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Design, synthesize and characterize hierarchically ordered nanofibers (NFSKs) for biomimetic mineralization
Dissertation   Open access

Design, synthesize and characterize hierarchically ordered nanofibers (NFSKs) for biomimetic mineralization

Xi Chen
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2013
DOI:
https://doi.org/10.17918/etd-4168
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Abstract

Biomimetic polymers Electrospinning Materials Science
The seven-level hierarchical structure is essential to the exceptional mechanical properties and biological activities of nature bones. Extensive studied have been devoted to mimicking this complex structure using a synthetic material but limited success has been accomplished. The challenge is to use the soft materials to control the distribution and orientation of minerals. Up to now, only few self-assembled natural and synthetic nanofibers have shown capability to control the orientation of minerals and no synthetic materials are able to achieve control on both distribution and orientation of minerals. In this research, we used a novel structure, nanofiber shish kebabs (NFSKs), to address the challenge. Polycaprolactone (PCL) is selected as the model polymer for the development of NFSKs because of its biocompatibility and semi-crystalline nature. Poly caprolactone and poly acrylic acid (PCL-b-PAA) is synthesized via atomic transfer radical polymerization (ATRP) and used as the secondary polymer to decorate on the nanofiber in the form of single crystal lamellae via polymer crystallization. Anionic nanodomains are formed upon crystallization of PCL segments and self-assembly of lamellar crystals. Utilizing those anionic nanodomains, the distribution and orientation of minerals can be both controlled in a biomimetic mineralization process due to geometrical confinement. The introduction of kebabs onto the nanofiber surface also significantly improves the mechanical properties of NFSK fiber mat by utilizing kebabs as the load-bearing and -transferring agents. Our results provide a new route to achieving exquisite nanoscale structural control in biomimetic hybrid materials.

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