Self‐healing polyacrylate coatings with dynamic H‐bonds between urea groups

Adding self‐healing properties to coatings is a promising way to increase their lifetime. Despite an increasing popularity, lots of self‐healing polymers are not suited for commercial coatings because they exhibit poor mechanical properties or require expensive products or high healing temperature (> 100°C). One way to obtain self‐healing abilities with good mechanical properties is by using dynamic H‐bonds as they also limit the healing temperature. To do so, urea groups are used since they are well‐known for their bonding capacity and can be readily synthesized. In this study, several methacrylate monomers containing urea groups in their side‐chain were synthesized from easily accessible amines and isocyanates in a one‐step, high‐yield synthesis. They were afterwards used in a copolymer containing methyl methacrylate and butyl acrylate monomers. The self‐healing properties of the resulting coatings were evaluated with gloss recovery and optical microscopy and the presence of H‐bonds in the most promising polymer was investigated with FTIR. The mechanical properties of the coatings as a function of time were checked by nanoindentation creep test. We were able to obtain an affordable, easily prepared polymer that suits the requirements for protective coating applications and shows a complete healing after heating at 75°C for 1 h. In this work, self‐healing polyacrylate coatings were prepared using monomers containing urea groups in their side‐chains. Those monomers were obtained from easily accessible amines and isocyanates in a one‐step synthesis. Self‐healing and nanoindentation creep tests highlighted the beneficial impact of H‐bonds on the self‐healing and mechanical properties simultaneously. A coating showing a complete self‐healing after heating for 1 h at 75°C was successfully obtained.