Formation of reactive isocyanate group-containing polymers via Lossen rearrangement

We report an efficient and phosgene-free method for the synthesis of isocyanate group (NCO)-containing polymers via Lossen rearrangement. The key monomer of N-acetoxymethacrylamide (AMAA), possessing N-acetoxy amide (AA) group was synthesized from the reaction of N-hydroxymethacrylamide (MHA) with acetic anhydride. By adjusting the feed ratio of methyl methacrylate (MMA) and AMAA, a series of AA-containing polymers (P1-P3) were prepared by free-radical polymerization. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) revealed that the AA groups in polymers P1-P3 can be readily converted to isocyanate groups by heating at 130 degrees C to afford the NCO-containing polymers P4-P6 with conversion percent of 60, 77 and 78, respectively. Furthermore, the AA-containing polymers can be used as a latent NCO-containing polymer for further chemical modification, such as in-situ grafting reaction with hydroxyl compounds. The spectroscopic analyses confirmed that the dye functional group of disperse red 1 (DR1) was successfully grafted on either NCO- or AA-containing polymers.