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

Yang Wang; Travis S Bailey; Miao Hong; Eugene Y-X Chen

doi:10.3390/polym9040139

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

Polymers (Basel). 2017 Apr 13;9(4):139. doi: 10.3390/polym9040139.

Authors

Yang Wang^{1

2}, Travis S Bailey³, Miao Hong⁴, Eugene Y-X Chen⁵

Affiliations

¹ Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA. Yang.Wang@colostate.edu.
² School of Fundamental Sciences, China Medical University, Shenyang 110122, China. Yang.Wang@colostate.edu.
³ Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO 80523-1370, USA. Travis.Bailey@colostate.edu.
⁴ State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China. miaohong@sioc.ac.cn.
⁵ Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA. eugene.chen@colostate.edu.

Abstract

Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH₂-MA and P3HT-(CH₂)₂-MA, have been synthesized, and P3HT-(CH₂)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-CH₂-MA is too sterically hindered to polymerize by the current Zr catalysts, but macromer P3HT-(CH₂)₂-MA is readily polymerizable via either homopolymerization or copolymerization with MMA in a stereospecific fashion with both C₂-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 C₆₀ 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.

Keywords: brush polymer; graft polymer; poly(3-hexylthiophene); stereoregular polymer; zirconocene.