Investigation of Drying of Poly(N-isoproplacrylamide-co-acrylamide) by Fluorescence Technique

Abstract

The steady-state fluorescence technique was performed on drying of various molar percentages of poly(N-isopropylacrylamide-co- acrylamide) [poly(NIPA-co-AAc)] to elucidate the mechanism of temperature-induced phase separation and the effect of monomer content. Poly(NIPA-co-AAc) copolymers were prepared by free radical cross-linking copolymerization. The fluorescence intensity I of pyranine introduced as a probe increased as drying time was increased for all samples. The behavior of I was modeled by using the SternVolmer equation combined with the moving boundary diffusion model. The desorption coefficient D increased as NIPA content was increased at a given temperature. Gravimetric and volumetric experiments also supported the results of the fluorescence technique. The energy E values were measured for the drying processes for each molar percentage of NIPA monomer content by using fluorescence gravimetric and volumetric methods respectively. It is understood that E values decrease by increasing NIPA content until 50% NIPA and then increase after 50% NIPA indicating that the phase separation has occurred at 50% NIPA. (c) 2012 Wiley Periodicals Inc. Adv Polym Techn 32: E231E240 2013View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21269