We can further illustrate this interpretation by looking at how the scattering of fibril aggregates evolves as the aggregate size increases. This is shown in Figure where the polymers are approximated as cylinders which then aggregate into fibrils of increasing size. The simulated scattering intensity is calculated from the square of the Fourier transform of the cylinders' excess scattering length density. As the fibril diameter increases, the cross-sectional Guinier knee shifts to lower 𝑞 until it is out of range and only contributes its trailing Porod scattering. At the same time a structure factor peak emerges at high 𝑞 due to the cross-sectional packing of the cylinders. This shows how the seemingly different scattering profiles of low and high MW PII-2T can both be explained by fibril aggregation. The small and large fibril scattering in Figure (green and purple) resembles the scattering of low and high MW PII-2T