Temperature and pH Responsive Hydrogels Using Methacrylated Lignosulfonate Cross-Linker: Synthesis, Characterization, and Properties

Abstract

In this work, biobased hydrogels with temperature and pH responsive properties were prepared by copolymerizing N-isopropyl­acrylamide (NIPAM), itaconic acid (IA), and methacrylated lignosulfonate (MLS), where the multifunctional MLS served as a novel macro-cross-linker. The network structures of the lignosulfonate-NIPAM-IA hydrogels (LNIH) were characterized and confirmed by elemental analysis, Fourier transform infrared, and 13C nuclear magnetic resonance. The equilibrium swelling capacity of the LNIH hydrogel decreased from 31.6 to 19.1 g/g with MLS content increasing from 3.7 to 14.3%, suggesting a strong dependence of water absorption of the gel on MLS content. LNIH hydrogels showed temperature-sensitive behaviors with volume phase transition temperature (VPTT) around the body temperature, which was also influenced by MLS content. Moreover, all LNIH hydrogels exhibited pH sensitivity in the range of pH 3.0 to 9.1. Rheological study indicated that mechanical strength of the gel also increased with MLS content. The results from this study suggest that lignosulfonate derivative MLS is a potential feedstock serving both water-absorbing moiety and cross-linker for preparation of biobased smart hydrogels.

A Novel pH- and Salt-Responsive N-Succinyl-Chitosan Hydrogel via a One-Step Hydrothermal Process

“…Figure 3 shows the interior morphological structures of freeze-dried GNCH with different GPTMS contents. All the hydrogels display a continuous and porous three-dimensional structure, which is caused by phase separation and sublimation of removing water during the freeze-drying process [41]. In addition, the pore size of hydrogel became larger as GPTMS contents increased.…”

Synthesis of Thermo-Responsive Block-Graft Copolymer Based on PCL and PEG Analogs, and Preparation of Hydrogel via Click Chemistry

“…Comparing the gel pore sizes in Figure 8a–d, it was found that the pore size of the first gel was slightly smaller than the second one. This is because the observed porous structure of freeze-dried hydrogels were due to the phase separation of the gels during rapid freezing and subsequent removal of the water by sublimation which left voids in place where the water previously occupied, and the increased cross-link density results in the second gel faster phase separation during freezing [43]. Then, comparing the changes of the two gels between 25 °C with 40 °C, it can be seen that the gel was in a shrinking state at 40 °C, and the pore size of three-dimensional network become smaller.…”

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

“…Increasing the content of lignin in hydrogels significantly improved the mechanical properties of the hydrogels [439] and they show excellent strength properties. The biodegradation of the lignin-based hydrogel depends on the crosslink density and the phenolics content in the hydrogel.…”