| Abstract
| - The geometric characteristics of nanogel particles in aqueous solutions were studied by determining theirratios of radius of gyration (mean-square radius; Rg) to hydrodynamic radius (Rh), Rg/Rh, derived from staticlight scattering and dynamic light scattering experiments, respectively. The various nanogel samples studiedincluded ones composed of lightly cross-linked N-isopropylacrylamide (NIPA) polymer, NIPA-based anionicor cationic copolymers, and amphoteric terpolymers. Polyelectrolyte complexes between anionic or cationicnanogels and oppositely charged polyions or nanogels having opposite charges were also studied. Most NIPAand NIPA-based polyelectrolyte nanogels in a swollen state had Rg/Rh values >0.775, which is the theoreticallypredicted value for a solid sphere. In a collapsed state, one may expect nanogel particles to be spherical inshape; however, this was not the case for a variety of nanogel samples, either with or without charges. Thesedata were consistent with the idea that the surfaces of these nanogel particles were decorated with attacheddangling chains. The Rg/Rh data from polyelectrolyte−nanogel complexes, however, indicated differentstructures from this. It was found that most of the polyelectrolyte−nanogel complex particles had Rg/Rh ∼0.775. This suggested that the complexed nanogel particles were spherical in shape and that there were nodangling surface chains.
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