Theta-solvent brush height
= Theta-solvent brush height
{title2=$H\sim Na(sa^2)^{1/2}$}
In the <Alexander-de Gennes brush model>, a <theta solvent> gives $D\sim ag^{1/2}$. Stacking $N/g$ blobs then gives the displayed height, with mean <polymer> <volume fraction> $\phi\sim(sa^2)^{1/2}$ for segment <volume> $a^3$. Cancellation of the two-segment <excluded volume> does not remove three-segment repulsion or make the crowded layer freely interpenetrable at no cost.