Characterization of structural transformations with vibrational spectroscopy
The work presented in this thesis applies primarily the techniques of Raman and infrared spectroscopy to characterize the structural transformations in polymers. An overview of the problems studied is given in Chapter 1. Particular emphasis is given to mainly syndiotactic polypropylene structural transformations influenced by configurational defects (Chapter 2), and thermal history and mechanical deformation (Chapter 3). In Chapter 4, the influence of a confining surface in the structural transformation of poly(dimethyl siloxane) Langmuir films at the air-water interface is characterized.
Using a combination of Raman spectroscopy, and normal coordinate analysis of both ordered and disordered chains, it was possible to relate the Raman spectrum to the amorphous phase and ordered phase structures. With this relationship, it was possible to directly relate the Raman spectrum to the population of meso(isotactic) defects in mainly syndiotactic polypropylene. In addition, time, temperature, and mechanical stretching-dependent transformations were characterized.
With external reflectance infrared spectroscopy, it was possible to characterize chain conformation and the local environment of the polymer backbone. Dependence of band intensity and frequency was related to the average segmental orientation and the proximity of the water surface.