THERMO-MECHANICAL CHARACTERISATION OF􀀍h-BN􀀍 REINFORCED􀀍PEGDA􀀍HYDROGEL􀀍FOR􀀍BIOMEDICAL􀀍 APPLICATIONS

Abstract

Hydrogel is a three-dimensional cross-linked hydrophilic network of polymer chains that can imbibe a large amount of water up to 99% of its dry weight. Due to its unique characteristics and biocompatibility, hydrogels have applications in diverse fields, including tissue engineering, drug delivery, biosensors, and agriculture. Even though hydrogels are emerging as potential candidates for replacing artificial organs and treating issues relevant to tissues, lower thermo-mechanical strength still poses challenges in replacing conventionally used materials. Hydrogels can be reinforced with organic, inorganic, and metal-based nanofillers to improve their mechanical strength and thermal conductivity. Many researchers have reported the tunable properties of PEGDA hydrogel by varying either molecular weight (low-high) or incorporating nanoparticles. Due to dispersibility issues, many applications replace organic nanofillers (CNT, graphene) with inorganic nanofillers (h-BN). Among inorganic nanofillers, hexagonal boron nitride nanofillers (h-BN) have comparable thermo-mechanical properties to organic nanofillers. They are proposed as a potential candidate for reinforcement to enhance the strength of PEGDA hydrogels. In this thesis work, a combined experimental and atomistic approach (molecular dynamics simulations) was employed to explore the thermo-mechanical properties of the nanocompositebased PEGDA hydrogel. The MD-based simulations help in capturing the deformation governing mechanism at localised scale, whereas experiments help in characterising the mechanical behaviour at the macro scale. The MD-based simulations give insight into scrutinizing the behavior of polymer chains and their entanglement and shed light on nanoscale phenomena that are usually inaccessible through experiments alone. The nonreactive force field (OPLS-UA), TIP3P, and Tersoff are employed to simulate the polymer chain, water molecules, and h-BN nanosheets, respectively, while cross interactions between the polymer and h-BN were modeled using the non-bonded LJ force field. In order to characterize the thermal and mechanical response of neat and h-BN reinforced nanocomposite PEGDA hydrogels, the samples were first synthesized with different water content in conjunction with different weight contributions of h-BN nanoparticles in the range of 0.25 to 1 weight percentage of PEGDA.