Analysis of the normal forces between surfaces bearing polymer brushes and its lubricity properties

CENCHA, LUISA G.; REMCO TUINIER; CATARINA CARVAHLO ESTEVES

Noordwijk

Conferencia; Coatings Science International 2019 Conference; 2019

In recent years an increased number of experimental andtheoretical studies appeared regarding the structure-properties relation of anchoredpolymers. A key property of interest is the lubricity of surfaces bearingpolymer brushes. It is of great interest to understand how to tune frictioncoefficients and how to apply this knowledge for the design of low frictionsurfaces. In this work self-consistent mean-field computations have been performedto study the normal forces arising when a polymer brush is confined between twosolid surfaces, or when two opposite polymer brushes interact with each other. Theaim is to gain insights on the underlying mechanisms affecting the normal forces,and as a result, affecting the friction coefficients of the surfaces bearingthe brushes. In order to compare with experimental results from literature, twokinds of attached polymer chains have been studied: free and looped anchoredpolymers, having one and two ends attached to a solid surface, respectively.  Our results shows that the necessary forcesto compress looped brushes are bigger than in the case of free brushes havingcomparable chain lengths and grafting densities. This is in agreement withprevious experimental results of the Young modulus and with the normal trendsobserved: anchored polymers which are looped and cyclic exhibit lower friction coefficientsthan free ones.