No abstract

P(NIPAM-co-FPA) contains an aldehyde group and a phenolic ester moiety is synthesized. The aldehyde group can form reversible covalent bonds with hydrazide to endow the polymer gels with self-healing properties. The self-healable polymer gel can be degraded in Na2CO3 solution based on cleavage of phenolic ester bond.

Photoredox catalyzed atom transfer radical polymerization (photo-ATRP) has emerged as a fundamental and powerful polymerization method. Herein we report a class of facilely synthesized N-aryl phenoxazines that serves as highly efficient visible-light-driven photoredox organocatalysts. The strategy of thermally activated delayed fluorescence (TADF) was introduced with the organocatalysts by constructing an orthogonally linked D–A molecular configuration. The offset between the lowest singlet S1 and lowest triplet T1 excited states (ΔE ST) is less than 0.30 eV in TADF molecules. The small ΔE ST (<0.1 eV) and the long-lived excited states (>0.1 μs) of the organocatalysts were confirmed by theoretical and experimental studies. The combination of a strong electron donor and weak electron acceptors endows the molecules with high-lying HOMOs and LUMOs, which provide a sufficiently negative excited state reduction potential E 0(PC•+/PC*) of ca. −1.5 V. The catalysts were applied in the photo-ATRP of methyl methacrylate using ethyl α-bromophenylacetate as the initiator under white-light irradiation. The photo-ATRP was successfully conducted with catalyst loadings as low as 30 ppm. The monomer scope was expanded to benzyl methacrylate (BnMA) and acrylate butyl methacrylate (BMA). Finally, the block polymer P­(MMA-b-BnMA) was synthesized, demonstrating the high chain-end fidelity of the polymers.

The statistical method was used to give the number of bonds formed for the star-branched polymer chains made by the AB + A f polymerization. On the basis of the kinetic model described by the Smoluchowski-like coagulation equation, the mean-square radii of gyration were given analytically. Furthermore, the z-and weight-average mean-square radii of gyration were investigated explicitly. The results were much different from that of the hyperbranched polymers made by the AB f type monomers, where the former had the finite values when the reaction was quantitatively completed, and the latter reached the infinite values. In principle, by varying the number of the A f type multifunctional core moieties, the average sizes, as well as the average degrees, can be controlled effectively.