Stereoregular Brush Polymers and Graft Copolymers by Chiral Zirconocene-Mediated Coordination Polymerization of P3HT Macromers

Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH(2)-MA and P3HT-(CH(2))(2)-MA, have been synthesized, and P3HT-(CH(2))(2)-MA has been successfully homopolymerized and copolymerized with methyl methacrylate (MMA) into stereoregular brush polymers and graft copolymers, respectively, using chiral ansa-zirconocene catalysts. Macromer P3HT-CH(2)-MA is too sterically hindered to polymerize by the current Zr catalysts, but macromer P3HT-(CH(2))(2)-MA is readily polymerizable via either homopolymerization or copolymerization with MMA in a stereospecific fashion with both C(2)-ligated zirconocenium catalyst 1 and C(s)-ligated zirconocenium catalyst 2. Thus, highly isotactic (with mm% ≥ 92%) and syndiotactic (with rr% ≥ 93%) brush polymers, it-PMA-g-P3HT and st-PMA-g-P3HT, as well as well-defined stereoregular graft copolymers with different grafted P3HT densities, it-P(M)MA-g-P3HT and st-P(M)MA-g-P3HT, have been synthesized using this controlled coordination-addition polymerization system under ambient conditions. These stereoregular brush polymers and graft copolymers exhibit both thermal (glass and melting) transitions with T(g) and T(m) values corresponding to transitions within the stereoregular P(M)MA and crystalline P3HT domains. Acceptor molecules such as C(60) can be effectively encapsulated inside the helical cavity of st-P(M)MA-g-P3HT to form a unique supramolecular helical crystalline complex, thus offering a novel strategy to control the donor/acceptor solar cell domain morphology.