Conventional radical polymerization is widely used in industries due to its simple polymerization conditions. But, molecular weight of polymers are difficult to control in this method. To achieve control over molecular weight and molecular weight distribution, many controlled radical polymerization methods have been proposed such as INIFERTER, NMP, RAFT and ATRP. In the field of ATRP, due to its simplicity and versatility, more than 7000 research articles have been published in the reputed journals during the last 15 years. But polyurethane-based tri-block copolymers have not been reported so far through ATRP and hence this book concentrates on novel routes to synthesize these tri-block copolymers via ATRP. Four different types of polyurethane macroinitiators for ATRP have been synthesized and used for the polymerization of vinyl and acrylate monomers. Results show that the present macroinitiators polymerize monomers through ATRP mechanism. These macroinitiators are highly potential to polymerize wide variety of monomers and resulting block copolymers would be very useful for academic as well as industrial research.