POSS-based starlike hybrid helical poly(phenyl isocyanide)s: their synthesis, self-assembly, and enantioselective crystallization ability

Polyhedral oligomeric silsesquioxane (POSS) based starlike hybrid helical poly(phenyl isocyanide)s (PPIs) with well-defined structures were designed and prepared in this contribution. The POSS modified with Pd(ii) complexes (POSS-Pd(ii)) was firstly obtained. Then well-defined starlike hybrid helical PPIs with POSS cores were synthesized through the polymerization of phenyl isocyanide monomers using POSS-Pd(ii) as the initiator. The polymerization proceeded in a living and controlled manner. Meanwhile, polymerization of chiral phenyl isocyanides with decyl chain modified pendant l- or d-alanine afforded optically active hybrid starlike helical PPIs with preferred handedness. What's more, amphiphilic starlike hybrid helical PPI block copolymers showing thermoresponses were easily obtained, and their self-assembly and thermo-responsive behaviours were studied. In addition, cross-linked hybrid helical PPIs were obtained via the transesterification reaction between pentafluorophenyl ester and cystamine. Benefitting from the essential chirality of the handed helical PPIs, the cross-linked hybrid PPIs showed excellent ability in the enantioselective crystallization of racemic compounds. The enantiomeric excess (ee) of the induced crystal of threonine could be up to 95%.