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Mredha, Md. Tariful Islam,Pathak, Suraj Kumar,Tran, Van Tron,Cui, Jiaxi,Jeon, Insu Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.362 No.-
<P><B>Abstract</B></P> <P>The mechanical properties (e.g., modulus and strength) of conventional tough hydrogels are considerably inferior to those required for practical load-bearing applications. However, developing hydrogels with a combination of superior mechanical properties such as stiffness, strength, and toughness is very challenging. Herein, we propose a new design strategy based on the synergistic effect of hydrophobic/hydrophilic components to fabricate novel hydrogels with superior mechanical properties. Both hydrophobic and hydrophilic monomers were integrated into copolymer hydrogels using a simple two-step fabrication process, which led to the formation of a randomly distributed interconnected 3D structure of hard-phase and soft-phase regions comprising hydrophobic-rich and hydrophilic-rich components, respectively. The 3D structure of hard-phase regions imparted exceptional stiffness and strength, whereas soft-phase regions provided sacrificial bonds to achieve stretchability and toughness. Different hydrophobic monomers with widely variable extents of hydrophobicity were used. The obtained results indicated that hydrogels based on benzene-containing hydrophobic monomers and exhibiting a higher-than-ambient glass transition temperature can show superior mechanical properties. Highly water-stable physical hydrogels with water contents of 50–60 wt% and exceptionally high Young’s modulus (150–280 MPa), tensile strength (7–17 MPa), and fracture energy (6680–7450 J/m<SUP>2</SUP>) were developed; these values are far superior to those of single-component hydrogels and tough hydrogels reported to date. This combination of superior properties, reported here for the first time, is expected to significantly broaden the application of hydrogels. The proposed strategy is quite general and offers further opportunities to develop diverse ultra-stiff, strong, and tough functional hydrogels using suitable monomer combinations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> New strategy of producing hydrogels with superior mechanical properties is described. </LI> <LI> Hydrophobic/hydrophilic components create nanostructure for synergistic property. </LI> <LI> Hydrophobic–rich component imparts stiffness and strength. </LI> <LI> Hydrophilic–rich component imparts stretchability and toughness. </LI> <LI> The prepared hydrogels are very stable in pure water, seawater, and salt solutions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A diffusion-driven fabrication technique for anisotropic tubular hydrogels
Mredha, Md. Tariful Islam,Tran, Van Tron,Jeong, Sin-Gu,Seon, Jong-Keun,Jeon, Insu The Royal Society of Chemistry 2018 Soft matter Vol.14 No.37
<P>A bio-inspired, simple, and versatile diffusion-driven method to fabricate complex tubular hydrogels is reported. The controlled diffusion of small ions from a pre-designed core hydrogel through a biopolymer reservoir solution causes the self-gelation of biopolymers with an anisotropic ordered structure on the surface of the core hydrogel. By controlling the concentration, diffusion time, and flow direction of the ions, as well as the size and shape of the core, various types of complex tubular-shaped hydrogels with well-defined 3D architectures were fabricated. The mechanical properties of the designed alginate-based tubular hydrogels were highly tunable and comparable to those of native blood vessels. The method was applied to form a living-cell encapsulated tubular hydrogel, which further strengthens its potential for biomedical applications. The method is suitable for biopolymer-based reaction-diffusion systems and available for further research on the fabrication of functional biomaterials with various biopolymers.</P>
Multifunctional biomimetic gels with applicability in wide temperature range
Md. Tariful Islam Mredha,Van Tron Tran,Insu Jeon 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Multifunctional soft materials with biomimetic multi-anisotropic functions together with their applicability in harsh environments (heating/freezing) have great potential for the rapidly growing field of soft bioelectronics. However, conventional soft materials such as, hydrogels and elastomers suffer the combination of such extraordinary properties, and in particular the instability of such materials in harsh environments limit their applications greatly. In this study, we have developed a novel class of multifunctional gels by wisely integrating high-strength cellulose with a highly conductive polymer, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), in an extremely low-volatile, high-boiling and low-freezing bio-friendly organic solvent instead of commonly used water/organic solvents. The resulting gel simultaneously exhibits multiple anisotropic functions (e.g., mechanical, electrical, and thermal) with extremely high mechanical properties along with high electrical and thermal conductivity, and stability at wide range of temperatures. Therefore, the gels are expected to have a great potential for numerous applications in next-generation flexible devices.