Linear Dimensions of Adsorbed Semiflexible Polymers: What can be learned about their persistence length?

Conformations of partially or fully adsorbed semiflexible polymer chains are studied varying both contour length $L$, chain stiffness, $\kappa$, and the strength of the adsorption potential over a wide range. Molecular Dynamics simulations show that partially adsorbed chains (with “tails”, surface attached “trains” and “loops”) are not described by the Kratky-Porod wormlike chain model. The crossover of the persistence length from its three-dimensional value $({\mathrm{\ell }}_p)$ to the enhanced value in two dimensions $(2{\mathrm{\ell }}_p)$ is analyzed, and excluded volume effects are identified for $L\gg {\mathrm{\ell }}_p$. Consequences for the interpretation of experiments are suggested. We verify the prediction that the adsorption threshold scales as ${\mathrm{\ell }}_p^{-1\mathrm{/}3}$.