24 | December 2021 www.facs.website Figure 3 (left): Seal-healable and mechanically robust polymers. (a) Chemical structure and demonstration of the quick self-healing of poly(ether thiourea) at ambient temperatures.27a (b) Nonlinear H-bonding arrays ensure the mechanical robustness of the polymer. (c) Chemical structure of the humidity resistant, self-healable, and mechanically robust poly(ether thioureaco-dicyclohexylmethane thiourea).27b (d) Image of the material shown in (c). Figure 4 (below): (a) Schematic representation of solvent-free autocatalytic supramolecular polymerization (SF-ASP).19 (b) Chemical structures of the phthalonitrile precursor, PNC4, and the phthalocyanine monomer, PCC4, formed at the cross-sectional ends of the polymer chain. (c) Optical images of PNC4, sandwiched between glass plates at 160°C, at different reaction times – adapted from Nature Materials. in an exceptionally high yield of 83% by simply washing the reaction mixture with methanol. This value far exceeds the 20 to 25% yield reported for the typical solution-phase synthesis of phthalocyanine derivatives. As illustrated in Fig. 4a, the crystalline fibers preorganize the monomer precursor PNC4 on
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