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

Abstract

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.