Spectroscopic Investigations of Polymers and Polymer Surfaces/interfaces.
Vibrational spectroscopy has been applied to analyze the microstructure and adsorption behavior of polymers and molecular amphiphiles. Both high performance polyimide and piezoelectric active poly(vinylidene fluoride-trifluoroethylene) copolymer ultrathin coatings have been analyzed in detail. The degree of anisotropy and structural transformations of the polymers have been characterized. The effects due to the geometric constraint have been observed and understood. The insoluble semifluorinated and hydrogenated amphiphilic monolayer films spread at the air-water interface have been characterized by spectroscopic and surface pressure methods. The structural changes associated with the semifluorinated films have been revealed. The orientation of the molecular chain axes have been calculated quantitatively by the methodology developed in this dissertation. The studies have been extended to the soluble polymeric system. For the first time, polymer adsorption behavior at the air-solution interface has been successfully observed and studied by vibrational spectroscopy. Nearly monodisperse samples of poly(ethylene oxide) of different molecular weight capped with fluorinated ends were used in this work. Microscopic structures of the adsorbed layer have been elucidated in detail and quantitative analysis has been performed to quantify the amount of the polymers adsorbed at the interface. The thermodynamic constants have also been measured by vibrational spectroscopy for the first time. The adsorption behavior has been studied as a function of polymer backbone molecular weight, end group length, and bulk solution concentration. It has found that the shorter end group polymers are much less adsorbed at the interface. It has been determined that the Langmuir adsorption theory is strictly obeyed for the longer end group polymers. Lastly, the structure and morphology of a newly synthesized polypropylene copolymer has been studied by using a variety of techniques, including Raman, wide-angle X-ray scattering, small angle X-ray scattering, differential scanning calorimetry, electron diffraction, and polarized optical microscope. The influences of the non-crystallizable co-units to the crystalline region has been illustrated by spectroscopic and other techniques. It has been found that the copolymer with appearance of the co-units is still capable of crystallizing with monoclinic unit cell with polypropylene, even though the size of the lamella is much smaller. Meanwhile, the spherulitic structure of the polypropylene homopolymer is totally lost.
- Pub Date:
- January 1995
- Chemistry: Polymer; Physics: Condensed Matter