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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 9: Poster: Interfaces and Thin Films (joint session with DECHEMA and VDI)
CPP 9.26: Poster
Montag, 11. März 2013, 17:30–19:30, Poster C
Interdiffusion within polyelectrolyte multilayers: influence of kind and weight of polycation and the design of diffusion barriers — •Malte Paßvogel1, Peter Nestler1, Ralf Köhler2, and Christiane A. Helm1 — 1Inst. für Physik, Uni Greifswald, D-17487 Greifswald — 2Helmholtz-Zentrum für Materialien und Energien, D-14109 Berlin
With neutron reflectivity the position and width of the internal interface between protonated and deuterated blocks of polyelectrolyte multilayers is determined. First, a standard system formed from PDADMA and PSS (protonated or deuterated) in 0.1M NaCl solution is investigated. Immersion in a concentrated salt solution (1M NaCl) for different annealing times shows interdiffusion. The diffusion constant depends non-linearly on the PDADMA molecular weight. This finding suggests that the diffusing entities are polycation/polyanion complexes. For large PDADMA molecular weight (>150 kDa) no diffusion inside the PEM is found. To explore the influence of the polycations, films made with the branched Polyethylenimine (PEI) and PSS are investigated. These films show a strongly non-linear film growth and very broad internal interfaces. No interdiffusion occurs when these films are immersed in 1 M NaCl. To test the idea that PEI might serve as a diffusion barrier, a PEI layer is placed between a protonated and deuterated PDADMA/PSS block. Immersion of these multilayers in 1M NaCl solution for different times shows that the presence of PEI leads to a broadening of the interface which increases linearly with immersion time suggesting movement of PSS with constant slow speed.