title: Molecular mechanisms in deformation of cross-linked hydrogel nanocomposite.
abstract: The self-folding behavior in response to external stimuli observed in hydrogels is potentially used in biomedical applications. However, the use of hydrogels is limited because of its reduced mechanical properties. These properties are enhanced when the hydrogels are cross-linked and reinforced with nanoparticles. In this work, molecular dynamics (MD) simulation is applied to perform uniaxial tension and pull out tests to understand the mechanism contributing towards the enhanced mechanical properties. Also, nanomechanical characterization is performed using quasi static nanoindentation experiments to determine the Young's modulus of hydrogels in the presence of nanoparticles. The stress-strain responses for chitosan (CS), chitosan reinforced with hydroxyapatite (HAP) and cross-linked chitosan are obtained from uniaxial tension test. It is observed that the Young's modulus and maximum stress increase as the HAP content increases and also with cross-linking process. Load displacement plot from pullout test is compared for uncross-linked and cross-linked chitosan chains on hydroxyapatite surface. MD simulation reveals that the variation in the dihedral conformation of chitosan chains and the evolution of internal structural variables are associated with mechanical properties. Additional results reveal that the formation of hydrogen bonds and electrostatic interactions is responsible for the above variations in different systems.
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Mathesan
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600 036, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Rath
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600 036, India. Electronic address: pijush@iitm.ac.in.
authors.forename: Pijush
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry*; D020100:Hydrogels / Q000138:chemical synthesis / Q000737:chemistry; D008956:Models, Chemical; D053761:Nanocomposites / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D020100:Hydrogels
keywords: Cross-linked hydrogel; Deformation mechanism; Hydrogel; Molecular dynamics; Nanocomposite