Polymerization of modified diacetylenes in Langmuir films

The polymerization of a series of diacetylene Langmuir monolayers modified in the hydrophobic as well as in the hydrophilic part of the molecule was studied by measuring the kinetic changes of the mean molecular area and UV-vis spectra. The polymerization properties of the monolayers were dependent on the position of the diacetylenic unit and whether an ester or sulfonyl group was introduced in the hydrocarbon chain. The substances containing a sulfonyl group showed the highest polymerization activity. The blue-to-red transition usually observed for diacetylenes in Langmuir and Langmuir-Blodgett films due to UV irradiation was not observed, instead the studied substances formed directly a red form polydiacetylene. A first-order consecutive reaction kinetic model with a steady-state approximation was successfully adapted to the experimental results of three of the studied compounds.