Living/controlled radical polymerization of dimethyl(methacryloyloxy)methyl phosphonate (MAPC1) has been attempted using degenerative transfer to produce block copolymers. RAFT polymerization of this monomer is sensitive to very low level of oxygen and in any case limited to low monomer conversion. Reverse iodine transfer polymerization (RITP) leads to higher monomer conversion with a limited amount of living polymer (55% by 1H NMR), precluding an efficient synthesis of block copolymers. A PMMA‐b‐PMAPC1 diblock copolymer was therefore synthesized by iodine transfer polymerization (ITP) of MAPC1 from a PMMA‐I macro‐chain transfer agent prepared by RITP. The diblock copolymer, purified by selective precipitation, contains an average of five MAPC1 units and has potential an adhesive and as a corrosion inhibitor.