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

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.