Michael A. R. Meier

Plant oil renewable resources as green alternatives in polymer science

The utilization of plant oil renewable resources as raw materials for monomers and polymers is discussed and reviewed. In an age of increasing oil prices, global warming and other environmental problems (e.g. waste) the change from fossil feedstock to renewable resources can considerably contribute to a sustainable development in the future. Especially plant derived fats and oils bear a large potential for the substitution of currently used petrochemicals, since monomers, fine chemicals and polymers can be derived from these resources in a straightforward fashion. The synthesis of monomers as well as polymers from plant fats and oils has already found some industrial application and recent developments in this field offer promising new opportunities, as is shown within this contribution. (138 references.)

Oils and Fats as Renewable Raw Materials in Chemistry

Oils and fats of vegetable and animal origin have been the most important renewable feedstock of the chemical industry in the past and in the present. A tremendous geographical and feedstock shift of oleochemical production has taken place from North America and Europe to southeast Asia and from tallow to palm oil. It will be important to introduce and to cultivate more and new oil plants containing fatty acids with interesting and desired properties for chemical utilization while simultaneously increasing the agricultural biodiversity. The problem of the industrial utilization of food plant oils has become more urgent with the development of the global biodiesel production. The remarkable advances made during the last decade in organic synthesis, catalysis, and biotechnology using plant oils and the basic oleochemicals derived from them will be reported, including, for example, ω-functionalization of fatty acids containing internal double bonds, application of the olefin metathesis reaction, and de novo synthesis of fatty acids from abundantly available renewable carbon sources.

Introducing Multicomponent Reactions to Polymer Science: Passerini Reactions of Renewable Monomers

Combination of the Passerini three component-reaction (3CR) and olefin metathesis led to the formation of poly[1-(alkyl carbamoyl)alkyl alkanoates], a new class of polyesters with amide moieties in their side chain, from renewable resources. Two different approaches were studied and compared to each other. First, monomers were synthesized by the Passerini-3CR and then polymerized via acyclic diene metathesis. Alternatively, bifunctional monomers were synthesized by self-metathesis and then polymerized by Passerini-3CR. Both approaches led to the formation of high-molecular-weight polymers. Moreover, Passerini-3CRs were shown to be a versatile grafting-onto method. The results clearly demonstrate that the Passerini-3CR offers an interesting new access to monomers and polymers and thus broadens the synthetic portfolio of polymer science.

Fatty Acid Derived Monomers and Related Polymers Via Thiol-ene (Click) Additions

Thiol-ene additions of methyl 10-undecenoate, a castor oil derived renewable platform chemical, were studied with the goal of preparing a set of renewable monomers. Good to excellent yields were obtained for these solvent and initiator free thiol-ene additions. The resulting monomers were then polymerized using TBD as a catalyst, to linear as well as hyperbranched polyesters that also contain thio-ether linkages. All thus prepared polymers were fully characterized (NMR, GPC, DSC, and TGA) and the results of these investigations will be discussed within this contribution. The thermal analysis of these polymers revealed melting points in the range from 50 to 71 °C. Moreover, no significant weight loss was observed below 300 °C.

Cross-metathesis of fatty acid derivatives with methyl acrylate: renewable raw materials for the chemical industry

The cross-metathesis of fatty acid esters derived from plant oils as renewable raw materials with methyl acrylate was studied, revealing high conversions for the synthesis of α,ω-dicarboxylic acid esters, depending on the choice of catalyst. A series of unsaturated α,ω-diesters (1,8-, 1,11-, 1,12-, 1,15-, and 1,20-), as well as unsaturated α-esters, was thus prepared and fully characterized. The obtained results can significantly contribute to a sustainable supply of monomers for polyester and polyamide synthesis, as well as for detergents.

Sustainable routes to polyurethane precursors

Environmentally friendly products and procedures are being developed both in industry and academia, mainly due to the depletion of fossil resources and the growing global awareness of the need to protect the environment. Thus, since polyurethanes represent a highly demanded class of polymers, straightforward, isocyanate and phosgene-free methods are required for the synthesis of their precursors (monomers) in order to achieve a sustainable production. To foster the discussion with the final goal to meet such a sustainable production, this review provides an overview of classic as well as modern and more sustainable routes towards polyurethanes and their precursors.

Sequence Control in Polymer Chemistry through the Passerini Three-Component Reaction†

A new strategy to achieve sequence control in polymer chemistry based on the iterative application of the versatile Passerini three-component reaction (P-3CR) in combination with efficient thiol-ene addition reactions is introduced. First, stearic acid was used as a starting substrate to build up a sequence-defined tetramer with a molecular weight of 1.6 kDa. Using an acid-functionalized PEG allowed for an easier isolation of the sequence-defined macromolecules by simple precipitation and led to a sequence-defined pentamer in a block-copolymer architecture. Importantly, this new strategy completely avoids protecting group chemistry. By following this strategy, a different side chain can be introduced to the polymer/oligomer backbone in a simple way and at a defined position within the macromolecule.

Acyclic diene metathesis with a monomer from renewable resources: control of molecular weight and one-step preparation of block copolymers.

The preparation of a long-chain aliphatic alpha,omega-diene from plant oil derivatives and its subsequent polymerization through acyclic diene metathesis (ADMET) is described. The ADMET bulk polymerization of the thus-obtained monomer, undecyl undecenoate, was investigated and optimized by applying ruthenium-based metathesis catalysts from Grubbs and Hoveyda-Grubbs, leading to high-molecular-weight polyesters. Moreover, by applying different amounts of methyl 10-undecenoate as a chain stopper in this ADMET step growth polymerization, the molecular weight of the resulting polyester could be tuned in a range from approximately 10 to 45 kDa. Finally, the application of a poly(ethylene glycol) methyl ether acrylate as the chain stopper led to the preparation of ABA triblock copolymers in a one-step, one-pot procedure.

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).

Use of a Renewable and Degradable Monomer to Study the Temperature-Dependent Olefin Isomerization during ADMET Polymerizations

A detailed study of temperature, catalyst, and polymerization condition dependent isomerization side reactions occurring during ADMET polymerizations revealed important parameters for the design of defined polymers via this technique.