The amide bond is one of the most pivotal functional groups in chemistry and biology. It is also the key component of proteins and widely present in synthetic materials. The majority of studies have focused on the formation of the amide group, but its postmodification has scarcely been investigated. Herein, we successfully develop the Michael additions of amide to acrylate, acrylamide, or propiolate in the presence of phosphazene base at room temperature. This amide Michael addition is much more efficient when the secondary amide instead of the primary amide is used under the same conditions. This reaction was applied to postfunctionalize poly(methyl acrylate-co-acrylamide), P(MA-co-Am), and it is shown that the amide groups of P(MA-co-Am) could be completely modified by N,N-dimethylacrylamide (DMA). Interestingly, the resulting copolymer exhibited tailorable fluorescence with emission wavelength ranging from 380 to 613 nm, which is a desired property for luminescent materials. Moreover, the emissions of the copolymer increased with increasing concentration in solution for all excitation wavelengths from 320 to 580 nm. Therefore, this work not only develops an efficient t-BuP4-catalyzed amide Michael addition but also offers a facile method for tunable multicolor photoluminescent polymers, which is expected to find a wide range of applications in many fields, such as in anticounterfeiting technology.
The placement of selenium (Se) atoms into polymers to achieve functional materials for diverse applications in adaptive and biomedical materials has attracted broad interest. However, the difficulty in creating well-defined Se-rich polymers is a critical limitation. In this work, we report the successful alternating and regioselective copolymerization of nonstrained γ-selenobutyrolactone with epoxides. Poly(selenide-alt-ester)s containing selenide and ester groups in each repeating unit are achieved under mild reaction conditions. The process mediated by the phosphazene base (P2)/alcohol at 25 °C exhibits high activity and living behavior, as evidenced by narrow molecular weight distributions (1.05–1.29) and switch on–off chain extension experiments. The nucleophilic attack of epoxides by selenol anions is the rate-determining step according to kinetic studies. The resultant Se-containing polyesters possess >99% alternating degree, >99% regioregularity, and programmable hydroxyl terminals. More importantly, these poly(selenide-alt-ester)s exhibit the initial thermal decomposition temperatures of up to 275 °C, low glass-transition temperatures of down to −59 °C, excellent solvability in common organic solvents, high refractive indexes (1.61–1.62), and good ionic conductivity (when doped with Li salt, 1.09 × 10–6 S/cm at 30 °C, 1.73 × 10–4 S/cm at 100 °C), indicating potential broad application prospects of these Se-rich polyesters.
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