Polymer Nanocomposites and Biomaterials: From Chemical Cross-linking to 3D Printing

Part 1: Aerogel is an open-celled, microporous, solid foam composed of a network of interconnected structures formed by replacing the solvent in wet gel with air. Integrating the intrinsic mechanical and electrical properties of carbon nanotubes (CNTs) with those of an aerogel provides a new class of material with unique multifunctional properties which may find applications not limited to fuel cells, super capacitors and batteries. I attempt at improving the mechanical integrity by first functionalizing the CNTs with carboxylic (-COOH) groups and subsequently cross-linking the CNTs using diisocyanate to form polyurea-CNT (PUA-CNT) composite aerogels. Mechanical properties of the final PUA-CNT aerogels are presented. Part 2: 3D printing is an additive manufacturing technique capable of creating highly complex and customized structures that are otherwise difficult or impossible to produce using conventional methods such as injection molding. Fused Deposition Modeling (FDM) based on micro-extrusion of thermoplastics is one of the most commonly used methods for 3D printing. The second part of this thesis reports incorporation of carbon nanotubes (CNTs) into PLA with a goal to improve the mechanical properties of the 3D-printed composites. The orientation distribution of CNTs within the printed extrudates has been characterized using X-ray Diffraction (XRD) and scanning electron microscopy (SEM). The effects of process conditions on CNT orientation and the subsequent mechanical properties of fabricated test coupons have been explored. Part 3: Breast cancer is caused by the development of malignant cells in the breast forming a lump or mass called tumor. The malignant cells originate in the lining of the milk glands or ducts of the breast (ductal epithelium) and grow into the surrounding breast tissue. As per the American Cancer Society, in 2015, 1 out of 7 women diagnosed with breast cancer died due to complications arising from the disease. I lay down the foundations for precise and reproducible FDM based 3D bioprinting to help understand the interactions of breast cancer cells with its microenvironment which upon further mathematical modeling may lead to better strategies to treat the disease. Rheology is used as a tool to identify printing parameters of Matrigel®; an extracellular matrix.