Raman spectra of Langmuir–Blodgett and Langmuir–Schaefer films of polydiacetylene prepared from 10,12-pentacosadiynoic acid

Blue polydiacetylene films were prepared from the Langmuir–Schaefer (LS) and Langmuir–Blodgett (LB) films of the cadmium salt of 10,12-pentacosadiynoic acid, CH₃(CH₂)₁₁CCCC(CH₂)₈COOH, and the CC stretching modes of the Raman spectra of the LS and LB films were observed at 2068 and 2079 cm⁻¹, respectively. These wavenumbers appeared to be sensitive to the packing of polymer chains. Most of the progression bands observed in the range of 1332–1182 cm⁻¹ have been assigned to the CH₂ wagging modes of the all-trans structure of the (CH₂)₁₁CH₃ group.