An aminochalcone-diacetylene compound of Formula 1A:

##STR00001##

wherein R.sup.1 and R.sup.2 are independently selected from H and C.sub.1-C.sub.3 alkyl, A denotes a linkage connecting the chalcone and diacetylene units, m and n are independently integers in the range of 2 to 18, and the corresponding protonated form/ammonium salt of Formula 1B:

##STR00002##

wherein X is a counter anion. The disclosure further discloses the corresponding chromatic polydiacetylenes and polydiacetylenes-based sensors for detecting ammonia.