Modification of vegetable oils and their use in photo-"click" chemistry

Making plastic materials from renewable resources is an old practice, as old as the birth of macromolecular science and technology. The vegetable oils are currently the most widespread renewable resources in the chemical industry as they are one of the most important renewable platform chemicals due to their universal availability, inherent biodegradability properties. The most prominent example of click chemistry reaction is based on copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) reaction between azides and terminal alkynes, discovered by the groups of Sharpless and Meldal. The CuAAC click reaction has received attention as powerful modular synthesis approach, which has found numerous applications in supramolecular chemistry, drug discovery, bioconjugation and materials science. However, it has some limitations including the need for a metal catalyst, an inability to control the reaction by external stimulation or to conduct the reaction in the absence of solvent. To eliminate these disadvantages, the required copper (I) catalyst for the CuAAC reaction can be generated by in-situ reduction of Cu(II) to Cu(I) by various reducing agents, photochemical and electrochemical redox processes, and copper-containing nanoparticles. Recently, a new photochemical protocol to catalyze the CuAAC reaction between azides and alkynes by in-situ generation of Cu(I) from Cu(II) complex with UV-light was developed. A simple method based on photochemically induced copper(I)-catalyzed azide-alkyne cycloaddition click reaction (CuAAC) is developed for the preparation of thermoset networks from soybean oils as renewable resources. The incorparation of clickable azide and alkyne functionalities into epoxidized soybean oils are done by simultaneous ring-opening reactions between epoxide group of soybean oils with sodium azide and propargyl alcohol, respectively. The obtained azide- and alkyne-functionalized soybean oils are eaisly transformed cross-linked networks via photoinduced CuAAC reaction at ambient conditions. The additon of multifunctional monomers in the formulation not only increase the cross-linking density but Al-SBO improve the mechanical properties of the obtained thermoset material. In comparison of two formulations, the sample containing additional multifunctional monomers has higher glass transition temperature, storage modulus and damping properties. Key words: Copper-catalyzed azide–alkyne cycloaddition, click chemistry, photoinduced reactions, renewable resources, vegetable oils