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

Abstract

Abstract 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: α and the radius of gyration ( R g ). The first parameter ( α ) 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.