Simulation Study On The Phase Behavior Of Polyelectrolyte Brush In Various Solvents

As an important polymer system for functional surface modification,polyelectrolyte brushes have attracted more and more attention of scientists due to its rich physical connotation and wide application background.By changing the environmental parameters to control the different conformation of polyelectrolyte brush,different modified surfaces can be obtained.Using molecular dynamics method,the behavior of polyelectrolyte brushes grafted on the surface of the hexahedron and the sphere in good solvents and poor solvents is studied.The effects of grafting density and valence of counterions on the behavior of polyelectrolytes brushes in different solvents are studied.Moreover,it is judged whether the curvature had an effect on the phase behavior of polyelectrolyte brushes.In different solvent,it is found that the phase separation behavior and morphology of polyelectrolyte brushes are completely different under different parameters by analyzing the 3-D morphology and 2-D isodensity of hexahedral brushes and spherical brushes,The brush height of hexahedral brushes and spherical brushes as well as the radial distribution functions and correlation functions of monomer and counterion are also studied.The results show that,the increase of the counterion valence intensifies the collapse of polyelectrolyte brushes,strengthens the inter-chain correlation.At the same time,the curvature would also affect the change laws of the brush height and radial distribution function,and affect the correlation of counterions.In addition,the radial distributions of the net charge of hexahedral brushes and spherical brushes are calculated under different solvent conditions,which indicate that the local electric neutrality of the system is affected by the solvent quality,counterion valence and curvature.In order to analyze the phase separation behavior of polyelectrolyte brushes,the role of counterion is studied.Counterions are divided into four ionic states for explaining the phase behavior of polyelectrolyte brushes.And the result show that the counterions play different role under the different curvature,ionic valence as well as solvent quality.