| Abstract
| - Thermosensitive polymers such as poly(N-isopropylacrylamide) (PNIPAM) have a lower critical solutiontemperature in water in a temperature range between 32 and 35 °C. Micro- and macrogels of such polymersshow a temperature-controlled reversible swelling behavior. Therefore, they are of great interest for avariety of applications (e.g., the controlled drug delivery and accessibility of enzymes). Up to now such gelswere prepared by covalent cross-linking. A new and promising route for the preparation of microgels downto the nanometer scale consists of the formation of polyelectrolyte complex particles between ionicallymodified thermosensitive polymers. The formation, structure, and temperature behavior of complexesbetween PNIPAM with differing contents of anionic and cationic groups was studied by viscometry andstatic and dynamic light scattering. The level of aggregation of such complexes increases with increasingmixing ratio, while the polymer concentration has only a marginal effect. The complexes were highlyswollen at 25 °C and collapsed in a temperature range up to 50 °C, where the swelling−deswelling processis completely reversible. Even complexes between copolymers of higher contents of ionic groups (up toabout 30%) and complexes between copolymers and pure polyelectrolytes showed a pronounced temperaturedependence of the structural density.
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