Two Structurally Different Polymers from a Single Monomer.

We designed and synthesized a malonamide-derived monomer, containing azide and alkyne units, for topochemical polymerization to yield nylon (n,3). This monomer on crystallization gave two concomitant polymorphs and . Both the polymorphs show crystal packings that are suitable for topochemical azide-alkyne cycloaddition polymerization. On heating, polymorph reacts regiospecifically to give 1,4-disubstituted-1,2,3-triazolyl-linked polymer, whereas polymorph yields 1,5-disubstituted-1,2,3-triazolyl-linked polymer regiospecifically. In the case of polymorph , polymerization proceeds perpendicular to the hydrogen bonding direction, whereas in , the reaction occurs along the hydrogen bonding direction. This results in the two structurally different polymers having distinct topologies. These single-crystal-to-single-crystal polymerizations allowed us to study their structure at atomic resolution by single-crystal X-ray diffraction. This is the first report on the topochemical synthesis of two structurally isomeric polymers from a single monomer.