FORMATION OF POLY(DIACETYLENE) THIN-FILMS WITH UNIFORM FLUORESCENCE

This paper presents a novel way to produce poly(diacetylene) thin film s of uniform fluorescence on a solid support. The method involves film formation at the air-water interface from a modified diacetylene mono mer using innovative spreading, crystallization, and transfer techniqu es. Pressure-area isotherms for the monomer (2,3-dihydroxypropane)pent acosa-10,12-diynoicamide reveal the optimum lateral pressure (10 mN/m) and temperature (40 degrees C) for film production. To prepare films, we apply a 2 mM solution of the monomer in chloroform to the air-wate r interface, either dropwise or as a nebulized spray. Irradiation with UV light polymerizes the film to its red, fluorescent form. Pressuriz ed nitrogen directed at the subphase surface creates turbulence in the interfacial layer, causing break-up and randomization of crystal doma ins. After stopping the surface disruption, we transfer the film to si lanized glass slides held at 40 degrees C. Heating the transfer slides eliminates holes in the film attributed to condensation of water vapo r onto the slides during transfer. The resulting film consists of unif ormly distributed crystals of less than or equal to 10 mu m, and it is free of the large cracks and defects commonly observed in solid-suppo rted poly(diacetylene) films. The transferred film has very uniform fl uorescence with a coefficient of variance of only 5% in fluorescence i ntensity based on measurements 1 mm in diameter covering the entire sl ide (2.5 cm x 7.5 cm).