Nonlinear viscoelasticity of and structural modulation in guar gum-enhanced triple-network hydrogels

The effect of the presence of guar gum (0–0.75 wt%) in a thermo-responsive triple-network (TN) PVA/TA/PVA-MA-g-PNIPAAm hydrogel (PVA: polyvinyl alcohol; MA: methacrylate, PNIPAAm: poly-N-isopropyl acryl amide; TA: tannic acid) with respect to the structural, mechanical, and viscoelastic properties was mapped. A comprehensive analysis, using large-amplitude oscillatory shear (LAOS), SEM imaging, XRD, and mechanical analysis revealed that guar enhances hydrogel crystallinity (up to 30% at 0.75 wt%), which goes along with a strain hardening. The hydrogel achieved superior mechanical performance at a gum concentration of 0.5 wt% with a 40% increase in shear-thickening, an enhanced strain tolerance in nonlinear regimes, and a good mechanical robustness (maximum elongation to break of 500% and stress of 620 kPa). The hydrogel with 0.5 wt% guar exhibited also a good thermal response (equilibrium swelling ratio changed from 8.4 at 5 °C to 2.5 at 50 °C) and an excellent thermal cycling dimensional stability. Higher guar concentrations reduce structural resilience, leading to brittle hydrogels with lower extensibility and viscoelastic stability.

Subjects

crystallinity | guar gum | large-amplitude oscillatory shear (LAOS)

DDC Class

540: Chemistry

620.1: Engineering Mechanics and Materials Science

Funding(s)

SFB 1615 - SMARTe Reaktoren für die Verfahrenstechnik der Zukunft

SFB 1615 - Teilprojekt A01: Stimuli-responsive Polymere für selbstregulierende Reaktoren: Von grundlegenden Phänomenen zum Reaktordesign

Publication version

publishedVersion

Lizenz

https://creativecommons.org/licenses/by/4.0/

Name

polymers-17-00597.pdf

Type

Main Article

Size

11.79 MB

Format

Adobe PDF

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Nonlinear viscoelasticity of and structural modulation in guar gum-enhanced triple-network hydrogels