Ring Opening Metathesis Polymerization of Fatty Acid Derived Monomers

Interest in the synthesis of bio-based polymers, especially derived from vegetable oils, has grown significantly due to rising costs and the environmental impact of petroleum based polymers [1]. Fatty acid derived monomers can be polymerized with various polymerization methods. For instance, ring opening metathesis polymerization (ROMP) employing well defined transition metal alkylidene catalysts was shown to be an efficient method to obtain polymers with controlled molecular weights, narrow polydispersities, and various side chain functionalities [2,3]. In the search for high performance polymer architectures, bicyclo[2.2.1]hept-2-ene (known by its trivial name norbornene) and its derivatives have recently been in the centre of interest due to interesting properties of the thereof derived polymers [4].
Herein, we report two synthetic approaches towards polynorbornenes functionalized with fatty acids varying from 6 to 22 carbons. The first approach involves the esterification of a hydroxy-functional norbornene monomer with fatty acids of different chain lengths and their subsequent living ROMP with “Grubbs” 3rd generation catalyst. In the second approach, ROMP has been used to produce well defined functional group containing polymer backbones. Therefore, a hydroxy-functional monomer was first polymerized to the desired molecular weight. This functional polynorbornene precursor polymer was then reacted with fatty acids methyl esters of different chain lengths in a grafting onto approach. All synthesized polymers were characterized by GPC and NMR. Furthermore, the effects of the fatty acid chain length on the polymerization process, and the thermal and mechanical properties of the resulting polymers have been extensively investigated.

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