Temperature dependant double bond isomerization side reactions during ADMET polymerizations studied with a monomer from renewable resources

Acyclic diene metathesis (ADMET) polymerization has developed into a very versatile technique for the preparation of a variety of macromolecular architectures, including linear polymers [1,2], polymers with a defined degree of branching [3], telechelics as well as block-copolymers [4,5]. Recently, the technique was also applied to monomers with a functionality > 2, thus resulting in hyperbranched macromolecules from AB2, AB3, and A3 monomers with B1 chainstoppers, respectively [6,7]. Applying this efficient catalytic process to monomers from renewable resources will lead to the development of materials with interesting properties that have the potential to replace existing fossil oil based materials [8].
Within this contribution, the utilization of plant oils as renewable raw materials for monomers and polymers will be discussed. Therefore, the synthesis of a novel and degradable monomer from fatty acid derivatives will be described and its subsequent ADMET polymerization discussed in detail. We will focus our discussions on the investigation of double-bond isomerization side-reactions occurring during these ADMET polymerizations. Therefore, the resulting polyesters were transesterified with methanol in order to investigate the nature and the amount of isomerization side-reactions that occurred during the polymerizations by GC-MS. These investigations revealed that the Grubbs first generation catalyst does hardly show any side reactions up to a polymerization temperature of 90 °C, whereas the second generation catalyst from Grubbs showed up to 75% isomerisation side reactions depending on temperature as well as other polymerization conditions. This study represents the first quantitative study of isomerisation side reactions during ADMET polymerizations and will therefore help to tailor polymeric architectures prepared via this technique.

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