Abstract
Polymer brush has already been widely used to modify the surface property while there is little research about the interaction between polymer-bearing surfaces at atomic scale. The complex multibody interaction among atoms makes it difficult to characterize the microscopic dynamic process using continuum mechanics. Molecular dynamics method has already been justified to be an efficient theoretical toolkit for investigating the complex dynamic behavior at atomic scale. Friction interface modified by polymer brush in confined space and the corresponding effect are investigated using parallel molecular dynamics simulation method. It is shown that some chains stretch along the direction of flow while others shrink inside the brush resulted by the normal compression. The normal force quickly increases when two end-grafted surfaces are brought into contact while the shear force keeps smaller under the same circumstances. The friction coefficient between polymer brush grafted surfaces is gradually decreased with the increasing of sliding speed which means polymer brush can dramatically improve working conditions. The components of the chains prefer to repel each other as much as possible and weaken interactions among them by stretching away and thus reducing the entropy of the chain.
Highlights
Surface modified by polymer brush interacting with other substances has already become of great importance because of the induced new function such as surface hydrophobicity, biocompatibility, conductivity, surface hardness, surface roughness, adhesion, lubrication, and antistatic property
Polymer brushes can be generated under different conditions: the molecules at the end of the long chain adhere on surface; the molecules at the end of the long chain adhere on two surfaces; the terminal molecules of long chain linked with another polymer molecule with lots of attachment
MATERIALS AND METHODS Molecular dynamics (MD) is a computer simulation method for studying the physical property of ensemble composed of atoms and molecules, the atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamical evolution of the ensemble
Summary
Surface modified by polymer brush interacting with other substances has already become of great importance because of the induced new function such as surface hydrophobicity, biocompatibility, conductivity, surface hardness, surface roughness, adhesion, lubrication, and antistatic property. The shape and size of polymer brush are sensitive to individual interactions among chains and environment. It is the ability of undergoing larger profile changes that makes them being one of the construction unit of nanotechnology. The height of polymer brush consists of end-anchored polymer chain far from the matrix in given solvent will larger than that of the end-to-end distance of the same non-grafted chain in the same solvent. When polymer molecules grafted to surface, the segments of the individual chains cannot feel each other and will behave like single chain if the distance between two anchoring sites larger than the size of the surface attached polymers
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