Interpenetration between a polymer brush and a polymer star at thermal equilibrium: A theoretical approach

Abstract

By means of the density functional theory framework I tackle the long-standing problem of a polymer star interpenetrating with a polymer brush at thermal equilibrium. Remarkably, the star is repelled to the outside of the brush once it sucks into the brush. It turns out that there could be a highly fluctuating region at the brush edge. The highly fluctuating region would be responsible for discontinuous absoption transitions by brushes. However, up to an small interpenetration length, below which asphericity of the star is maintained, the star gets collapsed by sucking more and more into the brush.

Polymer brush bilayer under non-equilibrium shear inversion: An MD simulation approach

“…The simulations run for revealing that their simulations are wrong. In general, I conclude that polymer brush bilayers are not good candidate for lubrication as they show shear thickening in stationary shear motion [20][21][22][23] but they do not show any overshoot in the shear inversion which is good thing and I believe this is the reason that nature has chosen to use this system in the synovial joints. Therefore, there is no need to study other versions of polymer brush bilayers like charge effects or macro-molecular inclusions to suppress the overshoot in the shear stress.…”

Polymer brush bilayer under stationary shear motion at linear response regime: A theoretical approach

“…It means that the actual power law of the wall distance is Π s ∼ D − 3 and µ ∼ D . The chain extensions at low shear are given as follows, 20 the above relations say that as long as the Weissenberg number does not exceed unity the chain extensions remain the same as equilibrium conditions and they do not become a function of the Weissenberg number.…”

“…Now let us consider brushes that are grafted onto the flat plates and are suspended in a solvent. The equation of state of a PBB has been calculated 20 and it is given as follows, where a is the Kuhn length or monomer size, b the second Virial coefficient, N the degree of polymerization, σ the grafting density and I have introduced the following volumes for the sake of brevity, …”

A review of recent theoretical advances in polymer brushes

“…2 There have been many theoretical, numerical and experimental works on polymer brushes. 5,[9][10][11][12][13][14][15][16][17][18][24][25][26][27][28][29][30] Polymer brush bilayers are two opposing brush covered surfaces where the top and bottom chains interpenetrate moderately. 2 Polymer brush bilayers could be found in many biological systems, for instance, as Glycol in the outside of cells and as aggregan in the synovial joint of mammals.…”