High molecular weight mechanochromic spiropyran main chain copolymers via reproducible microwave-assisted Suzuki polycondensation

摘要: Suzuki–Miyaura polycondensation (SPC) is widely used to prepare a variety of copolymers for broad range applications. Although SPC protocols are often in many instances, the limits this method and issues molecular weight reproducibility not looked at detail. By using spiropyran-based (SP) mechanochromic copolymer, we present an optimized protocol microwave-assisted synthesis mechanochromic, alternating copolymer P(SP-alt-C10) via that allows reproduction distributions. Several parameters such as microwave power, temperature, stoichiometry, ligand screened, leading weights up Mw ∼ 174 kg mol−1. The process optimization guided by NMR end group analysis which shows dehalogenation, oxidative deborylation SP cleavage limiting factors impede further increase molar mass, while other classical side reactions protiodeborylation observed. Embossing films yields colored merocyanine (MC) P(MC-alt-C10) undergoes thermally facilitated back reaction P(SP-alt-C10). DFT suggests barrier → MC transition has two contributions, with first one being related color change second internal bond reorganizations. height 1.5 eV, ease either due residual energy stored deformed polymer matrix, or arises from isomer thermodynamically most stable state.