Synthesis of Norbornene Derivatives by Diels-Alder Cycloaddition and Subsequent Copolymerization with Maleic Anhydride

Summary: Several norbornene (Nb) derivatives were synthesized by facile Diels-Alder cycloaddition reactions of cyclopentadiene with α-olefins containing electron-withdrawing groups such as nitrile (CN), phosphonate, and ester. The Diels-Alder adducts were subsequently copolymerized with maleic anhydride (MAH) using free radical polymerization conditions previously determined for MAH/Nb copolymerizations. Further functionality was introduced into the copolymers through acid-catalyzed hydrolysis of poly(Nb-alt-MAH) and poly(NbCN-alt-MAH) copolymers. FTIR confirmed hydrolysis of the anhydrides to carboxylic acid-functionalities and indicated no appreciable hydrolysis of the nitrile functionality. Observed copolymerization rates (kobs) were measured using in situ FTIR. A dramatic decrease in the rate of copolymerization was observed for the Nb derivatives that contained a strong electron-withdrawing functionality. This observation suggested a significant electronic influence on the free radical copolymerization rate with maleic anhydride due to the electron-withdrawing nature of the Nb substituents. Vinylene region of in situ FTIR “waterfall” plot for 50/50 Nb/MAH alternating copolymerization.