Synthesis of poly(ethylene adipate) with a stable nitroxyl radical at bothchain ends, and applications to a counter radical for living radical polymerization

Synthesis of poly(ethylene adipate) (PEA) with 2,2,6,6-tetramethylpiperidin e-1-oxyl (TEMPO) at both chain ends was attained by reaction of 4-hydroxy-T EMPO and PEA with isocyanate groups at the terminals. PEA obtained was foun d to have the living nitroxyl radical, because the electron spin resonance (ESR) spectrum of the polymer manifested a typical three sharp signals base d on TEMPO. TEMPO-supported PEA served as a polymeric counter radical for t he radical polymerization of styrene, to quantitatively give the block copo lymer of ethylene adipate and styrene. Polymerization proceeded in accordan ce with a living mechanism, because the molecular weight of the copolymer w as proportional to conversion of styrene and reciprocal of initial concentr ation of TEMPO attached to PEA. Analysis of the copolymer using a thin laye r chromatography/flame ionization detection (TLC/FID) clarified that the co polymer contained no homopolystyrene. This absence of homopolystyrene impli es that no diblock copolymer is formed during polymerization. H-1 NMR analy sis demonstrated the structure of copolymer obtained to be A-B-A triblock.