Controlled radical initiators, reaction mixtures containing the controlled radical initiators and various ethylenically unsaturated monomers, polymeric materials formed from the reaction mixtures, crosslinkable compositions containing the polymeric materials, crosslinked compositions formed from the crosslinkable compositions, and articles containing the polymeric materials, the crosslinkable compositions, or the crosslinked compositions are provided. The controlled radical initiators are bis-dithiocarbamate or bis-dithiocarbonate compounds having a single carbon between the two dithiocarbamate or dithiocarbonate groups. Also attached to that single carbon is a ketone group.