3 Preparation of nanoparticle-based polymer composites M. Subbir Parvej a,* , M. Ishak Khan b,* , and M. Khalid Hossain c,d,* a North Dakota State University, Fargo, ND, United States, b University of Pennsylvania, Philadelphia, PA, United States, c Kyushu University, Fukuoka, Japan, d Bangladesh Atomic Energy Commission, Dhaka, Bangladesh 3.1 Introduction Over the last few decades, multiphase solid materials have grown interested due to their diverse applications in various fields. The 21st century has observed and been observing an increasing demand for superior materials from the perspective of higher mechanical properties, excellent thermal properties, and convenience methodologies for their production. Therefore, materials with nanostructures have been appealing due to their robustness and reliability with appropriate properties and behavior in diver- sified industry scenarios (Kruis, Fissan, & Peled, 1998). The objectives of producing nanocomposites can vary from obtaining mechanical properties such as higher Young’s modulus, stiffness, tensile strength (while not sacrificing other properties such as tough- ness); greater thermal properties such as higher glass transition temperature; or specific electric, optical (Hossain et al., 2021), or optometric properties such as higher conduc- tivity for capacitor or superconduction applications, higher refractive index for greater visibility, etc. Moreover, sometimes they are produced to obtain other characteristics according to specific needs, such as flame retardancy, chemical inertness, etc. (Kumar & Krishnamoorti, 2010). Currently, nanocomposites are being used in automo- tive parts, medical device production, thin-film industries, aerospace, biomedical appli- cations such as tissue engineering, cellular therapeutics, building of drug delivery mechanism (Hossen et al., 2019; Mahfuz, Hossain, Khan, Hossain, & Anik, 2022), etc. In general, the production of nanocomposites means inserting nanostructures inside a matrix material. The material properties are not only dependent on the organization, orientation, and properties of the individual nanostructure properties, but also the interaction with the matrix material and the matrix attribute itself. As they satisfy the definition, nanocomposites can include colloids, copolymers, and material con- taining a gel-like network. Although nanocomposites can occur naturally in bone-like materials, the constitu- tion of gel-like materials, organo-clays, or polymer-clay composites started in the 1950s and flourished in the 1970s. In general, the production of nanocomposites con- sists of reinforcement by nanofibers or sheet-like structures. * The authors contributed equally to this chapter. Nanoparticle-Based Polymer Composites. https://doi.org/10.1016/B978-0-12-824272-8.00013-0 Copyright © 2022 Elsevier Ltd. All rights reserved.