Regensburg 2013 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 9: Poster: Interfaces and Thin Films (joint session with DECHEMA and VDI)
CPP 9.27: Poster
Monday, March 11, 2013, 17:30–19:30, Poster C
Influence of polymer molecular weight on the parabolic and linear growth of PDADMAC/PSS multilayers — •Peter Nestler and Christiane A. Helm — Inst. für Physik, Uni Greifswald, D-17487 Greifswald
The buildup of polyelectrolyte multilayers (PEMs) is investigated under in-situ conditions using multiple angle null ellipsometry. Polyanion PSS and polycation PDADMAC are adsorbed from 0.1 M NaCl solution. First the PEMs grow parabolically with the number of deposited layer pairs. This behaviour is attributed solely to the PDADMAC adsorption, while each PSS adsorption step leads to a constant thickness increase. After Ntrans layer pairs a sharp transition from a parabolic to a linear growth occurs. Depending on the molecular weight of the polyelectrolytes, three different regimes of Ntrans are found: For PDADMAC polymer weight above 100 kDa and PSS polymer weight above 30 kDa, the transition occours constantly after 15 adsorbed layer pairs. In the case of lower molecular weights both polyelectrolytes show an opposite influence on Ntrans. A lower PDADMAC polymer weight leads to a decrease (down to 8 layer pairs), and a lower PSS polymer weight to an increase of Ntrans (up to 36 layer pairs), respectively. Interestingly, for each combination of molecular weight the value Ntrans is roughly proportional to the thickness increase per deposited layer pair in the linear growth mode (between 4 nm and 23 nm).