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01: Bionanocomposites with controlled properties
This research is an NSF and DOE funded project where Akpalu is the principal investigator.
Research Goal: Build a robust molecular-level understanding of the influence of structure and morphology on mechanical properties of poly(hydroxyalkanoate)-based nanocomposites.
As a family of polymers, PHAs have functional properties sufficient to replace a significant portion of the 300 billion pounds of petroleum-based amorphous and semicrystalline polymers currently in use for packaging, adhesive, and coating applications. Because crystal formation depends on the molecular structure of polymer chains, we are concerned with integrating scattering (light, X-rays and neutrons), microscopy (atomic force, optical, electron), and modeling to build a quantitative description of the interplay between the molecular structure of polymer chains and the final morphology that impacts properties.
Structure-process relationships being developed under the DOE grant are being used to build useful structure-property relationships under the NSF grant. The properties of interest are the overall stress-strain behavior, Young’s modulus, yield strength, and toughness. Towards this goal, we are using structural and thermodynamic information from X-rays (USAXS, SAXS, WAXS) and my unique light scattering capabilities to generate scattering spectra that span atomistic to micrometer length scales. These spectra will be used to establish connectivity relationships between structure, morphology, and mechanical properties.
We are using a two-fold approach to establish these relationships. The first approach is to build analytical structure-morphology-property connectivity relationships using a continuous structural and morphological spectrum constructed from X-ray (spectra spanning the atomistic to several hundred nanometers) and light scattering (0.5 to 50 microns) measurements. The goal here is to devise computational, analytical and/or scaling relationships that capture the unique influence of crystallization conditions and mechanical properties on the polymer structure and morphology at different size scales. The second approach is a collaborative effort with the Martin group (Chemical & Biological Engineering). Here, we are using Network Component Analysis (NCA), to build structure-process and structure-property connectivity relationships because of unique properties of the NCA approach. Given these properties, our NCA approach utilizes scattering data and materials knowledge as a basis for extracting property information present in the scattering profiles.
We anticipate that this work can provide a fresh perspective and potentially ground-breaking approach to directed materials design and fabrication.
Related Publications
- Y. A. Akpalu, P. Peng, “Probing the melt miscibility of a commercial polyolefin blend by small-angle light scattering”, Materials and Manufacturing Processes, 2007, accepted.
- Akpalu, Y. A., “Towards polyethylene nanocomposites with controlled properties”, Polyolefin Composites Book”, D. Nwabunma & T. Kyu (Eds.), Wiley, 2007, Chapter 13, in press.*
- Xiao Z, Li Y, Ma D, Schadler LS, Akpalu YA, “Probing the use
of Small-Angle Light Scattering for Characterizing Structure of Titanium
Dioxide/Low Density Polyethylene Nanocomposites”, Journal of Polymer
Science Polymer Physics Edition 2006, 44:1084-1095.
- Dongling
Ma, Yvonne A. Akpalu, Ying Li, Richard W. Siegel and Linda S. Schadler, “Effect
of Titania Nanoparticles on the Morphology of Low Density Polyethylene”,
Journal of Polymer Science Part B Polymer Physics, 2005, 43, 488-497.
- Ying
Li and Yvonne A. Akpalu, “Probing the melting behavior of a
homogeneous ethylene/1-hexene copolymer by small-angle light scattering”, Macromolecules,
2004, 37, 7265-7277.
- Yvonne A. Akpalu* and Youyu Lin, “Multivariable Structural Characterization of Semicrystalline Polymer Blends by Small-Angle Light Scattering”, Journal of Polymer Science Polymer Physics Edition, 2002, 40, 2714 – 2727.
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