The present invention is directed to a process for the cleavage of one or more starting polymers having thiocarbonylthio groups of the formula (I) into derived polymers in which the —S—(C═S)— group is transformed. The process includes contacting the starting polymer containing groups Yb with one or more reagents containing groups Xa to produce the derived polymer and a byproduct containing the groups Yb, wherein the groups Xa is one or more reactive groups and the groups Yb is an extracting group and a byproduct, which is then separated from the derived polymer by conventional separation processes. The derived polymer is free from odor or color that is sometimes associated with the starting polymer and it can be used in making optical lenses, such as high refractive index spectacle lenses.