A Novel Approach to Modify Chitosan Nanocrystals via Polymer Grafting
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Authors
Ramirez Foyo, Carlos Antonio
Date
2024-09-18
Type
thesis
Language
eng
Keyword
chitosan nanocrystals , surface modification , polymer grafting , nitroxide-mediated polymerization
Alternative Title
Abstract
Chitosan nanocrystals (ChsNCs) are bio-based nanomaterials obtained from chitin, the second most abundant natural polymer in the world. The mechanical properties of ChsNCs, such as high elastic modulus and mechanical strength, make them suitable for implementation in the development of polymer-based nanocomposites. Implementing ChsNCs as a sustainable material in commercial applications could be an opportunity to repurpose crustacean waste, which usually contributes to environmental pollution.
Although the mechanical properties of ChsNCs make them ideal for reinforcing polymer-based composites, the surface of ChsNCs is inherently hydrophilic and incompatible with hydrophobic polymer matrices, hindering the integration of ChsNCs in the development of composite materials. The surface of ChsNCs has been previously modified with various small molecules and polymers to increase the hydrophobicity of the material. However, nitroxide-mediated polymerization (NMP) has not been used for the polymer grafting on the surface of ChsNCs. In this work, a new approach to modify the surface of ChsNCs with well-defined synthetic polymers via NMP and the “grafting to” approach was developed to increase the range of applications of ChsNCs. In order to achieve this polymer graft modification, the surface of ChsNCs was initially modified with glycidyl methacrylate (GMA), obtaining a reactive surface for grafting the synthesized polymers. Then, the functionalized ChsNCs-g-GMA were modified with sodium dodecylbenzene sulfonate (SDBS) to facilitate the polymer grafting reaction in organic media. Polystyrene (PS) and poly (methyl methacrylate) (PMMA) were synthesized via NMP, which allowed a well-controlled polymerization and low dispersity. Finally, the surface of the functionalized ChsNCs-SDBS-g-GMA was modified with PS and PMMA via “grafting to,” offering a strategy to tailor the surface properties of ChsNCs. The surface modification of ChsNCs with PS and PMMA was confirmed by FT-IR, 1H NMR, and TGA. The results obtained in this work demonstrate that this approach can successfully modify the surface of ChsNCs using well-defined synthetic polymers, potentially increasing the implementation of the polymer-modified ChsNCs as a reinforcement material in sustainable nanocomposites.
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Attribution-NonCommercial-NoDerivatives 4.0 International
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-NonCommercial-NoDerivatives 4.0 International