Unexpected thermally stable, cholesteric liquid-crystalline helical polyisocyanides with memory of macromolecular helicity.

The achiral sodium salt of poly(4-carboxyphenyl isocyanide) (poly-1-Na) folds into a one-handed helix induced by optically active amines in water. The induced helicity remains when the optically active amines are completely removed, and further modification of the side groups to amide residues is possible without loss of memory of macromolecular helicity. Although the helical poly-1-Na loses its chiral memory at high temperature, helical polyisocyanides modified with achiral primary amines, which no longer have any chiral components, keep their memory perfectly even at 100 degrees C in N,N-dimethylformamide in some cases and exhibit cholesteric liquid-crystalline phases, thus providing a robust scaffold with heat resistance to which a variety of functional groups can be introduced.

An unprecedented memory of macromolecular helicity induced in an achiral polyisocyanide in water.

We have found an unprecedented memory of macromolecular helicity induced in an achiral sodium salt of poly(4-carboxyphenyl isocyanide) (poly-1-Na). Poly-1-Na folds into a one-handed helix through configurational isomerization around the C=N backbones by interactions with optically active amines in water. The helix remains when the optically active amines are completely removed, and further modifications of the side group to carboxy and esters can be possible without loss of the macromolecular helicity memory.