Periodically Functionalized and Grafted Copolymers via 1:2-Sequence-Regulated Radical Copolymerization of Naturally Occurring Functional Limonene and Maleimide Derivatives

Naturally occurring hydroxy-functionalized limonene analogues, i.e., monoterpene alcohols such as perillyl alcohol and carveol, were radically copolymerized with cyclohexylmaleimide (CyMI) in PhC(CF3)(2)OH via 1:2-sequence-regulated propagation to obtain periodically functionalized bio-based copolymers possessing one hydroxyl group in every three-monomer unit. Alternatively, a combination of hydroxy-functionalized maleimide (N-2-hydroxyethylmaleimide: HEMI) and limonene resulted in another periodically functionalized copolymer possessing two hydroxyl groups for every three-monomer unit. These copolymerizations were fitted well by the penultimate model, where the hydroxyl functions did not have a significant effect on the selective propagation, as has been reported for a combination of nonfunctionalized limonene and CyMI. The periodic hydroxyl groups can be quantitatively converted into carbamate moieties by a polymer reaction with isocyanate to result in another series of 1:2 and 2:1 periodically functionalized copolymers. Periodically grafted copolymers possessing one or two graft chains repeating in three-monomer units were prepared by radical copolymerization of chlorine-functionalized limonene or maleimide derivatives, which were synthesized from hydroxy-functionalized monomers, followed by ruthenium-catalyzed living radical polymerization of methyl methacrylate initiated from periodically introduced C-Cl bonds in the backbone copolymers.