Copolymers of xylan-derived furfuryl alcohol and natural oligomeric tung oil derivatives

The utilization of vegetable oils as biological oligomers for the synthesis of macromolecular materials has considerably evolved in the last decades, opening the way for the preparation of sophisticated materials based on synthetic processes for the design of polymers with very specific applications. Tung oil (TO), easily obtained from the seeds of the Asian tung tree (Vernicia fordii), is a relatively cheap commodity that has as its main constituent (~85%) a peculiar natural oligomeric triglyceride structure in which each chain bears three conjugated unsaturations corresponding to α-eleostearic acid. Following a previous study based on the association of TO with furans for the preparation of linear and cross-linked structures based on the Diels-Alder click reaction, the present study deals with the cationic (co) polymerization of xylan-derived furfuryl alcohol (FA) with TO, in order to combine the high intrinsic flexibility of the crosslinked TO polymers with the stiffness of the FA resin, which should lead to fully bio-based crosslinked materials with a tunable glass transition. Three approaches were investigated using trifluoroacetic acid (TFA) in chloroform, viz. (i) combining crude TO and furfuryl alcohol, (ii) combining methyl α-eleostearate and furfuryl alcohol, and (iii) polymerizing furfuryl α-eleostearate itself. The polymerization reactions with varying TFA concentrations were followed by ¹H NMR spectroscopy, and it was possible to get valuable information on mechanistic aspects. Also, higher concentrations of TFA were used to synthesize and isolate polymer networks, in order to understand their molecular characteristic as well as access their main thermal properties.

Keywords: Cationic copolymerization; Furfuryl alcohol; Tung oil.