In this sense, trimethylolpropane [2-ethyl-2-(hydroxymethyl)-1, 3-propanediol] trimethacrylate is an example of a trifunctional molecule because it has three methacrylate functional groups attached, and tetramethylolpropane tetramethacrylate is an example of a tetrafunctional molecule because it has four methacrylate functional group attached.