Anion Migrated Ring Opening and Rearrangement in Anionic Polymerization Induced C7 and C8 Polymerizations

Establishing novel polymerization mechanisms to regulate carbon skeleton structures is a formidable challenge in polymer chemistry. Here, we propose a strategy to synthesize unique C7 and C8 skeleton polymers through living anionic polymerization. Specifically, we investigated the polymerization behavior of two diene monomers, (1-cyclopropyl-1,3-butadien-1-yl)benzene (CPBB) and (1-cyclobutyl-1,3-butadien-1-yl)benzene (CBBB), with high ring strain substituents in detail. The characterization results showed that 4,1-addition of CPBB/CBBB nearly did not result in the cycloalkane group further undergoing the anion migrated ring-opening (AMRO) reaction in the absence of polar additives, and the obtained polymers exhibited a C4 skeleton structure (>95%). However, the AMRO reaction mainly occurred after 4,3-addition of CPBB/CBBB in the presence of polar additives, which promoted the formation of C7 and C8 skeleton polymers (>95%). Therefore, the content of C4 and C7/C8 skeleton structures in the chain can be controlled by adjusting the mode of CPBB/CBBB additions, such as the addition of additives, regulation of the reaction temperature, and adjustment of the electronegativity of substituents in the CPBB/CBBB structure. The polymerization mechanism was clearly confirmed using nuclear magnetic resonance (NMR) and density functional theory (DFT) calculations. Furthermore, the unique C7 and C8 polymerizations proposed in this study provide the high atomic economy for the reactant monomers. Additionally, thermal properties of synthetic C4, C7, and C8 polymers were also evaluated by differential scanning calorimetry (DSC) measurements. Interestingly, the CPBB polymer with a C7 skeleton structure exhibited bright yellow-green cluster luminescence (CL) and a relatively high quantum yield (QY; 19.1%). The CBBB polymer with a C8 skeleton structure displayed faint blue-green CL and a low QY (2.4%). However, the CL properties of CPBB/CBBB polymers with a C4 skeleton were not found.