The comonomer effect on the structures of poly(vinylidene fluoride-hexafluoropropylene) P(VDF-HFP) copolymers was analyzed by Raman spectroscopy. The HFP content of these copolymers varies from 5% to 15%. Because of steric interactions involving the bulky HFP comonomers, the predominant chain conformation has extensively more gauche conformers in comparison to the neat PVDF Based on both experimental and simulation studies, specific spectroscopic features in the 400-900 cm(-1) region have been identified that are characteristic of irregular chain conformations elucidating the perturbing effect of HFP on the equilibrium chain statistics of PVDF in the amorphous phase. In addition, these spectroscopic features were revealed to be extremely sensitive to the relative placements of the CF3 units with respect to other fluorine atoms along the chain. (c) 2008 Elsevier Ltd. All rights reserved.