 Kuhn length

The Kuhn length is the link length of an equivalent long ideal chain with the same contour length and mean squared end-to-end distance. A three-dimensional worm-like chain satisfies $⟨R^2⟩\sim 2l_{p}L$ for $L\gg l_p$, hence $b_K=2l_p$.

The Kuhn length is a concept in polymer physics that describes the effective length of a segment of a polymer chain that behaves as though it is a rigid rod. It is named after the physicist William Kuhn, who contributed to the understanding of polymer behavior. In a simplified model, a polymer chain can be thought of as being composed of many such rigid segments (or "Kuhn segments"), which are connected by flexible linkages.