Vibrational analysis for the all-trans ferroelectric phase conformation of P (VDF) homopolymer and of P(VDF/TrFE) copolymer: A cluster-lattice calculation

Green's functions formalism and transfer matrix method have been used to predict the spectra of all-trans poly(vinylidene fluoride) and the expected changes for poly(vinylidene fluoride/trifluoroethylene) copolymers with the same chain conformation. We find that the use of a simple cluster-lattice calculation, where the impurity cluster is a trifluoroethylene (TrFE) unit immersed in a poly(vinylidene fluoride) P(VDF)] regular chain, can explain the main features observed by infrared and Raman spectroscopy in the frequency range 800 to 1450 cm^?1. The bands associated to vibration modes of regular VDF sequences, like the 880, 1070, 1280, and 1430 cm^?1 ones, are predicted to decrease or even to disappear with increasing TrFE content. The appearance of new peaks at 970, 1300, 1330, and 1410 cm^?1 is also discussed.