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Dissertation
Structure-Property-Processing Correlations in Chitosan-Based Porous Hybrid Materials
Doctor of Philosophy (Ph.D.), Drexel University
Nov 2012
DOI:
https://doi.org/10.17918/etd-7557
Abstract
Composites form an important class of materials in our modern world due to their ability to achieve properties that cannot be realized in a single phase material. Taking composite materials to another level of sophistication, the term hybrid materials has been coined and defined; these are materials that are not only a composite of two or more materials, but also possess a custom-designed architecture, which frequently is hierarchical. When fabricating a hybrid material it is therefore essential to have a thorough understanding of the constituent materials, as well as the processing technique through which the materials' desired architecture is created. The objective of this research was to utilize freeze casting, a directional solidification technique, to create highly porous, hierarchically structured composites in which structure and properties could be custom-designed. This was achieved through the solution or slurry composition as well as the processing parameters, such as the freezing rate. The presented research aimed to systematically determine the correlations between processing parameters, composition, structure, and mechanical properties in such freezecast composite scaffolds. The biopolymer chosen for this work was chitosan, a derivative of chitin, which is the second most abundant polysaccharide on earth and thus readably available. The mechanical properties (stiffness, strength, toughness) of chitosan-based materials were influenced through genipin crosslinking, the inclusion of cellulose nanofibers, and the inclusion of mineral particles, namely nanoclay and hydroxyapatite. Through freeze casting, highly porous (>95%) scaffolds with a well aligned pore structure were fabricated from water-based solutions or slurries. From the library of materials and processing parameters established in this work, two materials were chosen and freeze cast in conjunction with different processing parameters in a two-step procedure. The goal of this approach was to mimic natural bone and combine within one scaffold two materials with different structures to simultaneously satisfy two distinct requirements. Through a particularity of the processing technique, the partial melting of solidified material at the interface, a smooth transition between the vastly different structures and materials was achieved. This confirms the hypothesis that hybrid scaffolds with complex shapes can be fabricated to simultaneously provide different functions.
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Details
- Title
- Structure-Property-Processing Correlations in Chitosan-Based Porous Hybrid Materials
- Creators
- Amalie Elizabeth Donius - DU
- Contributors
- Ulrike G. K. Wegst (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) [Historical]; College of Engineering (1970-2026); Drexel University
- Other Identifier
- 7557; 991014632538804721