The CuBr/2,2 -bipyridine (bpy)-catalyzed atom transfer radical polymerization (ATRP) of styrene (St) initiated by well-defined poly(styrene-alt-N-[4-(α-bromopropyloxy)phenyl]maleimide) [P(St-alt-BPPM)] in cyclohexanone at 60 and 80 ℃ was investigated. The results showed that the reaction appeared to follow pseudo-first order kinetics, and the molecular weight (M_W) of the polymer P(St-alt-BPPM)-g-PS increased with the monomer conversion. A lower reaction temperature would reduce the reaction rate and lead to a narrower molecular weight distribution of the P(St-alt-BPPM)-g-PS. The M_W data of the PS side chains confirmed that the process was in a controlled fashion. The ATRP of St cannot be successfully initiated by low-M_W analogue under similar conditions, so using multi-functional macroinitiator would significantly reduce the reaction temperature. Such an acceleration effect was attributed to the diffusion of CuBr/bpy from the macro-initiator coil outside to inside and that of CuBr₂/bpy from inside to outside, resulting in an enhanced concentration of propagating radicals inside the coil and an faster polymerization rate.

Key words: styrene, atom transfer radical polymerization (ATRP), multi-functional macroinitiator, diffusion effect, acceleration