Norbornene functionalized with fatty acids: Observing the effect of pendant chains on copolymers obtained by metathesis polymerization

Abstract

In this study, fatty acid chains were used to develop functionalized monomers with the aim of reducing dependence on petroleum sources by utilizing plant-based molecules. Pendant groups can influence the physical, physicochemical, and even chemical properties of the polymeric material relative to the non-functionalized counterpart. Thus, norbornene was functionalized with different fatty acids to produce polynorbornene with pendant chains, using acids with varying olefinic unsaturations, as they can be either straight or curved. Bio-substituted fatty-NBEnyl monomers were then obtained from reactions between the carboxylic-norbornene monomer (NBEnyl) and the respective alcohols of stearic (S; C18:0 olefin), oleic (O; C18:1 olefin), or linoleic (L; C18:2 olefin) fatty acids. Individual fatty-NBEnyl monomers and their mixtures in varying amounts were then copolymerized with norbornene (NBE; 80 or 50 wt% as the balance) via ring-opening metathesis polymerization (ROMP), resulting in polymeric materials with pendant fatty chains. All functionalized monomers and copolymers were fully characterized by FTIR and NMR (¹H; ¹³C). Micrographs and rheological behavior of the copolymers differed from that of poly(NBE). While poly(NBE) is porous, the copolymers exhibited smoother surfaces. The copolymers also showed increased linear viscoelastic regions. The effect of bio-substituents on the copolymer properties is discussed.