Effect of cross-linker and charge on the scattered light by dilute aqueous dispersions of nanogel particles

We report a study on the light scattered by temperature-sensitive poly(N-vinylcaprolactam) (PVCL)-based nanogel particles, with different amounts of cross-linker and charged groups. The scattered light I(q) is measured as a function of the scattering angle at temperatures below and above the volume phase transition temperature (VPTT) of the nanogel particles. I(q) is fitted using an analytical expression with two adjustable parameters: alpha and the radius of gyration (R-g). The first parameter (alpha) provides information on the structure of the external shell, and R-g on the internal mass distribution of the nanogel. Regarding samples with increasing cross-linker amounts, remarkable differences in I(q) are found above the VPTT whereas below the VPTT the differences were not significant. Charged and uncharged nanogels also show noticeable discrepancies between the swollen and the collapsed state. The I(q) curves of shrunken uncharged nanogel particles are similar to those of uniform spheres. In the case of charged nanogels, the I(q) curves reveal that the core shell structure of the particle persists in both the swollen state and the shrunken state. (C) 2015 Elsevier B.V. All rights reserved.