Polystyrenesodiumsulfonate

Polyethyleneimine (PEI, ${\overline{M}}_{\mathrm{n}}$ ≈ 60 kDa determined by GPC ${\overline{M}}_{\mathrm{w}}$ ≈ 750 kDa determined by LS) and Polystyrenesodiumsulfonate (PSS, ${\overline{M}}_{\mathrm{w}}$ = 70 kDa), were purchased from Sigma-Aldrich (Steinheim, Germany) and were used without further purification. Fully deuterated PSS (dPSS ${\overline{M}}_{\mathrm{w}}$ = 78.3 kDa Đ< 1.2 by GPC) was purchased from Polymer Standard Service GmbH (Mainz, Germany). Poly(diallyldimethylammoniumchloride) (PDADMAC, ${\overline{M}}_{\mathrm{w}}$ = 135 kDa Đ= 1.8 determined by GPC and ${}^1$ H NMR) was synthesized by free radical polymerization of diallyl-dimethyl-ammonium chloride in aqueous solution, as described in a previous work [23 (link)]. The silicon wafers were a gift from Wacker Chemie AG (München , Germany). The silicon blocks were purchased by Silizium Bearbeitung A. Holm (Tann, Germany).