Interpenetration and Lubrication of Responsive Polydisperse Brushes: Theory and Simulations

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Polymer brushes are commonly used for permanent surface modification to mediate the stability of colloidal dispersions, provide anti-fouling properties and protect the system from degradation. Brush-like structures in combination with the synovial fluid provide very low friction in mammalian joints and have important applications as lubricants in machine parts and in artificial hip and knee joints. Brushes can also act as smart stimuli-responsive materials that change surface properties reversibly or act as sensors. Here we propose to use brushes formed by adsorption-active chains to control the compressional and lubricating properties of brush-modified surfaces in response to changing the temperature and/or solvent composition. Polydispersity is an inherent property of real polymer systems, which is normally fixed by the synthesis/preparation techniques, and brush properties are affected by it. We will demonstrate that it can be reversibly modified, together with the effective grafting density by varying the monomer-surface affinity, through a microphase segregation mechanism.