Synthesis of block copolymers via atom transfer radical polymerization and 'click chemistry' grafted from pre-functionalized polypropylene surfaces using gamma irradiation

In this article, we demonstrate a new approach to grafting block copolymers from polypropylene substrates, using gamma irradiation, in the presence of transfer agent (CBr4) and terminator agents (CuBr2 and I-2) and monomer. Varying the concentration of CBr4 and CuBr2 exerts control over both the molecular weight of grafted polymers and the surface density of tethered bromine groups. The bromine end-groups were subsequently exploited to reinitiate polymerization from the surface via atom transfer radical polymerization (ATRP), yielding block copolymers and terpolymers. ATR-FTIR, XPS and EDX/SEM were used to confirm the successful synthesis of surface-tethered block copolymers. In a similar approach using I-2 as terminator agent, we functionalized PP surfaces with iodine end-functional graft polymers. The presence of iodine was then exploited to grow poly(methyl acrylate) from the surfaces using iodine transfer polymerization. The halogenated (Br), gamma grafted surfaces were then subjected to organic functionalization reactions via two different approaches: (i) azide-alkyne click chemistry and (ii) thio-bromo nucleophilic substitution. The successful click functionalization of grafted-PP was verified using both ATR-FTIR and XPS analyses.