These particles are unusual in that they undergo several dramatic changes in their internal structure at different conditions. Fig. 2 shows the form factors (Fourier-transformed radial density functions, obtained via light scattering) of the particles at different conditions. The form factors at low pH are well-described by the polydisperse core-shell model[1] with additional terms accounting for the heterogeneous distribution of polymer inside the particle[2], $$P(q)=\int\textrm{d}R_{core}f\left(R_{core}\right)\left[3\exp\left(-\frac{q\sigma_{surf}}{2}\right)\frac{\sin\left(qR_{core}\right)-qR_{core}\cos\left(qR_{core}\right)}{\left(qR_{core}\right)^3}\right]^2+\frac{I_{1}}{\left[1+\left(q\xi_{het}\right)^2\right]^2}+I_0,\,\,\,\,\,\,\,\,\,\,(\textrm{Eq.}1)$$ and at high pH by the star polymer model[3], $$P(q)=A_1\int\textrm{d}R_{g}f\left(R_{g}\right)\exp\left[-\frac{1}{3}\left(qR_g\right)^2\right]+\frac{A_2}{\mu q\xi_{blob}}\frac{\sin\left[\mu\arctan\left(q\xi_{blob}\right)\right]}{\left[1+\left(q\xi_{blob}\right)\right]^{\mu/2}}.\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(\textrm{Eq.}2)$$ The integrals include particle polydispersity following a distribution f, in this case a Gaussian. In Eq. 1, the relevant parameters are the radius of the core, the thickness of the surrounding fuzzy shell, the length scale of the heterogeneities, and the intensity amplitudes of the heterogeneous term and constant background. In Eq. 2, the relevant parameters are the radius of gyration, the blob size of the polymer branches inside the particle, μ, a factor related to the internal fractal dimension of the polymer, and the relative amplitudes of the two terms.