GOALI: Structural Studies of Orientational Development in Polymers using Real-Time Non-Invasive Spectroscopic Methods

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9812088 Rabolt This GOALI award between the University of Delaware and DuPont, co-funded by the Division of Materials Research and the Office of Multidisciplinary Activities of the Directorate for Mathematical and Physical Sciences, is focused on non-invasive analysis of polymers during actual processing. Vibrational spectroscopy has the potential to act as a non-invasive probe which is sensitive to chemical, conformational, crystal and morphological structure as well as molecular orientation. Both infrared spectroscopy and Raman scattering will be utilized to examine polymeric films and fibers because these spectroscopic probes are sensitive to the development of backbone and side chain orientation and unlike x-ray diffraction do not require a coherent stacking of crystalline regions in order to provide structural information. As a spectroscopic technique, Raman scattering is non-invasive, capable of differentiating between conformers, and can provide information on chain orientation when the directional nature of polarized Raman scattering is utilized. An additional advantage of Raman scattering is the ease of sampling. Since it is a scattering technique, spectra can be obtained on fiber bundles as well as individual filaments. If instead, studies of thin films are of interest, then infrared (IR) absorption spectroscopy is the choice since the absorption cross section is 5-6 orders of magnitude greater than the scattering cross section for the same normal mode and the flat film geometry is ideally suited for IR studies. Hence both IR and Raman studies will be conducted in the "real- time" domain as structure and orientation develop in poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and poly(ethylene napthalate) (PEN) during deformation and/or heating. %%% The use of polymeric materials is extremely widespread in our lives today. The value that these materials provide to the end user is directly related to the various properties, e.g., elasticity, toughness, and strength, that they exhibit. Infrared spectroscopy and Raman scattering are important analytical techniques for the non-destructive evaluation of the development of orientation and order in polymeric materials. Traditionally studies are done either before or after a polymer is processed into its final form (e.g., soda bottle) but this fails to provide an insight into the evolution of structural development as it happens. The proposed approach outlined here will allow for the real-time measurement of local order and orientation as materials are processed. The application of these spectroscopic techniques to polymers will provide important information on structure/property relationships which develop during processing and will allow us to design new manufacturing protocols to optimize polymer performance. ***