The amphiphilic diolefin compound 4-(4-(2-(octadecyloxycarbonyl)vinyl)cinnamoylamino)benzoic acid has been found to form a stable monolayer on a water surface and to be successful in fabricating photoreactive Langmuir-Blodgett (LB) films. The photo-oligomerization in LB films have been studied by UV-visible and infrared spectroscopy. The infrared spectroscopy reveals a breaking of hydrogen bonding between the amide groups and a distortion of alkyl chains during the reaction. Furthermore, a correlative two-step kinetics of olefinic groups and the changes in orientation and packing state of the alkyl chains is found. This correlation strongly suggests the dependence of the reaction kinetics on the structural change in the LB films induced by the reaction process itself.