Study On New Catalytic System For Reactive Radical Polymerization

Atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) polymerization are two widely used reversible deactivation radical polymerization (RDRP) techniques as they can be applicable to a wide range of monomers and produce well-defined polymer with predictable molecular weight and low polydipersity index (PDI). However, there exist some problems, which limit their application, such as, the reaction rate of ATRP system is usually slow and the system usually needs a large amount of metal catalyst. For RAFT method, the RAFT reagent is extremely unstable and usually need to prior to use, thus limiting its industrial applications. Based on the features of ATRP and RAFT mediating systems, we developed a novel and stable mediating agent (iron dithiobenzoic, Fe(S(S=C)Ph)3) which can reduce the amount metal catalyst used in ATRP system and keep the controllability over the polymerization, Moreover the new compound possesses other merits, such as easy preparation, low cost, high stability, and etc.Novel mediating agent (Fe(S(S=C)Ph)3) was successfully synthesized for concurrent atom transfer radical polymerization (ATRP) and reversible addition fragmentation transfer (RAFT) of methyl methacrylate (MMA), using azobis(isobutyronitrile) (AIBN) as thermal radical initiator and triphenylphosphine (PPh3) as the ligand. The effect of the amount of metal catalyst and the molar ratio of AIBN/Fe(S-(S=C)-Z)3 or MMA/2AIBN on the polymerization reaction were also investigated indetail. The experiments results showed that compared with FeBr3 and FeCl3, Fe(S-(S=C)-Z)3 show excellent polymerization. When the ratio of AIBN to Fe(S-(S=C)-Ph)2 is as high as 2:1 or 4:1, polymer with low Mw/Mn was obtained. As two mediating agents, ATRP activator (Fe(S-(S=C)-Z)2) and RAFT agent (R-S-(S=C)-Z), which may be formed in situ, the current occurred ATRP and RAFT procedure can reduce the amount of mediating agents needed in this system. The resultant PMMAs have narrow Mw/Mn (<1.35) values when the ratio of [MMA]o/2[AIBN]o is 1600:1. Living polymerization characteristics were confirmed by kinetic studies, GPC and 1H NMR and GPC analyses, as well as chain-extension reaction.