Because of its multiresponsive behavior upon variation of pH value,
temperature, and ionic strength, poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) is an attractive candidate
for adaptive surface coatings, especially in the field of biomedical
sensors. In the presented article, PDMAEMA Guiselin brushes (5–12
nm, dry thickness) were prepared by the grafting-to approach, and
the thermoresponsive UCST-type (upper critical solution temperature)
behavior of the generated films, induced by [Fe(CN)6]3–, was demonstrated for the first time. To clarify
the specific mechanism of the temperature responsiveness, the molecular
interactions between polymer chains and complex ions were studied
by in situ infrared spectroscopy and in situ ellipsometry, showing
wavenumber shifts of the ν(CN) band due to ion pairing
as well as changes of the ν(OH) band intensity due to swelling.
Conclusively, experimental data suggest that the electrostatic interaction
between the two components plays a significant role in the thermoresponsive
behavior of PDMAEMA films. Using this knowledge, the UCST of the PDMAEMA
Guiselin brushes could be adjusted between 34.0 ± 1.2 °C
at pH 8 and 40.7 ± 2.0 °C at pH 5.