An amphiphilic diacetylene with thymine (DA-Thy) was newly synthesized. The
amphiphile can form solid-state monolayer and photopolymerize with UV ligh
t irradiation at the air-water interface to form blue and red forms of poly
diacetylene. Shapes of the crystalline domain of the polydiacetylene monola
yer were changed by base pair formation between DA-Thy and adenine nucleoba
se dissolved in the water subphase.