We present a systematic study of the morphology of polyacetylene films, intrinsically oriented during the synthesis using the nematic phase of a liquid crystal as the Ziegler-Natta catalyst solvent. Orientation of the nematic phase, and hence the polymer, was achieved by gravitational flow combined with a vertical 4.7-T magnetic field. Using scanning electron microscopy, polarized Raman and infrared spectroscopies, and four-circle X-ray diffraction, we show that these films consist of distinct well-oriented and unoriented layers, the latter becoming more important for thicker films. Aging the catalyst at a higher temperature leads to a reduction in the polymerization rate and a decrease in the nonoriented fraction. n and p doping of the best films consistently produced parallel conductivities in the range 20 000 S/cm. We propose a model based on polymerization kinetics that explains the existence of different morphologies within a single "film".

The temperature dependence of the Raman scattering from a single crystal of acetanilide (ACN-H) and fully deuterated acetanilide (ACN-D) in the low-frequency (phonon) and C -0 stretching regions was studied. The observed normal behaviour of the frequency shift of the C -0 stretching modes in ACN-D, raises questions concerning several theoretical models previously proposed to explain the peculiar behaviour with temperature of the A , , stretching modes observed in ACN-H. The forms of the low-frequency Raman spectra for ACN-H and ACN-D are very similar, except in the frequency range 70-120 cm-', where an additional mode (denoted D') is seen in the Raman spectrum of ACN-D. A strong temperature dependence of the frequency of this band is observed. The origin of this mode is still undecided.

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Crystalline acetanilide (ACN) is a quasi-one-dimensional anharmonic solid characterized by soft hydrogen-bonded chains of ACN molecules. Recent theoretical interest in the dynamics of ACN stems from the observation of anomalies in the infrared and Raman internal mode spectra at low temperatures. In this context, several models have been discussed, involving, alternatively, Fermi resonances, topological defects or nonlinear localized (Davydov-type) excitations. We present inelastic neutron scattering results on acoustic mode dispersions in deuterated ACN. The measured elastic slopes are found to be strongly anisotropic, consistent with the one-dimensional character of the hydrogen-bonding. The temperature dependence of the longitudinal (LAy) and transverse (TAx) acoustic modes propagating along the chain direction is studied. The observed anharmonic shifts are substantial but not usually so. Furthermore, a systematic search for anomalous elastic or quasi-elastic diffuse scattering fails to yield evidence for structural disorder. On the basis of these results and of optical results on deuterated ACN, we conclude that a Fermi resonance mechanism is most likely to be at the origin of the reported optical anomalies.

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