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Abstract:
The switching behavior of stimuli-responsive mixed polymer
brushes (d ) 11 nm) was monitored for the first time
in liquid phase in situ by infrared spectroscopic ellipsometry
(IRSE). IRSE is presented as a new, sensitive in situ
tool for online analysis of chemical changes in a thin
complex film at the solid/liquid interface. Responsive
behavior (protonation and deprotonation reaction) of the
poly(acrylic acid)/poly(2-vinylpyridine) (PAA-mix-P2VP)
brush was probed in aqueous solutions with pH ranging
from pH 2 to pH 10. Structural and chemical changes in
a thin polymer brush layer were identified from the
analysis of infrared ellipsometric tan¾ spectra during the
variation of pH. Systematic change in pH confirmed the
reversible switching behavior of the PAA-mix-P2VP brush
between three different states: swollen P2VP and compact
PAA chains at pH 2, a compact P2VP...PAA
complex at pH 6.5, and swollen PAA and compact P2VP
chains at pH 10.
