title: Nanomechanical characterization and molecular mechanism study of nanoparticle reinforced and cross-linked chitosan biopolymer.
abstract: Chitosan (CS) is a biomaterial that offers many sophisticated and innovative applications in the biomedical field owing to its excellent characteristics of biodegradability, biocompatibility and non-toxicity. However, very low mechanical properties of chitosan polymer impose restriction on its further development. Cross-linking and nanoparticle reinforcement are the two possible methods to improve the mechanical properties of chitosan films. In this research, these two methods are adopted individually by using tripolyphosphate as cross-linker and nano-hydroxyapatite as particle reinforcement. The nanomechanical characterizations under static loading conditions are performed on these modified chitosan films. It is observed that nanoparticle reinforcement provided necessary mechanical properties such as ductility and modulus. The mechanisms involved in improvement of mechanical properties due to particle reinforcement are studied by molecular dynamics (MD). Further, improvement in mechanical properties due to combination of particle reinforcement and cross-linking agent with chitosan is investigated. The stress relaxation behavior for all these types of films is characterized under dynamic loading conditions using dynamic mechanical analysis (nanoDMA) experiment. A viscoelastic solid like response is observed for all types of film with modulus relaxing by 3-6% of its initial value. A suitable generalized Maxwell model is fitted with the obtained viscoelastic response of these films. The response to nano-scratch behavior is also studied for particle reinforced composite films.
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, Madras, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Rath
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, Madras, India.
authors.forename: Santhosh
authors.initials: S
authors.lastname: Mathesan
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, Madras, India. Electronic address: pijush@iitm.ac.in.
authors.forename: Pijush
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D002236:Carbohydrate Conformation; D048271:Chitosan / Q000737:chemistry*; D055119:Elastic Modulus; D008422:Materials Testing; D055595:Mechanical Phenomena; D008958:Models, Molecular; D053758:Nanoparticles; D036103:Nanotechnology
chemical_list: D048271:Chitosan
keywords: Biomaterials; Chitosan; NanoDMA; Nanoindentation; Nanomechanical; Nanoscratch