Synthesis of Unimolecular Micelles with Incorporated Hyperbranched Boltorn H30 Polyester modified with Hyperbranched Helical Poly(phenyl isocyanide) Chains and their Enantioselective Crystallization Performance

Abstract

Here, the fabrication of unimolecular micelles functionalized with helical polymeric chains as a chiral nucleating agent in enantioselective crystallization is reported. Starting from a fractionated hyperbranched polyester (Boltorn H30), the ring-opening polymerization of l-lactic acid (LLA) and subsequent terminal-group modification affords the alkyne-Pd(II)-anchored hyperbranched macroinitiator (H30-PLLA-Pd). By taking advantage of a Pd(II)-catalyzed living polymerization of chiral pendant modified l- or d-phenyl isocyanide (PI) monomers, well-defined chiral unimolecular micelles (H30-PLLA-PPI) grafted with radiating helical PPI coronas of one predominant screw sense are obtained. The resultant chiral materials demonstrate excellent application in the enantioselective crystallization of racemic threonine in water, and a 92% enantiomeric excess value of the residual solution is obtained. It is believed this present proof of concept and methodology are facile and powerful for preparing novel and versatile chiral materials with different topological structures, not only applicable to PPI but also to other types of polymers.