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CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES

Cudjoe, Elvis
http://rave.ohiolink.edu/etdc/view?acc_num=case1497444919191893

Abstract Details

2017, Doctor of Philosophy, Case Western Reserve University, Macromolecular Science and Engineering.
This dissertation focuses on the design and fabrication of different cellulose nanocrystals (CNCs) polymer nanocomposites, with the goal of impacting the structure-property relationship between CNCs and the CNCs/matrix interactions through the surface functionalization of the CNCs with different chemical functional groups. Chapters 2-4 focus on how CNCs from sea tunicates (t-CNCs) functionalized with different chemical moieties affect the mechanical properties of the resulting nanocomposite. First (Chapter 2), t-CNCs were functionalized with lower critical solution temperature (LCST) responsive poly(oligoethylene glycol)monomethyl ether (meth)acrylates, which were incorporated into a poly(vinyl acetate) (PVAc) matrix to create reversible, thermal stiffening nanocomposites. When placed in water below the LCST the nanocomposites are soft, however, when placed in water above the LCST the nanocomposites stiffened as a result of the collapse of the grafted polymer chains allowing the engagement of t-CNCs nanorods. Secondly (Chapter 3), t-CNCs were used as fillers by functionalizing the surface with carboxylic acid moieties which aided in its dispersion in solvents such as N-methyl-2-pyyrolidone (NMP). The dispersion was further used in the synthesis of polyimide aerogels which demonstrated improved physical and mechanical properties as well as thermal stability with the incorporation of t-CNCs as a filler. Lastly (Chapter 4), by functionalizing the surface of t-CNCs with carboxylic acid and amine moieties, t-CNCs were demonstrated to be electrically active. Applying electric current across aqueous solutions of such t-CNCs, resulted in the fabrication of aligned micron-sized t-CNC fibers. Electrically aligned fiber composites with collagen were fabricated by matching the carboxylic acid/amine ratio of t-CNC and collagen. These aligned nanocomposite fibers demonstrated improved mechanical properties with higher contents of t-CNCs. Chapter 5 highlights the isolation of CNCs from a new scalable source of CNCs, Miscanthus x. Giganteus (MxG), and how properties of CNCs from this new source compares to current biosources for CNCs such as wood. Chapter 6 demonstrates the use of CNCs from MxG in a cross-linked polymer nanocomposite adhesive and how its adhesive properties are affected. MxG-CNCs were isolated from stalks of MxG through base hydrolysis, bleaching and acid hydrolysis. After acid hydrolysis, MxG-CNCs showed a relatively high crystallinity (>90%) and high aspect ratios of 60-70 confirmed by Transmission Electron Microscopy (TEM). Comparing mechanical properties of PVAc nanocomposites containing CNCs from wood to CNCs from MxG showed at least as good if not slightly better properties for MxG-CNC/PVAc nanocomposites. Following the successful isolation of MxG-CNCs, a new class of MxG-CNC related nanocomposite adhesive was designed. The surface of MxG-CNCs was functionalized with a thiol group (MxG-CNC-SH) which were used as a cross-linking moiety in a polydisulfide network. The utility of the MxG-CNC-SH nanocomposite adhesive was demonstrated to bond to different substrates such as hydrophilic and hydrophobic glass slides and metal, with the high surface energy substrates (metal and hydrophilic glass slides) exhibiting stronger adhesive shear strength with higher MxG-CNC content. On the other hand, bonding to low surface energy hydrophobic glass showed a maximum adhesive shear strength with composites that contained only 1 wt% MxG-CNC-SH.
Stuart Rowan (Committee Chair)
LaShanda Korley (Committee Member)
David Schiraldi (Committee Member)
Ozan Akkus (Committee Member)
260 p.
Chemistry; Materials Science; Polymer Chemistry; Polymers
Cellulose Nanocrystals; Nancomposites; Stimuli Responsive; Adhesives; Aerogels; Miscanthus Giganteus; Collagen

Recommended Citations

Citations

  • Cudjoe, E. (2017). CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1497444919191893

    APA Style (7th edition)

  • Cudjoe, Elvis. CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES . 2017. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1497444919191893.

    MLA Style (8th edition)

  • Cudjoe, Elvis. "CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES ." Doctoral dissertation, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1497444919191893

    Chicago Manual of Style (17th edition)

case1497444919191893
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© 2017, some rights reserved.Creative Commons License CELLULOSE NANOCRYSTALS AND RELATED POLYMER NANOCOMPOSITES by Elvis Cudjoe is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.