Predicting Chain Dimensions of Semiflexible Polymers from Dihedral Potentials

We develop a numerical and an analytical approach to estimate the persistence length l_p and mean-square end-to-end distance ⟨R²⟩ of complex semiflexible polymers. Numerically, l_p and ⟨R²⟩ are determined by averaging a large set of single chain conformations with the correct dihedral angle distributions p(ϕ_i). Analytically, l_p and ⟨R²⟩ are extracted from the tangent–tangent correlation function. We apply both approaches to two semiflexible conjugated polymers, poly­(3-hexylthiophene) (P3HT) and poly­((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis­(thiophen-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl) (PFTBT). Results obtained via the two methods agree for polymers with any degree of polymerization N. Our methods can be applied to any semiflexible polymers with any number of distinct moieties.