A fluorescence study on swelling of hydrogels (PAAm) at various cross‐linker contents

Abstract

Disk-shaped acrylamide (AAm) gels were prepared from AAm with various N,N -methylenebisacrylamide (Bis) contents as cross-linker in the presence of ammonium persulfate as an initiator by free-radical cross-linking copolymerization in water. Polyacrylamide (PAAm) gels were dried before using for swelling experiments. Steady-state fluorescence spectrometer was employed during the swelling of PAAm hydrogels in water. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine from various Bis content gel samples was measured during in situ swelling process. It was observed that fluorescence intensity decreased as swelling has proceeded. Gravimetric and volumetric experiments were also performed. The Li-Tanaka equation was used to determine the swelling time constants, τ c , and cooperative diffusion coefficients, D c , from intensity, weight, and volume variations during the swelling processes. It was observed that swelling time constants, τ c , increased and diffusion coefficients, D c , decreased as the cross-linker content was increased. C

Recent progress in hydrogel delivery systems for improving nutraceutical bioavailability

“…The rheology of beads may therefore vary considerably: soft to hard; rubbery to brittle; reversible to irreversible. These rheological attributes are important for certain applications since they influence the stability of the hydrogel beads to shrinking or swelling under appropriate solution or environmental conditions (Aktas, Evingur, & Pekcan, 2009;Koetting, Peters, Steichen, & Peppas, 2015;Voo, Ooi, Islam, Tey, & Chan, 2016) or to disruption in the presence of mechanical forces, such as stirring, flow through a pipe, or mastication (Farres, Moakes, & Norton, 2014;Wu & McClements, 2015).…”

Modeling and Investigation of the Swelling Kinetics of Acrylamide-Sodium Acrylate Hydrogel

“…In the literature Tanaka and Filmore [21] constructed a kinetic model of the absorbent gels swelling. After this study Li and Tanaka [22] added new approaches about the swelling and shrinking of gels which were then implemented by many researchers [23,24].…”

Swelling Kinetics of PAAm–κ-Carrageenan Composites: A Fluorescence Technique

“…The same technique was employed to study swelling of AAm gels with various cross-linker concentrations, where decrease in I tr was explained using the frozen blob model. [19] As far as the correction of fluorescence emission is concerned that a totally empirical formula has been introduced [20,21] to produce the meaningful results for the fluorescence quenching mechanisms. Here, the main idea is to eliminate the structural fluctuation due to the frozen blobs and holes during swelling by using I sc , i.e., one has to produce the corrected fluorescence intensity, I, by dividing the emission intensity, I em , by the scattering intensity, I sc , to exclude the effect of turbidity of the gel on the fluorescence emission intensity and elaborate the Stern-Volmer model by using solely the fluorescence intensity, I.…”

“…We reported the PAAm hydrogel swelling for various temperatures and cross-linker contents by using steady-state fluorescence (SSF) technique. [20,21] The swelling time constants decreased and diffusion coefficients increased as the swelling temperature was increased and, also, the cooperative diffusion coefficient decreased as the cross-linker content was increased. The photon transmission technique was also used to study the swelling properties of κ-carrageenan (κC) gels prepared in various concentrations.…”