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, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21269