Abstract

Summary: The objective of this study was to synthesize thermoplastic elastomers by the direct copolyesterification of reactive oligomers of poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] (PET) and poly(propylene oxide) (PPO). The synthesis of hard segment oligomers was achieved in two steps. The first step consisted of the glycolysis of PET leading to α,ω‐hydroxyl functionalized oligomers. The second step corresponded to the ring opening polymerization of ε‐caprolactone onto the hydroxyl end groups of the PET oligomers. Commercially available hydroxytelechelic poly(propylene oxide) was modified to obtain carboxytelechelic poly(propylene oxide). The chemical structure of the product was investigated by 1H NMR and size exclusion chromatography (SEC). Multiblock poly(ester‐ether) was then synthesized by polyesterification of hydroxytelechelic poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] with carboxytelechelic poly(propylene oxide) oligomers, using different catalysts and reaction conditions. The best stoichiometric ratio for the reaction was determined in order to obtain the highest possible $\overline M _{\rm n}$. The chemical structure of the synthesized poly(ester‐ether) was investigated by size exclusion chromatography and 1H NMR. The thermal and thermomechanical behavior of the synthesized poly(ester‐ether) was investigated by differential scanning calorimetry and dynamic mechanical analysis, which showed that the poly(ester‐ether) behaved as a thermoplastic elastomer. This product could also be an interesting way for chemical recycling of PET waste.Synthesis of multiblock co‐poly(ester‐ether).magnified imageSynthesis of multiblock co‐poly(ester‐ether).

Thermoset Elastomers Derived from Carvomenthide

“…Taken together, all data related to the molar mass obtained by the one-pot, two-step method indicated that the postpolymerization functionalization did not induce adverse side reactions leading to cleavage or cross-linking of polymer chains. In sum, this simple method for the preparation of α,ω-carboxy-terminated poly(lactone) using succinic anhydride was a new attempt to make a renewable secondary hydroxyl-terminated poly(lactone), going beyond previously reported synthetic protocols regarding petroleum-based primary hydroxyl group-containing polyols. − , …”

“…1 Synthesis of Carboxy-Telechelic Poly(carvomenthide) (HOOC-PCM-COOH). The general procedure to prepare the carboxy-telechelic PCM via postpolymerization functionalization was as follows: 25 The hydroxyl-telechelic PCM (1 equiv based on two endhydroxyl groups) was introduced into a pressure vessel (350 mL) with a magnetic stir bar. 1,4-Dioxane was added to the vessel, and the mixture was stirred to completely dissolve the polymer at room temperature for 30 min.…”

“…The secondary hydroxyl terminal groups of the PCM samples were converted to carboxy end groups using succinic anhydride (SA) as a reagent and dimethylaminopyridine (DMAP) as a catalyst via a postpolymerization functionalization, designated as HOOC-PCM-COOH(3), HOOC-PCM-COOH( 6), and HOOC-PCM-COOH(12). 24,25 Upon completion of the reaction, the resonance of the terminal methine proton (H a ) of the hydroxyl-terminated PCM at δ 3.76 ppm disappeared, and a new signal for the two terminal methylene protons of the carboxy-terminated PCM was observed at δ 2.59 ppm in the 1 H NMR spectrum (H e ; Figures 1b,c and S2b,c) with high levels of coupling (>99% conversion). HOOC-PCM-COOH(3), when compared to that of HO-PCM-OH(3) (Figure S2d), also exhibited new resonances in the 13 C NMR spectrum at δ 176.3 (C1), 171.6 (C3), 71.4 (C4), and 28.8 (C8) ppm, corresponding to the carbonyl groups, methine carbon, and methylene carbons of the terminal carboxy group (Figure 1d).…”

“…23 The direct polyesterification of hydroxyl-telechelic poly(ethylene terephthalate) (PET) with carboxy-terminated PCL (F = 1.98) or carboxy-ended poly(propylene oxide) (PPO), in which the number of functionality (F) was not determined, was used to synthesize a multiblock poly(ester-ether) exhibiting thermoplastic elastomer properties. 24,25 After the primary hydroxyl end group in poly(tetramethylene oxide) (PTMO) was converted to carboxylic acid with F ∼ 2.0, as estimated by the chemical titration method, the carboxy-ended PTMO was cured with an epoxy resin and pyromellitic dianhydride (PMDA); the resulting material, however, showed no shape memory properties. 26 Poly(glycerol sebacate) (PGS), commercially available as the brand Regenerez, is a tough polyester prepared via polycondensation of glycerol and sebacic acid for soft tissue engineering.…”

Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

“…Saint-Loup and co-workers also used ethylene glycol in reactive extrusion to produce low molecular weight oligomers (1450+1800 g·mol -1 ) without quantification of their yields for synthesis of PET-polycarbonate polyesters. However, these oligomers had to be separated and purified for further processing, since the crude reaction product consisted of a heterogeneous mixture of BHET-analoga [215][216][217][218]. The second most common degrading agent for glycolysis was diethylene glycol.…”