Topochemical synthesis of different polymorphs of polymers as a paradigm for tuning properties of polymers

Raja Mohanrao,Kana M Sureshan,Kuntrapakam Hema

doi:10.1038/s41467-020-14733-y

Abstract

Different packing is a mechanism through which nature can produce materials of different properties from the same basic units. There is great interest in constructing different forms of the same polymer by utilising different packing. Common solution-synthesized polymers are amorphous and their post-synthesis crystallization into different topologies is almost impossible. Here we show solid-state polymerization of different reactive polymorphs of a monomer pre-organized in different topologies. Trimorphs of a dipeptide monomer pack in a head-to-tail fashion, placing the azide and alkyne of adjacent monomers in proximity. On heating, these crystals undergo a topochemical azide-alkyne cycloaddition reaction yielding triazole-linked polymer in three different crystalline states; one with antiparallel arrangement of polymer chains, another with parallelly oriented chains, and a third form containing a 1:1 blend of two different conformers aligned in parallel. This approach of exploiting different polymorphs of a monomer for topochemical polymerization to yield polymorphs of polymers is promising for future research.

Highlights

Different packing is a mechanism through which nature can produce materials of different properties from the same basic units
Polymorphism, the ability of a solid compound to exist in different crystalline forms, originates from different packing of molecules and there is an ongoing quest for polymorphic forms of crystalline materials in pursuit of attractive properties[32,33]
Polymerization under mild conditions, we anticipated that these two polymorphs would undergo topochemical azide-alkyne cycloaddition (TAAC) polymerization. Employing these polymorphs for the topochemical reaction would be interesting since the difference in the packing of monomer molecules could be exploited for the synthesis of structurally and functionally different forms of the same polymer

Summary

Introduction

Different packing is a mechanism through which nature can produce materials of different properties from the same basic units. A plausible way to have access to different forms of polymers having different properties is the topochemical polymerization of different reactive polymorph(s) of a particular monomer[34]. We report topochemical polymerization of three different polymorphs of a monomer to yield three different forms (polymorphs) of the polymer having very different packing and properties.

Results

Conclusion