Progress in polydiacetylene nanowires by self-assembly and selfpolymerization

In recent years, there has been immense interest in studying nanoscale aggregate structures derived from various polydiacetylenes (PDAs). The motivation for this is not only to understand the fundamental aggregate structures at different scales, but also to explore their potential for future technological applications. PDAs have been made sensitive to external stimuli such as light and chemical entities by incorporating a spectroscopically active moiety or a receptor unit as the head group of the PDA molecule. This makes them suitable for applications such as sensing and actuating. Furthermore, owing to the delocalization of pi-conjugated electrons, PDAs have been exploited as good candidates for organic nonlinear optical materials. This Focus Review highlights some of the instructive work done by various groups to develop well-defined one-dimensional assembly systems with a highly structural aspect ratio, which can be directly imaged by microscopic techniques.