Estudo da influência da hidratação na resposta elástica do polímero polietilenoglicol

Abstract

In this dissertation, we investigate the elastic properties of the hydrophilic polymer polyethylene glycol (PEG) using molecular dynamics simulations implemented in the LAMMPS software. The study focused on the elastic response of PEG when subjected to stretching forces applied to its ends, analyzing its behavior in two distinct environments: immersed in water and in a vacuum. For each scenario, a three-dimensional simulation box was configured, with the water reservoir prepared using the TIP4P model and the PEG set up with the CHARMM force field. The simulations take into account the specific intermolecular interactions of each environment, as well as standard conditions of temperature and pressure. During the thermalization phase, it was observed that the temperature and water density reached a steady state, allowing the proper equilibration of the PEG molecule in the system. After this equilibrium was achieved, stretching forces were applied, initially constant and later varying linearly, and the system's response was monitored over time. The results show that while the end-to-end distance of PEG behaves similarly in both environments over long timescales, there are significant differences in the initial stages, especially in temperature variation, with the vacuum exhibiting greater thermal instability. We conclude that water, as a good solvent, thermally stabilizes PEG and influences its conformation, in contrast to the vacuum, where these stabilizing interactions are absent. This work contributes to the understanding of the mechanics of hydrophilic polymers like PEG under different environmental conditions, with important implications for the development of biomedical materials and controlled drug delivery systems.