Degradable multisegmented polymers synthesized by consecutive radical addition-coupling reaction of α,ω-macrobiradicals and nitroso compound

摘要

A consecutive radical addition-coupling reaction induced by spin-trapping agent is applied to produce degradable multisegmented polymer using α,ω-dibromo polymer as a precursor. The macroradical generated by single electron transfer process catalyzed by Cu/PMDETA from α,ω-dibromo polymer can be efficiently captured by 2-methyl-2-nitrosopropane (MNP), which results in nitroxide radical. The in situ formed nitroxide radical immediately undergoes cross-coupling reaction with polymeric radical, generating block polymer bridged with alkoxyamine moiety. The consecutive radical addition-coupling reaction generates multisegmented polymer via step-growth mechanism. Different multisegmented polymers have been prepared from α,ω-dibromo-PS, PtBA, and PtBA-PS-PtBA. The block number of multisegmented polymers can be tailored by varying the feed ratio of α,ω-dibromo precursor to MNP. The multisegmented polymer can be degraded in the presence of hydrogen atom donor or air, and the molecular weight distribution transformed back into shape of its original precursor as it is conjugated by alkoxyamine moieties.