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## Main Question or Discussion Point

I've been trying to calculate the "height" of brush polymers on the surface of colloidal nanoparticles. The reference I'm using is "Polymer brushes" by Milner, Science, 1991, v.251, 905-914. The formula presented here (similar in many other cases I've looked at too) is h ~ N*(w*sigma*a^2)^(1/3).

h is the height [L], w is the excluded volume parameter, sigma is the coverage on the nanoparticle[1/L^2], a is the Kuhn's length [L].

First, can someone explain what the excluded volume parameter is? What are the units of this parameter? Based on this equation, the units are in volume. But when I looked at some other papers, this parameter is dimensionless. In addition, I can't seem to find a good explanation of the excluded volume, or a way of obtaining it theoretically. I need to find a way of finding this for DNA.

Hope someone can help me! Thanks!

h is the height [L], w is the excluded volume parameter, sigma is the coverage on the nanoparticle[1/L^2], a is the Kuhn's length [L].

First, can someone explain what the excluded volume parameter is? What are the units of this parameter? Based on this equation, the units are in volume. But when I looked at some other papers, this parameter is dimensionless. In addition, I can't seem to find a good explanation of the excluded volume, or a way of obtaining it theoretically. I need to find a way of finding this for DNA.

Hope someone can help me! Thanks!