Synthesis and properties of chiral self-assembling lamellar polydiacetylene systems with very-long-range order

Two new, very accessible, chiral, self-assembling phospholipid analogues containing diacetylenic units in the middle of their acyl chains were prepared by very simple and highly efficient routes. Films were cast and then polymerized by activation with UV light or doped with iodine. X-ray diffraction, NMR spectroscopy measurements, and molecular mechanics analyses using the MM3 force field indicated that the acyl chains are closely packed in a parallel fashion. The new molecules and the polymerized films derived from them were characterized by a variety of physical methods including confocal polarized light microscopy, atomic force microscopy, and near-infrared spectroscopy. These analytical methods showed that the unpolymerized molecules are able to form lamellar systems with very-long range order. They formed very uniform, extremely flat, thin films which are readily polymerized to give extensively conjugated systems which absorbed well out into the near-infrared region unlike typical polydiacetylenes. The propensity of the new molecules to form such well-packed structures arises from their resemblance to diacyl glycerolipids, with the pi-stacking interaction from the diacetylene units giving extra stabilization. The results indicate that this is an excellent approach for preparing ordered polydiacetylene systems for use in designing advanced materials.