Rheological and thermal behaviour of poly(N‐isopropylacrylamide)/alginate smart polymeric networks

Abstract

Interpenetrating polymeric networks based on sodium alginate and poly(N-isopropylacrylamide) (PNIPAAm) covalently crosslinked with N,N -methylenebisacrylamide have been investigated using rheology, thermogravimetry, differential scanning calorimetry, X-ray diffraction measurements and scanning electron microscopy (SEM). An improved elastic response of the samples with a higher PNIPAAm content and increased amount of crosslinking agent was found. The temperature-responsive behaviour of the hydrogel samples was evidenced by viscoelastic measurements performed at various temperatures. It is shown that the properties of these gels can be tuned according to composition, amount of crosslinking agent and temperature changes. X-ray scattering analysis revealed that the hydrophobic groups are locally segregated even in the swollen state whilst cryo-SEM showed the highly heterogeneous nature of the gels.

Thermosensitive Hydrogel for Encapsulation and Controlled Release of Biocontrol Agents to Prevent Peanut Aflatoxin Contamination

“…At high magnification (1000× magnification), the honeycomb structure on the surface of SAP13 and SAPK2 could be noticed. Dumitriu's research revealed a porous morphology with a honeycomblike structure of PNIPAAm/alginate hydrogels crosslinked with N, N'-methylenebisacrylamide (BIS), which is consistent with our results [32]. In contrast, there was no such structure on SA, which was flatter.…”

“…At temperatures above the LCST, the PNIPAAm chains assume a collapsed conformation and separate from the water phase; meanwhile, the loaded substances are also expelled from the gel interior [21]. Temperature-responsive hydrogel microspheres composed of alginate and PNIPAAm can be formed by semi-or full interpenetrating network (IPN) methods [30][31][32]. These polymers have been well developed in the field of smart gel materials.…”

Stiff IPN Hydrogels of Poly(Acrylamide) and Alginate: Influence of the Crosslinking Ion’s Valence on Hydrogel’s Final Properties

“…Equilibrium water content was also estimated for IPN hydrogels made in sequential route ( Figure 5). We could see that the water content decreases with the density of crosslinks as expected [21][22][23]. It is remarkable that the water content of hydrogels with Fe 2+ as crosslinker are 5-7% higher than that of hydrogels with Fe 3+ .…”

Preparation, physicochemical and stability studies of chitosan-PNIPAM based responsive microgels under various pH and temperature conditions

“…The rheological studies of stimuli-responsive polymers in aqueous media, is very helpful to elucidate the phase changes and association behaviour in response to shear rate applied at different pH and temperatures [42,43]. The temperature-dependence of chitosan-PNIPAM hydrogel viscosity, in aqueous media at a constant pH ≈ 6, is shown in Fig.…”