Photopolymerization Properties Research Articles

Effects of side-group interactions on pressure-induced chromism of polydiacetylene monolayer at a gas-water interface

The photopolymerization properties of polydiacetylene (PDA) and the surface pressure dependence of its excitonic absorption were investigated using in situ reflection spectroscopy of the monolayer at a nitrogen-gas-water (pure water, CdCl 2 aqueous solution) interface. In a poly-(heptacosa-10,12-diynoic acid) containing n-alkyl chain side-groups, reversible chromism induced by surface pressure change was found for the first time in a partially polymerized PDA monolayer on pure water; blue and red forms of PDA were predominant at low and high surface pressure respectively. However, in a partially polymerized dibutyl-4,19-dioxo-5,18-diaxa-3,20-diaza-10,12-docosadiyne dioate containing urethane side-groups, irreversible chromism from blue to red was only induced by increasing surface pressure. These results suggest that the different chromism behaviour of the two diacetylenes reflects the different side-group interactions: a van der Waals' interaction and a hydrogen-bonding interaction.