Insight into diacetylene photopolymerization in Langmuir‐Blodgett films using simultaneous AFM and fluorescence microscopy imaging

A phase‐separated monolayer film comprised of a mixture of 10, 12‐pentacosadiynoic acid (PCDA) with perfluorotetradecanoic acid (PF; CF₃(CF₂)₁₂COOH) has been characterized using a microscope that is capable of simultaneous atomic force microscope (AFM) imaging and fluorescence imaging. Design criteria for this instrument are described, as well as its application to investigating the mixed film systems. The product of PCDA photopolymerization has two phases, a red phase with strong fluorescence and a blue phase with no fluorescence. With the help of the dual AFM‐fluorescence microscope, it was found that both the red and the blue phase polymers were produced in the same sample from photoillumination, and the relative quantities of the different phases were quantified. Further, the importance of intrinsic mechanical stress in the films is discussed in terms of its influence on selectivity towards the red polymer phase.