Swelling and Orientation Behavior of End-Grafted Polymer Chains by In Situ Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Complementing In Situ Ellipsometry

Mirjam Hofmaier; Patricia Flemming; Olga Guskova; Alexander S Münch; Petra Uhlmann; Martin Müller

doi:10.1021/acs.langmuir.3c01453

Swelling and Orientation Behavior of End-Grafted Polymer Chains by In Situ Attenuated Total Reflection Fourier Transform Infrared Spectroscopy Complementing In Situ Ellipsometry

Langmuir. 2023 Nov 21;39(46):16219-16230. doi: 10.1021/acs.langmuir.3c01453. Epub 2023 Nov 9.

Authors

Mirjam Hofmaier^{1

2}, Patricia Flemming^{1

2}, Olga Guskova³, Alexander S Münch¹, Petra Uhlmann¹, Martin Müller^{1

4}

Affiliations

¹ , Institut Physikalische Chemie und Chemie der Polymere, Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Straße 6, D-01069 Dresden, Germany.
² Chair of Physical Chemistry of Polymeric Materials, Technical University Dresden (TUD), Zellescher Weg 19, D-01069 Dresden, Germany.
³ Institut Theorie der Polymere, Leibniz-Institut für Polymerforschung Dresden e.V., Kaitzer Straße 4, D-01069 Dresden, Germany.
⁴ Chair of Macromolecular Chemistry, Technical University of Dresden (TUD), Mommsenstraße 4, D-01062 Dresden, Germany.

PMID: 37941338
DOI: 10.1021/acs.langmuir.3c01453

Abstract

The literature lacks established concrete parameters for assigning grafted chain regimes. In this context, dichroic in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and in situ ellipsometry were used complementarily, offering new opportunities for conformational analysis of end-grafted polymer chains. Especially polymer chain orientation was studied as a new parameter, among others, for proper chain regime assignment in this report. Alkyne-functionalized poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) with a molecular weight of 49.8 kg/mol and a contour length of around 80 nm was grafted to self-assembled monolayers bearing triazole end groups as reported. Different chain regimes were generated by using three different grafting densities. ATR-FTIR spectroscopy based on the ν(C═O) stretching vibration at around 1728 cm^-1 provided a new direct approach to determine the GD of polymer chains. Significant shifts in the position of the ν(C═O) band comparing dry and wet states were observed, caused by increased hydrogen bonding interactions between PDMAEMA and water. Finally, the averaged orientation of PDMAEMA chains along the z-axis was determined using dichroic ATR-FTIR spectroscopy based on the dichroic ratios of the ν(C═O) band and molecular order parameters S_Z,MOL calculated thereof. High S_Z,MOL values were found for the wet state compared to the dry state, confirming that all GD PDMAEMA samples are in the brush regime in the swollen state.