Synthesis of core cross-linked star polymers carrying helical poly(phenyl isocyanide) arms via “core-first” strategy and their surface chiral recognition ability

Abstract

A norbornene functionalized alkyne-Pd(II) complex was designed and synthesized, which copolymerized with a bisnorbornene cross linker via ring-opening metathesis polymerization (ROMP) afforded a cross-linked Pd(II) macroinitiator. Living polymerization of phenyl isocyanides with the Pd(II) macroinitiator lead to the formation of well-defined core cross-linked star polymer carrying helical poly(phenyl isocyanide)s arms. Because of the living nature of Pd(II)-initiated phenyl isocyanide polymerization, a series of star polymers with controlled structure and tunable compositions was readily prepared. Optically active star polymers with excess of one handed helical arms were obtained by using enantiopure phenyl isocyanide monomers. Such star polymer exhibited excellent chiral recognition ability. The contact angle of the star polymer is strongly dependent on the chirality of the D/L-phenylglycinol droplets. The enantioselective surface recognition can be further applied to the chiral resolution of racemic D/L-phenylglycinol. The enantiomeric excess (ee) of the isolated enantiomer is up to 75%. The chiral star polymers can also be used to induce enantioselectively crystallization of racemic Boc-alanine. The ee value of the induced enantiomer can be up to 91%.