Double‐network hydrogel with high mechanical strength prepared from two biocompatible polymers

Abstract

Novel double-network (DN) hydrogels with high mechanical strength have been fabricated with two biocompatible polymers, poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG), through a simple freezing and thawing method. Some properties of the obtained hydrogels, such as the mechanical strength, rheological and thermodynamic behavior, drug release, and morphology, have been characterized. The results reveal that in sharp contrast to most common hydrogels made with simple natural or synthetic polymers, PVA/PEG hydrogels can sustain a compressive pressure as high as several megapascals, highlighting their potential application as biomedical materials. In addition, a model for describing the structural formation of PVA/PEG DN hydrogels is proposed: the condensed PVA-rich phase forms microcrystals first, which bridge with one another to form a rigid and inhomogeneous net backbone to support the shape of the hydrogel, and then the dilute PEG-rich phase partially crystallizes among the cavities or voids of the backbone; meanwhile, there are entanglements of molecular chains between the two polymers. Moreover, a mechanism is also proposed to explain the high mechanical strength of PVA/ PEG DN hydrogels. It is suggested that the free motion of PEG clusters in the cavities of PVA networks can prevent the crack from growing to a macroscopic level because the linear PEG chains in the cavities effectively absorb the crack energy and relax the local stress either by viscous dissipation or by large deformation of the PEG chains.

The removal of heavy metal ions from aqueous solutions by novel pH-sensitive hydrogels

“…1 H NMR spectrum of MIM: ı = 3.6 ppm: CH 2 CH 2 O groups in PEG, ı = 4.5 ppm: s, CH 2 groups in vinylbenzyl groups, ı = 5.2 and 5.7 ppm: m, CH 2 CH-groups in vinylbenzyl groups, ı = 6.7 ppm: CH 2 CH-groups in vinylbenzyl groups, ı = 7.3 ppm: phenyl groups in vinylbenzyl groups.…”

“…1 H NMR spectrum (in CDCl 3 ) was recorded on Bruker 250 MHz AC Aspect spectrometer using tetramethylsilane as internal Standard.…”

“…In general, a hydrogel is crosslinked, hydrophilic polymer network arranged in a three-dimensional network with a great capacity for water and it can remain insoluble due to the presence of chemical or physical crosslinks [1,2]. Stimuli-responsive hydrogels have earned the reputation of "smart materials" due to their unique ability to change volume or shape in response to environmental signals.…”

Multi-scale multi-mechanism design of tough hydrogels: building dissipation into stretchy networks

“…72, 91 As the hydrogel is deformed, the short chains can be ruptured to dissipate mechanical energy. Previous studies have shown that the chain-fracture mechanism can be implemented with a wide variety of highly crosslinked polymers, such as poly(2-acrylamido-2-methylpropanesulfonic acid) 20 , glycidyl methacrylated hyaluronan 92 , poly(acrylic acid) 93 , agarose 94 , poly(vinyl alcohol) 95 , gellan gum methacrylate 42 , methacrylated chondroitin sulfate 96 . For example, Fig.…”

Biodegradable Elastic Hydrogels for Tissue Expander Application

“…The crystalline regions of PVA essentially serve as physical crosslinks to redistribute external stresses [31] .…”