Matthias Winkler

Renewable polycarbonates and polyesters from 1,4-cyclohexadiene

Epoxides derived from 1,4-cyclohexadiene (CHD), the latter produced from renewable resources via self-metathesis of plant oil derivatives, are applied as key substrates in ring-opening copolymerizations to produce aliphatic polycarbonates and polyesters. Renewable, unsaturated polycarbonates are prepared by the ring-opening copolymerization of epoxide/CO2; these are catalysed by di-zinc/magnesium complexes previously reported by Williams et al. or by using chromium(III) or cobalt(III) salen complexes. Renewable, unsaturated polyesters, with glass transition temperatures up to 128 °C, were obtained by the ring-opening copolymerization of epoxide/phthalic anhydride. The relative rates of these copolymerizations were monitored using in situ attenuated total reflectance infra-red (ATR-IR) spectroscopy. The polymers were fully characterized using spectroscopy (nuclear magnetic resonance, infra-red), mass spectrometry (matrix assisted laser desorption ionization), and by thermal methods (differential scanning calorimetry and thermogravimetric analysis).

Olefin cross-metathesis as a valuable tool for the preparation of renewable polyesters and polyamides from unsaturated fatty acid esters and carbamates

Olefin cross-metathesis of unsaturated fatty acid methyl ester (FAME) derived benzyl carbamates with methyl acrylate is described. The obtained by-product, an α,β-unsaturated ester, was further modified via thia-Michael addition reactions in order to synthesize branched AA-type or AB-type monomers for the preparation of polyesters, which are tuneable by oxidation. Cross-metathesis of fatty acid derived carbamates was used as a novel approach to prepare linear AB-type monomers, which can be used for the preparation of renewable polyamides PA11, PA12 and PA15. The necessary fatty acid carbamates were prepared by applying a catalytic Lossen rearrangement procedure. The presented synthesis strategy has potential for the bio-sourced preparation of monomers for the production of polyamides. All prepared polymers were fully characterized by NMR, SEC, and DSC analyses. Additionally, the Youngs modulus of the prepared long-chain polyamide PA15 was determined.

A new approach for modular polymer–polymer conjugations via Heck coupling

Heck coupling reactions are introduced as a modular, very efficient and highly orthogonal method for polymer–polymer conjugation. Several diblock and triblock copolymers (5200 Da ≤ Mn ≤ 17300 Da, 1.08 ≤ PDI ≤ 1.33) were prepared via Heck coupling reactions of acrylate-terminated and aryliodide-terminated polymers. The coupling reactions were performed using the so-called Jefferys conditions, which allowed the use of equimolar amounts of reacting polymers and low reaction temperatures. Acrylated poly(ethylene glycol) monomethyl ether (PEG), poly(e-caprolactone) (PCL) and polymers synthesized via head-to-tail selective acyclic diene metathesis (ADMET) polymerisation have been successfully conjugated with both a PEG and PCL containing an aryliodide moiety.

Highly efficient oxyfunctionalization of unsaturated fatty acid esters: an attractive route for the synthesis of polyamides from renewable resources

An efficient and environmentally benign strategy for the oxyfunctionalization of fatty acid methyl esters (FAMEs) employing molecular oxygen as an oxidizing agent is described. Keto-fatty acid esters were directly synthesized by co-catalyst-free Wacker oxidations employing oxygen as a sole re-oxidant. Amine functionalization of the thus obtained keto-fatty acid esters was achieved by reductive amination. The prepared renewable AB-type monomers were studied in homopolymerizations as well as in copolymerization reactions with hexamethylendimethylamine and dimethyl adipate to modify the properties of conventional Nylon 6,6. The obtained (co)-polymers were characterized by SEC, NMR and DSC analysis as well as water uptake tests.

Acyclic Diene Metathesis Polymerization and Heck Polymer–Polymer Conjugation for the Synthesis of Star‐shaped Block Copolymers

Three- and four-arm star shaped polymers, as well as diblock copolymers, are synthesized via acyclic diene metathesis (ADMET) polymerization. This is accomplished by using an asymmetric α,ω-diene containing a terminal double bond and an acrylate, which is polymerized in the presence of multifunctional acrylates as selective and irreversible chain transfer agents using Hoveyda-Grubbs second generation catalyst. High cross-metathesis selectivities are achieved at low temperatures enabling good control over molecular weights. Furthermore, additional polyethyleneglycol (PEG) blocks are attached to these polymers via Heck coupling of the acrylate end-groups of these polymers with aryl iodide functionalized PEG, obtaining three- and four-arm star shaped di- and triblock copolymers with molecular weights up to 31 kDa.