Modeling the Structure and Antifouling Properties of a Polymer Brush of Grafted Comb-Polymers

Numerical self-consistent field theory is used to study the structural characteristics of a polymer brush consisting of end-grafted comb-polymers. A comb-polymer brush is shown to retain the parabolic density profile characteristic of the unbranched brush. Increasing either the number of branches or the length of the side-chains leads to an increase in the height (H) of the brush. This is partly because of the branched structure: it is more favorable to stretch the polymer backbone, while leaving the side-chains almost unstretched. The other reason for the increased stretching is simply because of the extra polymer in the brush due to the branches. We find that it does not matter how the side-chains are distributed along the backbone for the predicted density profile; it is only the total amount of polymer in the side-chains that is important. The effect of branching on the brush height can be captured in a simple scaling law: H ∼ Nb(NT/Nb)2/3, where Nb is the chain length of the polymer backbone, NT is the total chain length, thus including the side-chains, and their ratio NT/Nb is a measure for the amount of branching. The structure of the branched brush is less suitable for keeping away small particles from the grafted interface. It is, however, a good way of increasing the polymer density, and thus its antifouling properties, when the grafting density of the brush is limited.