Journal of Colloid and Interface Science, Vol.387, 95-105, 2012
Temperature and pH dual-responsive coatings of oligoperoxide-graft-poly (N-isopropylacrylamide): Wettability, morphology, and protein adsorption
Poly(N-isopropylacrylamide) (PNIPAM) coatings attached to glass with novel approach involving polymerization from oligoperoxide grafted to surface with (3-aminopropyl)triethoxysilane exhibit not only temperature- but also pH-dependence of wettability and protein adsorption. Wettability and composition of coatings, fabricated with different polymerization times, were determined using contact angle measurements and Time Of Flight-Secondary Ion Mass Spectrometry (TOF-SIMS), respectively. Thermal response of wettability, measured between 20 and 40 degrees C, was prominent at pH 9 and 7 and diminished or absent at pH 5 and 3. This indicates a transition between hydrated loose coils and hydrophobic collapsed chains that is blocked at low pH. Higher surface roughness and dramatically increased adsorption of model protein (lentil lectin labeled with fluorescein isothiocyanate) were observed with AFM and fluorescence microscopy to occur in hydrophobic phases (at pH 3, for pH varied at constant temperature of 22 degrees C and at similar to 33 degrees C, for temperature varied at constant pH 9). Protein adsorption response to pH was confirmed by TOF-SIMS and Principal Component Analysis. (C) 2012 Elsevier Inc. All rights reserved.
Keywords:Stimuli-responsive polymer coatings;Graft polymerization;Wettability;Protein adsorption;Time Of Flight-Secondary Ion Mass Spectrometry