Berlin 2015 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 22: Interfaces and Thin Films III (joint session with CPP)

DS 22.9: Vortrag

Mittwoch, 18. März 2015, 11:45–12:00, C 243

Effect of Binary Polymer Mixtures on the Growth of Polyelectrolyte Multilayers — •Malte Paßvogel, Peter Nestler, and Christiane A. Helm — Physik, Uni Greifswald, 17487 Greifswald, Germany

The buildup of polyelectrolyte multilayers (PEMs) is investigated in solution with multiple angle null-ellipsometry. Polyanion poly(styrenesulfonate) (PSS) and polycation polydiallyldimethylammonium (PDADMAC) are adsorbed sequentially from 0.1 NaCl solution. After N_trans deposited PDADMAC/PSS layer pairs a transition from parabolic to linear growth occurs, then the thickness per layer pair d_BL is constant. d_BL is 12.3 nm, if the molecular weight (M_w) exceed threshold values which are specific for each polymer (25 kDa for PSS and 80 kDa for PDADMAC). If either the PDADMAC or the PSS molecular weight is decreased below the threshold values, d_BL either falls (for PDADMAC) or rises (for PSS) suggesting very different growth modes. Binary mixtures of PDADMAC and PSS with M_w below and above the threshold value are used, while M_w of the complementary polyion is kept above the threshold. d_BL depends linearly on the mole fraction of the low-molecular-weight PDADMAC. However, d_BL is only influenced by low-molecular-weight PSS, if its molar fraction exceeds 90%. Always, the same linear relationship between N_trans and d_BL is found. These observations can be explained with an asymmetric growth model of polyelectrolyte multilayers.