Free Radical Terpolymerization of Trans‐Anethole, Maleic Anhydride and N‐Ethylmaleimide

Abstract

Trans‐anethole (ANE) and maleic anhydride (MSA) do not homopolymerize in tetrahydrofuran and in chloroform with α,α′‐azoisobutyronitrile (AIBN) as initiator. In comparison, N‐ethylmaleimide (NEMI) is homopolymerized very slowly. From these monomers, three binary systems have been studied and their copolymerization ratios were determined at 60°C: ANE/MSA (r 1=0.002, r 2=0.001 (in THF)), ANE/NEMI (r 1=0.033, r 2=0.284 (in THF) and r 1=0.079, r 2=0.097(in CHCl3)) and MSA/NEMI (r 1=0.158, r 2=1.676 (in THF) and r 1=0.070, r 2=2.677 (in CHCl3)). The terpolymerization of these three monomers results in polymers with more than 50 mol% acceptor‐monomer (MSA, NEMI) units. The equilibrium constants for the formation of charge‐transfer complexes between the donor(ANE) and the acceptors(MSA or NEMI) were determined with the 1H‐NMR method KI(ANE/MSA)=0.12 and 0.09, respectively. KII(ANE/NEMI)=0.07 and 0.04 in THF and CHCl3). According to the model of the simultaneous participation of free monomers and complexes, the equations for the overall polymerization rate of co‐ and terpolymerization, with participation of one homopolymerizable monomer, were derived at the first time. The participation of free monomers and complexes to the polymerization process were determined via kinetic measurements. At low monomer concentrations, free monomers dominate, and at high monomer concentrations, the more active complexes determine the overall polymerization rate. The maximum polymerization rate was not always at the 1∶1‐monomer composition and changes with the monomer concentration. The solvent effect on the polymer compositions and on the polymerization kinetics was discussed.