Stereo-chemistry controlled mechanical properties of cross-linked Poly (N-isopropyl acrylamide) in aqueous medium using molecular simulations

Poly (N-isopropyl acrylamide) or PNIPAM is one of the most promising hydrogels with diverse applications in tissue engineering and drug delivery due to biocompatibility and tunability of temperature response close to human body. Density of crosslinker primarily limits water absorption of hydrogels below LCST (swollen state). In this work, we use all-atom molecular dynamics to simulate the dynamic bond formation between PNIPAM and its cross-linker to study the influence of stereochemistry and degree of cross-linking (DOC) in aqueous medium in swollen and collapsed states of cross-linked PNIPAM to engineer mechanical properties. Specifically, we obtain radius of gyration (Rg), stress-strain curve, shear modulus (G) and Young's modulus (E) in compression and tension. This study provides a better understanding of customized hydrogel behavior and fine-tuning of its mechanical properties for different applications.