The present invention is directed to a novel polymerizable organic composition comprising one or more radically polymerizable monomers with at least one radically polymerizable monomer having at least two (meth)acryloyl groups that have backbone linkages selected from thiourethane linkages, dithiourethane linkages, combinations of thiourethane linkages and dithiourethane linkages. The present invention is also directed to polymerizates prepared from the polymerizable organic composition, shaped articles prepared from the polymerizable compositions, and photochromic articles that may be prepared from the polymerizable organic composition of the present invention.