To quantify the size and internal structures of the aggregates, the scattering profiles were modeled by using the combination of the following modelsan approach we recently developed: (1) the power law model and/or cylinder model to describe the structure of aggregates in solution at low scattering vector, Q < 0.01 Å -1 (2) the flexible cylinder model for the polymer chains at the intermediate Q region (0.01 Å -1 < Q < 0.1 Å -1 ) where the Porod slopes of polymer chains are close to -1, and (3) the pseudo-Voigt peak at high Q (Q > 0.1 Å -1 ) to fit the structure factor peak which arises from side-chain interaction or lamellar stacking. In Fig. , the contributions of these models are deconvoluted for each SAXS plot and the total fitting curves are plotted on top of the scattering profiles as indicated in Fig. . All relevant fitting parameters obtained from this model fitting approach are summarized in Table . Based on the model fitting, we determine that the Guinier knee at the low Q region around 0.01 Å -1 for PM7 solution corresponds to the cross-sectional radius of the fiber-like aggregates which is equal to 11.4 ± 0.07 nm (error is the fitting error from the model).