- Polydiacetylenes (PDAs) comprise a class of chromatic polymers which have attracted significant interest over the past 40 years as a promising platform for chemo- and bio-sensing. Specifically, the unique colorimetric and fluorescent transformations of PDA, induced by varied external stimuli, are a core property of these polymers, and have been widely exploited for diverse applications. In this review, we focus on recent developments in PDA chemistry, materials, and practical applications. We summarize the progress in development of new synthetic routes and assembly methods resulting in enhanced chromatic properties and interesting molecular configurations. We further outline the challenges that still exist for practical utilization of PDA technology, and possible future directions.