Synthesis of A₂B and A₂B₂ type miktoarm star co-polymers by combination of ATRP or ROP with photoinduced radical polymerization

Well-defined polystyrene (PSt) or poly(ε-caprolacone (PCL) precursor polymers, possessing central or end 2,5-dibromo-1,4-phenylene, 2,5-dibromo-benzene or 3,5-dibromobenzene moieties, were synthesized by controlled polymerization methods, such as Atom Transfer Radical Polymerization (ATRP) or Ring Openining Polymerization (ROP). Further modification of these polymers in one or two reaction steps at the aromatic bromine atoms afforded bi-functionalized prepolymers. The first reaction step was a Suzuki coupling reaction between aromatic bromine functional polymers and 3-aminophenylboronic acid, yielding di-amino-containing intermediates. The second step was a condensation reaction between the di-amino functional intermediates and 4-(dimethylamino)-benzaldehyde. Thus, dimethyl-amino functional prepolymers were synthesized as well. The presence of amino or N,N′-dimethyl amino functional groups in the structure of intermediate polymers permitted co-polymerization with methyl methacrylate (MMA) by photoinduced radical polymerization by using benzophenone or Erythrosin B as photosensitizer and 4- or 3-armed star co-polymers (PSt-PMMA or PCL-PMMA) were obtained. The structures of all the starting polymers, intermediate polymers and final co-polymers were analyzed by spectral methods (¹H-NMR, IR), as well as by GPC measurements. DSC analyses were performed for prepolymers and co-polymers and compared.