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)(11)-C C-C C-(CH2)(8)COOH, and the C C 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)(11)CH3 group. (C) 2007 Elsevier B.V. All rights reserved.