In the 2SFC model, we consider that two populations of scatterers are present. The first corresponds to large fibril aggregates while the second corresponds to polymer chains that could be either individually dispersed or consisting of a few chains loosely joined to produce a longer effective length but still maintaining its individual cross-section. Both of these populations are modeled as elongated semiflexible objects denoted by the subscripts 𝑓 and 𝑝 for fiber and polymer, respectively. Additionally, a pseudo-Voigt peak function is used to fit the lamellar structure factor peaks if present. The total model for the scattering intensity is then, apply polydispersity to the fibril radius (and subsequent functions of it) using a Schulz-Zimm distribution. In this case, the specified fiber radius is the mean radius of the distribution (denoted by an overbar) and the parameter 𝜎 𝑓 describes the width of the fibril radius distribution. The relevant terms in equation ( ) then represent averages according to the polydispersity distribution. While polydispersity may also be applied to the polymer radius, we find it unnecessary as the Guinier knee of the polymer radius either quickly approaches a background level or soon becomes dominated by the lamellar peak contribution. For the axial shape function of the semiflexible object Σ 𝑆𝐹𝐶,𝑖 (𝑞; 𝑏 𝑖 , 𝐿 𝑖 ) we use the function developed by Pedersen and Schurtenberger for semiflexible polymers with excluded volume effects with corrections by Chen et al. as implemented by SasView . Because the model primarily describes two separate populations of semiflexible cylinders corresponding to the fiber and polymer we refer to it as the two semiflexible cylinder (2SFC) model in this work. In some cases, if the radius of the fibril aggregates is so large that its Guinier knee is below the experimental 𝑞-range then only the trailing Porod region will be observed at low 𝑞. In this case the polydisperse fibril radius can be set to a sufficiently large value out of range, which effectively makes its contribution equivalent to 𝑞 -4 . Alternatively, if aggregation or network formation is expected but the exact form of the aggregation is unknown then the fibril term in equation ( ) can be replaced with a power law function 𝐴𝑞 -𝑑 where the exponent 𝑑 will describe the shape or dimensionality of the aggregate at that 𝑞-range. In this work we find 𝑑 to be between 3.77 to 4 in the case of large aggregates thus indicating it is indeed specifically due to interfacial Porod scattering.