Autocatalytic Self-Sorting in Biomimetic Polymer

Abstract

Autocatalytic self-sorting in the biomimetic poly­(cystamine methacrylamide hydrochloride) (PCysMA) is presented, whose units comprise lysine-mimetic alkyl­ammonium ions and cystine-mimetic alkyl disulfide spacers. The block copolymer with poly­(2-hydroxy­propyl­methacrylamide) was synthesized directly by RAFT in acidic water under visible light irradiation at 25 °C. Disulfide exchange can be initiated by the terminal thiolates as generated by alkalization-induced aminolysis. 65–67% CysMA units sort into hydrophobic polymer disulfides and water-soluble cystamine at pH 10.5. Moreover, intermediate reactions occur in the presence of copper ions, i.e., Cu­(II)–NH₂ coordination, aminolysis, NH₂-to-SH substitution, and cupric-to-cuprous reduction in metal centers, thus autocatalytic self-sorting with essentially 100% conversion at pH 8.8. UV–vis spectroscopy, ¹H NMR, atomic absorption spectroscopy, and elemental analysis confirmed this ideal self-sorting. Dynamic light scattering and atomic force microscopy identified supramolecular-to-supracolloidal self-assembly with concomitant release of cystamine molecules and intermediate cuprous complexes. Such a self-sorting underlines an amazing prospect for the use of a single polymer to achieve artificial reaction complexity, hierarchy, and metabolic process, with minimal synthetic efforts