My system is polymer aggregates formed by two types of polymer chains via hydrogen-bonding in aqueous solution, which is a phase-separated system. I want to figure out the Rg of the aggregates in low-Q region. I tried many models including mass fractal model, Guinier model and Guinier-Porod model, but none of them work well. I uploaded a screenshot of my figure of plot. Can anyone give me some suggestion on it?