İ. Anaç; "Swelling Behavior of Thin...", Jan.7, 13:40, G032
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  • İ. Anaç; "Swelling Behavior of Thin...", Jan.7, 13:40, G032

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Faculty of Engineering and Natural Sciences

 

FENS MAT SEMINARS

 

 

 

 

SWELLING BEHAVIOR OF THIN POLY(N-ISOPROPYLACRYLAMIDE)

 

COPOLYMER GEL LAYERS

 

 

Dr. İlke Anaç,

 

Max Planck Institute for Polymer Research, Mainz, Germany

 

 

 

Abstract

 

A terpolymer of N-isopropylacrylamide (NIPAAm), methacrylic acid (MAA) and 4-methacryloyloxybenzophenone (MaBP) was synthesized by free radical polymerization. NIPAAm provides the responsive behavior, whereas MAA as an ionic component increases the hydrophilicity and prevents the skin effect. The third comonomer MaBP serves as photo-crosslinkable unit. Covalent adhesion of the thin polymer film on the gold-coated substrates was achieved with a photoreactive thiol derivative analogous to MABP. The swelling behavior of poly(N-isopropylacrylamide) (PNIPAAm) gel layers in ethanol, water, and ethanol-water mixtures was characterized by combination of surface plasmon resonance (SPR) and optical waveguide spectroscopy (OWS). A reversed Wentzel-Kramers-Brillouin (WKB) approximation was used to analyze the refractive index gradient of the gel films swollen in ethanol and water. Both ethanol and water are good solvents for PNIPAAm and when they mixed they become a cononsolvent pair for PNIPAAm. The transition temperature of PNIPAAm layers in the mixture of ethanol and water was studied. The transition temperature of the gel films was shifted by changing the solvent composition. A drastic change in the transition temperature from 32.8 °C to 29.7 °C was already observed when the solvent was changed from water to water-ethanol (v/v) mixture which contains only 0.25% ethanol. The effect of NaCl salt (in the range of 10-7 and 1 M) and SiO2 nanoparticles on the swelling ratio of PNIPAAm thin layers was also characterized by the SPR/ OWS. The effect of SiO2 nanoparticles on the transition temperature was investigated but no significant shift in transition temperature was observed.

 

 

7 January 2009, FENS G032 at 13.40