Regensburg 2025 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 41: Charged Soft Matter, Polyelectrolytes and Ionic Liquids I

CPP 41.3: Talk

Friday, March 21, 2025, 10:15–10:30, H38

Orientation analysis in polyelectrolyte multilayer and brush coatings by dichroic ATR-FTIR spectroscopy — •Martin Müller, Mirjam Hofmaier, Patricia Flemming, Olga Guskova, Alexander Münch, and Petra Uhlmann — Leibniz-Institut für Polymerforschung Dresden e.V.

Dichroic ATR-FTIR spectroscopic data on two types of thin oriented polyelectrolyte (PEL) coatings relevant for life science are presented. Trapezoidal silicon multiple internal reflection elements, sealed in-situ cell in ATR mirror attachment with polarizer and commercial FTIR spectrometer were used. (i) At first dichroic ATR-FTIR data on thin PEL multilayer (PEM) coatings composed of a-helical poly(L-lysine) and various polyanions (PLL/PA) at unidirectionally texturized silicon substrates are presented. Based on experimental dichroic ratios RATR, the known angles theta between transition dipole moment (TDM) of Amide I and Amide II vibration and a-helix axis (38°, 73°) and on calculated electrical field components Ex,y,z high in-plane y-axial orientation of PEM was identified. (ii) Secondly, thin cationic PEL brushes with three different grafting densities at silicon substrates were characterized by dichroic ATR-FTIR. Using concept of (i) and angle theta between TDM of n(C=O) vibration of PDMAEMA and molecular main axis (69°), which was determined by atomistic simulations, high out-of-plane z-axial orientation was identified. Swelling in water increased the orientation if compared to dry state. Both PEL coating types may be used as bioactive platforms towards proteins and microorganisms.

Keywords: ATR-FTIR; dichroism; polyelectrolyte multilayer; polyelectrolyte brush; orientation