The molecular structure of ultradrawn films of polyethylene has been studied with a combination of different techniques of vibrational spectroscopy, namely attenuated total reflection at different angles of incidence (thus doing optical microtoming), infra-red absorption and Raman scattering in various geometries and polarizations. The experimental results are interpreted on the basis of the theoretical concepts of the lattice dynamics of ordered and disordered polymethylene systems previously worked out. A gradient of molecular and crystalline structures is found from the surface into the core. The skin is highly orthorhombic; moving inside the film, both monoclinic and orthorhombic lattices coexist. Moreover, in the core a new phase with 'isolated' trans-planar sequences is observed. Various kinds of collective and oriented or isolated conformational disorder are identified. From the experimental data collected, a molecular model is proposed for the process of orientation during drawing. A problem of general relevance in Raman scattering of polymers is presented by the fact that the scattering observed arises only from the upper skin of the sample.
Посилання на статтю:
Structure of the skin and core of ultradrawn polyethylene films by vibrational spectroscopy / E. Agosti* and G. Zerbi // Polymer. – 1992. – Vol 33. – P. 4219-4229.
