Amphiphilic diacetylenes of the type HC drop C-(CH2)(n)-C drop C-C drop C-(CH2)(8)-COOH (n = 6 and 12) were synthesized. The solid-state polymerization of the bulk crystals, monolayers on the gas-water interface, and multilayers were investigated. The diacetylene moieties underwent polymerization upon irradiation by UV or gamma-rays, showing different polymerizability depending on the material form. The polymerization of the terminal acetylene groups was not observed. Enhanced polymerizability and stability of the monolayers on subphases containing LiOH are explained by a proposed model of the monolayers.