A Synthetic Route to Sulfobetaine Methacrylates with Varying Charge Distance

A general synthetic strategy is described that enables access to a library of new sulfobetaine methacrylates starting from commercially available precursors. The three-step procedure allows the distance between the quaternary amine and the sulfonate group (inner charge distance) to be varied by selecting the corresponding dibromoalkane in the first step. A key step is the final esterification, in which methacrylic acid acts as solvent as well as reagent for the zwitterionic hydroxy intermediates. Thus, it is possible to synthesize monomeric precursors with up to twelve methylene groups between the positive and the negative charge. A selection of these monomers has been successfully tested for their ability to polymerize using free-radical polymerization.