Stéphane Carlotti

From Lignin‐derived Aromatic Compounds to Novel Biobased Polymers

Nowadays, the synthesis of (semi)aromatic polymers from lignin derivatives is of major interest, as aromatic compounds are key intermediates in the manufacture of polymers and lignin is the main source of aromatic biobased substrates. Phenols with a variety of chemical structures can be obtained from lignin deconstruction; among them, vanillin and ferulic acid are the main ones. Depending on the phenol substrates, different chemical modifications and polymerization pathways are developed, leading to (semi)aromatic polymers covering a wide range of thermomechanical properties. This review discusses the synthesis and properties of thermosets (vinyl ester resins, cyanate ester, epoxy, and benzoxazine resins) and thermoplastic polymers (polyesters, polyanhydrides, Schiff base polymers, polyacetals, polyoxalates, polycarbonates, acrylate polymers) prepared from vanillin, ferulic acid, guaiacol, syringaldehyde, or 4-hydroxybenzoic acid.

Synthesis of glycerin carbonate-based intermediates using thiol–ene chemistry and isocyanate free polyhydroxyurethanes therefrom

A new synthesis of 4-[(prop-2-en-1-yloxy)methyl]-1,3-dioxolan-2-one (AGC) was performed by Williamson ether synthesis from 4-(hydroxymethyl)-1,3-dioxolan-2-one. Dicyclocarbonates were synthesized by UV thiol–ene coupling of allyl-cyclocarbonate with a 2,2′-oxydiethanethiol. This photochemical thiol–ene reaction was carried out under air, with neither solvent nor photoinitiator. The products, obtained with high yield, were characterized by 1H NMR and FTIR analysis. The synthesized dicyclocarbonates were used without purification to synthesize polyhydroxyurethanes without isocyanate by step growth polyaddition with 1,10-diaminodecane. The synthesized polyhydroxyurethanes were characterized by 1H NMR, FTIR, ATG and DSC analysis. These polyhydroxyurethanes exhibited glass transition temperatures from −31 °C to −14 °C, molecular weight from 7,000 g mol−1 to 9000 g mol−1 and degradation temperature for 5% of weight loss (Td 5%) between 227 °C and 250 °C.

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.

Rosin acid oligomers as precursors of DGEBA-free epoxy resins

Rosin acid oligomers were modified and utilized in order to prepare thermosets based on epoxy resins. Epoxide groups were incorporated into this acidic precursor by various synthetic strategies and the corresponding thermosets were obtained thanks to an amino curing agent. Endocyclic epoxidized materials were firstly prepared and used as an additive to diglycidyl ether of bisphenol A (DGEBA) in the presence of isophorone diamine. In a second approach, glycidyl esters of rosin acid oligomers were synthesized and thus utilized for the preparation of DGEBA-free thermosets. Some thermo-mechanical properties of the resulting epoxy resins were explored by DSC and DMA analytical techniques.

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.

Combination of phosphazene base and triisobutylaluminum for the rapid synthesis of polyhydroxy telechelic poly(propylene oxide)

Anionic ring-opening polymerization of propylene oxide, initiated with protonated phosphazene alkoxides and based on monomer activation with a Lewis acid, is investigated. Alcohols bearing one or several protected hydroxyl groups, namely 1,2-isopropylideneglycerol, 1,2:3,4-di-O-isopropylidene-D-galactopyranose and poly(propylene glycol), are firstly deprotonated with a phosphazene base. Their combination with triisobutylaluminum enables quantitative and controlled synthesis of poly(propylene oxide) in a very short time (hours), at room temperature and in hydrocarbons. The chain-ends determination showed a main population initiated by the protonated phosphazene alkoxide. A population coming from the residual transfer to monomer is also observed but in very low intensity. Molar masses of 80 000 g mol−1 with relatively narrow dispersity could be prepared. After deprotection of protected hydroxyl functions, tri- and penta-hydroxy telechelic poly(propylene oxide) were obtained. Dihydroxy telechelic polymers of high molar masses are also rapidly and directly synthesized from poly(propylene glycol).

Epoxidized rosin acids as co-precursors for epoxy resins

A series of novel epoxy resins were prepared from chemically modified rosin, mainly constituted of abietic acid, diglycidyl ether of bisphenol-A (DGEBA) in different percentages as co-reactants, and isophorone diamine as cross-linking agent. Reactive epoxide groups were introduced in the structure of this common pine tree derivative. The chemical structures of various epoxidized rosin acids precursors were confirmed by NMR spectroscopy. Differential scanning calorimetry and dynamic mechanical analysis were used to determine the glass transition temperature and the elastic modulus of the cured epoxy resins. Relatively rigid materials with thermo-mechanical properties depending on the structure of rosin acid derivatives and their ratios with DGEBA were obtained. Epoxy precursors based on renewable rosin can be efficiently used as co-additives of DGEBA for epoxy products.

Activated anionic ring-opening polymerization for the synthesis of reversibly cross-linkable poly(propylene oxide) based on furan/maleimide chemistry

The synthesis of cross-linkable random copolyethers of propylene oxide (PO) and furfuryl glycidyl ether (FGE) is first discussed. The anionic ring-opening polymerization and monomer activation methodology, based on the combination of tetraoctylammonium bromide and triisobutylaluminum, is used to perform the controlled synthesis of poly(propylene oxide-co-furfuryl glycidyl ether) copolymers with various compositions 95/5, 90/10, 75/25, 50/50, and 25/75 (PO/FGE mol%) and keeping the furfuryl moieties active. Copolymers with molar masses around 10000 g mol−1 were obtained in short times. Subsequently, the furfuryl moieties were reacted with aromatic and aliphatic maleimide-based cross-linkers to perform Diels–Alder (DA) “click” reactions. Three-dimensional networks were obtained and their swelling ratio and insoluble fraction were determined. Glass transition temperature and retro-Diels–Alder (rDA) transition in the network were determined by differential scanning calorimetry analyses. Gel properties vary with the furan group amount in the initial copolymer and the cross-linker structure. The network disassembly at 110 °C was monitored by 1H NMR and quantitatively recorded by the re-appearance of the copolymer signals due to the rDA reaction. The solubility study showed that the gel was able to reform at 20 °C leading to reversible cross-linked polyethers.

Rapid and controlled synthesis of hydrophobic polyethers by monomer activation

A series of polyethers was prepared by monomer-activated anionic polymerization. The combination of an ammonium salt with triisobutylaluminum allowed the polymerization of epoxides containing various aliphatic side chains (1,2-butene oxide (BO), 1,2-hexene oxide (HO), and 1,2-octadecene oxide (ODO)) or a fluorinated group (3,3,3-trifluoro-1,2-epoxypropane (TFEP)). Polymers of molar masses up to 35 000 g/mol with relatively narrow molar mass distribution could be synthesized. Polymer structures were analyzed by 13C NMR, and the thermal behavior was studied by differential scanning calorimetry (DSC). The evolution of hydrophobicity was investigated according to the length and composition of the side chain. Using a long aliphatic side-chain epoxide (C16) imparted crystallinity to the resulting atactic polymer.

Retarded Anionic Polymerization of Styrene, 6. Influence of Zinc and Boron Derivatives on the Reactivity of Polystyryllithium

Zinc and boron derivatives were used as additives for the retardation of styrene polymerization initiated by sec-butyllithium. The formation of mixed complexes between polystyryllithium (PSLi) and alkyl zinc or boron derivatives as well as a transmetallation reaction between PSLi and alkoxyborane was studied by UV-vis spectroscopy. Kinetic studies performed in the presence of the additives show that the rate of polymerization is divided only by two with diethylzinc at [Zn]/[Li] = 8 suggesting the contribution of remaining non-complexed PSLi. On the contrary, the rate was found to decrease noticeably with triethylborane upon increasing the [B]/[PSLi] ratio, in agreement with the formation, at 20°C, of ate complexes more stable than than with diethylzinc. However, the dissociation constant of the complexation equilibrium between R 3 B and PSLi is higlhy dependent on the temperature, and the retardation is not so effective at T>100°C. The same retardation effect was observed with borane alkoxides. Transmetallation reaction involving PSLi and B-OR bonds is first observed yielding B(PS) x derivatives. Retardation is governed by the concentration of the remaining PSLi species.