René Saint-Loup

Synthesis of (polyethylene terephthalate/polyϵ-caprolactone) copolyesters

Abstract Polyethylene terephthalate (PET) was alcoholised with ethylene glycol to synthesize hydroxytelechelic oligomers of PET. On the other hand, commercial hydroxytelechelic polyϵ-caprolactone was modified in order to synthesize carboxytelechelic polyϵ-caprolactone. The chemical structure of the products was investigated by 1H NMR. Multiblock copolyesters were then synthesized by polyesterification of hydroxytelechelic PET and carboxytelechelic polyϵ-caprolactone oligomers, using several catalysts and different reaction conditions, which have been linked with the average molecular weight of the obtained block copolyesters. It appeared that residual distannoxane species coming from glycolysis step are best catalyst for polyesterification reaction. The chemical structure of the synthesized copolyesters was investigated by size exclusion chromatography and 1H NMR. The thermal and thermomechanical behavior of the synthesized copolyesters was investigated by differential scanning calorimetry and by dynamic mechanical analyses. The ester–ester interchange reaction between the two types of oligopolyesters has been enlightened and estimated taking in account the different reaction parameters. This side reaction led to the miscibility of the two phases of the oligomers, that can be explained by a random structure of the copolyester, and prevented to obtain multiblock copolymer.

Photochemical induced polymerization of vinylidene fluoride (VDF) with hydrogen peroxide to obtain original telechelic PVDF

Abstract The photochemical induced polymerization of vinylidene fluoride (VDF) with hydrogen peroxide, leading to original telechelic (or α,ω-difunctional) PVDF, is presented. The influence of the nature of the solvents and the [H2O2]0/[VDF]0 initial molar ratios ranging from 4 to 80% was investigated. It was shown that the lower this ratio, the higher the molecular weights of the produced telechelic polymers. 19 F -NMR spectroscopy enabled the degree of polymerization, ( DP n ) , of these fluorinated polymers or oligomers to be assessed. Interestingly, the reversed/normal ratio of VDF units in these fluorocompounds was low. The mechanism of the reaction was investigated and showed that the hydroxyl radical generated from hydrogen peroxide reacted mainly at the hydrogenated carbon atom, but also to the fluorinated site yielding CO2H end-functions. This is discussed.

Synthesis of hydroxytelechelic ε-caprolactone/poly(ethylene terephthalate) co-oligomers, 1

In the presence of ethylene glycol, poly(ethylene terephthalate) (PET) undergoes chain scissions with the formation of α,ω-hydroxyl oligomers, through classical transesterification by alcoholysis. e-Caprolactone was subsequently added on the hydroxyl end groups of PET oligomers by ring-opening polymerization at different molar ratios of e-caprolactone to PET oligomers. The chemical structure of the products was investigated by size exclusion chromatography, 1 H NMR spectroscopy, and differential scanning calorimetry. A large majority of these products are soluble in common organic solvents. The thermal and 1 H NMR analyses reveal that the transesterification between base units of PET oligomers and e-caprolactone during the synthesis is always present whatever the reaction conditions. This phenomenon leads to copolymers having thermal properties different from those of PET. However, some cooligomers present the interest of keeping properties close to those of PET. The main purpose of this study was the synthesis of PET co-oligomers that are soluble in some organic solvents that would make their use easier, and so that they can be used further as hard segment precursers for polycondensation reactions.