= Good-solvent force-extension scaling
{title2=$R\sim Na(fa/k_BT)^{2/3}$}
For a long flexible <polymer> in a <good solvent>, a <tensile blob> of size $\xi_t\sim k_BT/f$ contains $g\sim(\xi_t/a)^{1/\nu}$ statistical segments. Aligning $N/g$ blobs gives $R\sim(N/g)\xi_t=Na(fa/k_BT)^{1/\nu-1}$. The three-dimensional <Flory approximation> $\nu=3/5$ gives the displayed power. The regime requires $a\ll\xi_t\ll aN^\nu$: below its <force> range the coil has ordinary <linear response>, and above it finite link extension matters. Numerical amplitudes depend on <solvent> quality and segment conventions.<Excluded Volume Effects and Stretched Polymer Chains by Philip Alan Pincus>[abstract and section I, p. 386]{ref}
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