Hydrogen-Transfer Alternating Copolymerization of P-Ethenyl-N-n-propylphosphonamidic Acid Ethyl Ester with Cyclic Phosphonites Involving Oxidation-Reduction Process

The present paper describes the alternating copolymerization of P-ethenyl-N-n-propylphosphonamidic acid ethyl ester (1) with cyclic phosphonites (2). The copolymerization took place without added catalyst to produce 1:1 alternating copolymer 3. During the copolymerization the oxidation-reduction reaction of monomers occurred. Monomer 1 behaved as an oxidant monomer (Mox) whereas 2 acted as a reductant monomer (Mred). The structure and composition of copolymers were determined by 1H and 31P NMR spectra as well as the hydrolysis experiments. The copolymerization is reasonably explained by a mechanism of propagation via zwitterion intermediates. The apparent monomer reactivity ratios determined in benzonitrile at 130°C were r1=0.00 and r2(six-membered)=0.34.