Etienne Grau

Structure–properties relationship of fatty acid-based thermoplastics as synthetic polymer mimics

Nowadays the use of vegetable oils as polymer precursors is the subject of growing interest in the academic and industrial communities. Many synthetic pathways can be pursued from natural vegetable oils to yield different functionalized derivatives – also called synthons – and polymers, such as polyesters, polyurethanes, polyamides, etc. Herein, we widely overview recent progress in the preparation of vegetable oil-based thermoplastic polymers and, more precisely, thermoplastic polyesters and polyurethanes. Extra focus is also placed on the synthesis sustainability of these polymeric materials via atom efficient techniques, “green” catalyses and processes. The achievable bio-sourced polymers cover a wide range of thermo-mechanical properties that can respond to most of the current applications of synthetic polymers.

Renewable (semi)aromatic polyesters from symmetrical vanillin-based dimers

Two symmetrical biphenyl monomers derived from vanillin, a methylated divanillyl diol and a methylated dimethylvanillate dimer, were synthesized and employed as (co)monomers for the design of renewable (semi)aromatic polyesters. The reactivity in polytransesterification of these new monomers was investigated in bulk in the presence of various catalysts. The polytransesterification between methylated divanillyl diol and a series of bio-based diesters having different chemical structures led to amorphous thermoplastic polyesters with glass transition temperatures ranging from −5 to 139 °C and thermal stability up to 350 °C.

ADMET polymerization of bio-based biphenyl compounds

Four biphenyl monomers derived from vanillin or eugenol were synthesized and polymerized by the ADMET methodology. The biphenyl compounds were produced by enzymatic dimerization of 2-methoxy-4-methylphenol, methyl vanillate, vanillin and eugenol. Further chemical modifications of the obtained dimers such as transesterification, Wittig reaction or allylation led to α,ω-dienes. The reactivity of these bio-based monomers towards ADMET polymerization employing several catalysts was investigated. Only oligomers were obtained when the diallylated compound was employed. The polymers based on dieugenol and the bis-unsaturated diester exhibit good thermal stability and Tg at 17 and 54 °C, respectively. Polymerization of the divinyl compound obtained by the Wittig reaction of divanillin showed a reasonable molar mass of 30 000 g mol−1, a high Tg at around 160 °C and thermostability with a 5% weight loss occurring at 380 °C.

Unexpected dimerization of isoprene in a gas chromatography inlet. A study by gas chromatography/mass spectrometry coupling.

During analysis of pure isoprene by gas chromatography/mass spectrometry (GC-MS) using a programmed temperature vaporization (PTV) inlet, the presence of several isoprene dimers was detected in the total ion chromatograms (TICs). This study intends to determine the part of the instrument where dimerization occurs and the relative importance of the dimer amounts under different experimental conditions. The reference thermal dimerization of isoprene gives four six-membered cyclic dimers and two eight-membered ones. In all samples containing different amounts of freshly distilled isoprene, only peaks corresponding to the former appeared in TICs. For the same temperature, their amounts increase as the concentration of injected isoprene increases. The main products are diprene (from 80 to 100%) of the total dimers and dipentene (from 1 to 14%). The sum of the two other dimers is never higher than 6%. In conclusion, isomeric dimers are produced through a dimerization in the inlet. No dimerization of isoprene occurs in the mass spectrometer source. Then care is needed when analyzing terpenic compounds in the presence of isoprene by GC-MS because structures, retention times and mass spectra of diprene and dipentene are close.