Simultaneous and in situ syntheses of an enantiomeric pair of homochiral polymers as their perfect stereocomplex in a crystal

Circumventing the issues of conventional stereocomplexation of preformed polymers, herein, we synthesize two enantiopure polymers of opposite chirality simultaneously and in situ as their 1:1 stereocomplex via topochemical polymerization. We design and synthesize an inositol-based achiral monomer for topochemical ene-azide cycloaddition (TEAC) polymerization. In the crystal, the monomer exhibits conformational enantiomerism, and its conformational enantiomers are self-sorted in an arrangement for TEAC polymerization to yield two enantiopure polymers of opposite chirality. Upon heating the monomer crystals, each self-sorted set of conformational enantiomers undergoes regio- and stereospecific polymerization in a single-crystal-to-single-crystal fashion, generating two 1, 4-triazolinyl-linked polymers of opposite chirality simultaneously. The new chiral carbons in all the triazoline rings of a particular polymer chain have the same absolute configuration. These homochiral polymer strands align parallelly, forming a layer, and such enantiopure layers of opposite chirality stack alternately, forming a perfect 1:1 stereocomplex, which we confirmed using single-crystal XRD analysis. Stereocomplexation is a powerful strategy for improving polymer properties but inefficient complexation remains a major challenge in stereocomplex formation. Here, the authors circumvent the difficulties of conventional stereocomplexation of preformed polymers and, synthesize two enantiopure polymers of opposite chirality simultaneously and in situ as their stereocomplex via topochemical polymerization.