Computer simulation of shearing deformation in polymer systems with polar groups

Abstract

In this work, shear strain modeling in materials consisting of a thin polymer layer (∼15nm), adhesive bonded to a rigid substrate, considered not to be impacted by deformation, was performed. A discrete-continuum model of chains system with a given stiffness with polar groups is developed. The polymer chain was considered in the framework of the persistene model, and the polar groups were based on the lattice model on the tetragonal lattice. It was assumed that the main contribution to the energy of interchain interactions is due to the potential of the polar groups and was calculated using the Metropolis algorithm. The potential interactions between the nearest polar groups of chains included the energy of dipole–dipole interactions (Keesom energy) and the Lennard–Jones potential. It is taken into account that the possible orientations of the polar groups are determined by the average elongation of the chain. Calculations showed that the dependence of free energy on the interchain distance has two minima. The first minimum is characterized by the orientational ordering of the polar groups, the second — by their disordered state. The depth and position of the minima depend on temperature, bending stiffness of the chain, the modulus of the dipole moment of the polar groups and the depth of the potential well in the Lennard–Jones energy. A step-by-step simulation of shear strain in a polymer layer in an orientationally disordered state was carried out. The obtained stress–strain diagrams make it possible to estimate the value of the elastic limit and also to determine the stresses at the points of phase transitions from a disordered to an orientationally ordered state.

Keywords

• polymer systems
• polar group
• shearing deformations
• pvdf
• monte carlo method