Date of Award

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Polymer and Fiber Science

Advisor

Brown, Philip J

Committee Member

Ballato , John

Committee Member

Cox , Christopher

Committee Member

Luzinov , Igor

Abstract

Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films.
Inorganic nanocrystals doped with optically active rare-earth ions (Tb3+:LaF3) treated with organic ligands were synthesized in water and methanol in order to produce polymethyl methacrylate (PMMA) light-emitting nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were employed to functionalize the surface of Tb3+:LaF3 nanocrystals. We have used infrared spectroscopy, thermal analysis, elemental analysis, dynamic light scattering, rheological measurements and optical spectroscopy to investigate the nanoparticle structure and composition response of ligand-capped nanocrystals under various synthesis parameters. A theoretical interpretation of particle-to-particle interactions also was conducted which supported our study of the potential of agglomeration within the nanoparticle suspensions.
Novel amorphous polymers (e.g. perfluorocyclobutyl aryl ethers, PFCB), which do not exhibit strong C-H vibrations, have been reported to possess excellent optical properties. Little is known of the intrinsic properties of PFCBs (e.g. biphenylvinyl ether, BPVE and hexafluoroisopropylidene vinyl ether, 6F) as well as the behavior of the polymer melt during extrusion. We preformed empirical and experimental thermal and rheological evaluations of BPVE, 6F and polymer nanocomposites of varying loading levels. These studies provide greater understanding of the melt performance of BPVE, 6F and for optically active nanoparticles within PMMA. The data and the use of a fiber melt extrusion modeling package allowed for the construction of viable initial melt fiber extrusion parameters.
Many researchers have focused on the development of polymer light-emitting nanocomposites and novel amorphous polymers for optical applications. I, however, have focused particularly on developing a fundamental understanding of the nanoparticle synthesis. My work concentrates on the surface chemistry of the nanoparticle with an emphasis on the interaction between the surface attached ligand and the polymer matrix. This research will aide in the development of a more optimized and compliant polymeric nanocomposites for optical applications.

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