Macromolecular design based on living radical polymerization using a stable nitroxyl radical

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), a stable nitroxyl radical, se rves as a counter radical for living radical polymerization of styrene, giv ing a polymer with a narrow polydispersity. in the TEMPO-mediated polymeriz ation, the concentration of a growing polymer chain was identical to the in itial concentration of TEMPO, and therefore, TEMPO was attached to a chain end of all polystyrenes. Polymerization of styrene by 4-hydroxy-TEMPO quant itatively gave hydroxy-terminated polystyrene, indicating that the TEMPO-me diated polymerization can be expanded to a method of end-functionalization. TEMPO-supported polymers, obtained from anionic polymerization, cationic p olymerization, or polycondensation, acted as polymeric counter radicals for the radical polymerization of styrene, giving block copolymers quantitativ ely. This method involves transformation from these polymerizations to livi ng radical polymerization, using TEMPO as a transforming agent. The TEMPO-s upported polymers accelerated the polymerization to produce the block copol ymers with high molecular weights in a short time. The conversion of styren e reached 90% only after 24 h in the polymerization using the TEMPO-support ed poly (epsilon-caprolactone), while it took 4 days to reach over 80% in t he polymerization of styrene by 4-methoxy-TEMPO, A heteroarm star block cop olymer and a hairpin type of polymer were also prepared by the polymerizati on using TEMPO-attached cyclic triphosphazene and a biradiral compound of T EMPO, respectively. The TEMPO-mediated polymerization was able to create ma cromolecular architectures through designing initiators, based on the fact that initiators and TEMPO exist separately. Polymerization of styrene by a macroazoinitiator of poly(dimethylsiloxane) and TEMPO produced AB type bloc k copolymers. Novel random block copolymers consisting of two types of rand om copolymers of alkoxystyrenes and styrene were also prepared.