Berlin 2001 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 18: Poster: Polymer Blends, Heterogeneous Systems, Colloids and Nanoparticles, Interfaces, Polyelectrolytes

CPP 18.23: Poster

Mittwoch, 4. April 2001, 12:30–15:00, AT1

1H-NMR-Investigation of the Phase Transition of Thermoreversible Polymers in Solution and at Interfaces — •Anders Larsson^1,2, Dirk Kuckling³, and Monika Schönhoff¹ — ¹Max-Planck Institute of Colloids and Interfaces, D-14424 Potsdam/Golm — ²Institute for Surface Chemistry, P. O. Box 5607, SE- 11486 Stockholm — ³Institute for Macromolecular and Textile Chemistry, TU Dresden, D-010 69 Dresden

The thermoreversible polymer Poly-N-isopropylacrylamide (PNIPAM) shows a coil to globule transition at 32C in solution. The phase transition of PNIPAM and of a charged PNIPAM-copolymer, containing 10% carboxylic groups, are investigated in solution and at the interface by 1H NMR. In solution, the 1H liquids signal is decreasing at the phase transition temperature due to the formation of solid globules. 1H spectra and PFG-NMR diffusion coefficients shows a similar phase transition behaviour for the copolymer as for the homopolymer.

Both polymers are adsorbed to colloidal silica to investigate the phase transition in the restricted geometry of an adsorption layer. A liquid signal arises from tails and loops, and is decreasing with temperature, which is interpreted as a phase transition of the loops and tails. The phase transition is substantially broader than in solution, especially at low surface coverage. For the charged copolymer, the transition is further broadened, and mobile segments remain even above the phase transition. We attribute this to a comparatively mobile arrangement of the copolymer layer at the interface.