Double-network hydrogel with high mechanical strength prepared from two biocompatible polymers (original) (raw)
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J. Mater. Chem. B, 2015
A novel physically linked double-network (DN) hydrogel based on natural polymer konjac glucomannan (KGM) and synthetic polymer polyacrylamide (PAAm) has been successfully developed. Polyvinyl alcohol (PVA) was used as a macro-crosslinker to prepare the PVA-KGM first network hydrogel by a cycle freezing and thawing method for the first time. Subsequent introduction of a secondary PAAm network resulted in super-tough DN hydrogels. The resulting PVA-KGM/PAAm DN hydrogels exhibited unique ability to be freely shaped, cell adhesion properties and excellent mechanical properties, which do not fracture upon loading up to 65 MPa and a strain above 0.98. The mechanical strength and microstructure of the DN hydrogels were investigated as functions of acrylamide (AAm) content and freezing and thawing times. A unique embedded micro-network structure was observed in the PVA-KGM/PAAm DN gels and accounted for the significant improvement in toughness. The fracture mechanism is discussed based on the yielding behaviour of these physically linked hydrogels. † Electronic supplementary information (ESI) available: The frequency (a) and amplitude (b) dependence of storage modulus G 0 of the PVA-KGM hydrogels; the frequency (a) and amplitude (b) dependence of storage modulus G 0 of the PVA-KGM/PAAm DN hydrogels; the effect of MBAA concentration on the compressive strength of the PVA-KGM/PAAm DN hydrogel. See
2008 J Biomedical Materials Research Part A.pdf
In this study, alginate polymers are used to get homogeneous cylindrical or spherical gels. MRI techniques are employed to study homogeneity of these gels. Four different alginates are used and, for each one, five different concentrations for mechanical tests and three different concentrations for release tests are studied. Mechanical tests are performed to get gels' linear viscoelasticity region and then to evaluate their crosslink density in relation to polymer concentration. Afterwards, three model molecules (theophylline, vitamin B 12 , and myoglobin) are loaded within gels to study the release kinetics in water from both cylindrical and spherical gels. Diffusion coefficients calculated from these experiments are then used to estimate the polymeric network mesh wideness. This work shows how crosslink density increases with polymer concentration regardless of the alginate type considered. In addition, while vitamin B 12 diffusion coefficient is inversely proportional to crosslink density, myoglobin is too large to diffuse through the polymeric network, whatever the alginate type and polymer concentration. At the same time, theophylline is too small to be sensibly affected by increasing the polymeric network crosslink density. Finally, MRI analysis and vitamin B 12 diffusion coefficient values prove that, structurally speaking, cylinders and spheres are similar and homogeneous.
Engineering the Microstructure of Hydrogels to Achieve Enhanced Mechanical Properties
Hydrogels are three-dimensional, cross-linked, polymeric networks that are typically soft materials that contain more than 90% water. Many technologies require hydrogels with improved mechanical properties (modulus, failure properties and toughness). Drawing inspiration from biological systems that are complex and highly ordered, yet constructed efficiently, this dissertation advances understanding of multi-component hydrogels. This work also develops correlating relationships of composition, water content, microstructure network properties and mechanical properties. This dissertation investigates three multi-component hydrogel systems which fall into the category of interpenetrating network (IPN): two or more networks which are interlaced, independent of each other and each network is covalently cross-linked. (1) Semi-IPN hydrogels: A subcategory of IPNs in which two or more networks are interlaced and independent of each other, but one is chemically cross-linked and one is an entangled polymer. A systematic study of the formulations of single-network (SN) and semi-IPNs of agarose and poly(ethylene glycol) diacrylate (PEGDA) showed that these gels typically exhibited an effect somewhat greater than the sum of the two component SNs, in moduli, fracture stress and toughness. The semi-IPNs of agarose/PEGDA also behaved as ideal elastomers. Imaging hydrated semi-IPNs of agarose/PEGDA using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the semi-IPNs had pores sizes that are between the two SNs, 1-4 μm pores. The pore size decreased as the PEGDA concentration was increased. (2) Double-network (DN) hydrogels: A subcategory of IPNs in which two independent, I want first want to acknowledge my committee members Drs. Stevin Gehrke, Cory Berkland, Michael Detamore, Paulette Spencer and Laird Forrest for their intellect, support and suggestions as well as challenging me though out my PhD journey. I also would like to acknowledge many of the professors inside and outside of the chemical engineering department who helped my academic career, particularly, Drs.
Networks combining physical and covalent 9 chemical cross-links can exhibit a large amount of dissipated 10 inelastic energy along with high stretchability during 11 deformation. We present our analysis of the influence of the 12 extent of covalent cross-linking on the inelasticity of hydrogels. 13 Four model networks, which are similar in structure but 14 strongly differ in elasticity, have been studied. The aim was the 15 identification of a key structural factor responsible for 16 observing a hysteresis or an elastic deformation. In the 17 employed molecular dynamics study this factor is derived from 18 the underlying structure of each particular hydrogel network. Several structural characteristics have been investigated like the 19 extent of damage to the network, chains sliding, and the specific properties of load-bearing chains. By means of such a key factor, 20 one can predict the deformation behavior (hysteresis or elasticity) of some material, provided a precise description of its structure 21 exists and it resembles any of the four types of a network. The results can be applied in the design of bio-inspired materials with 22 tailored properties.
A phase diagram of neutral polyampholyte – from solution to tough hydrogel
Journal of Materials Chemistry B, 2013
Our recent study has revealed that neutral polyampholytes form tough physical hydrogels above a critical concentration C m,c by forming ionic bonds of wide strength distribution. In this work, we systematically investigate the behavior of a polyampholyte system, poly(NaSS-co-DMAEA-Q), randomly copolymerized from oppositely charged monomers, sodium p-styrenesulfonate (NaSS) and acryloyloxethyltrimethylammonium chloride (DMAEA-Q) without and with a slight chemical cross-linking. A phase diagram of formulation has been constructed in the space of monomer concentration C m and cross-linker density C MBAA. Three phases are observed for the as-synthesized samples: homogeneous solution at dilute C m , phase separation at semi-dilute C m , and homogenous gel at concentrated C m. Above a critical C m,c , the polyampholyte forms supramolecular hydrogel with high toughness by dialysis of the mobile counter-ions, which substantially stabilizes both the intraand inter chain ionic bonds. Presence of chemical cross-linker (C MBAA >0) brings about a shift of the tough gel phase to lower C m, c. The tough polyampholyte gel, containing ~ 50wt% water, is highly stretchable and tough, exhibits fracture stress of σ b ~ 0.4 MPa, fracture strain of ε b ~ 30, and the work of extension at fracture ~ 4 MJ/m 3. These values are in the level of most tough soft materials. 3 Owing to the reversible ion bonds, the poly(NaSS-co-DMAEA-Q) gels also exhibit complete self-recovery (100%) and high fatigue resistance upon repeated large deformation.
Journal of Polymer Research, 2014
Combining different polymeric systems can be a useful tool to create new networks with different characteristics with respect to the starting materials. In this work, hydrogels composed of gellan gum (GG) and polyethylene glycol dimethacrylate (PEG-DMA) were realized to overcome the fragility problems of physical gels of GG, which limit their biological application as scaffold for tissue engineering. The two polymeric systems were combined using different synthetic approaches, with particular attention to the double network strategy (DN). The influence of several parameters on the mechanical properties, such as the time of diffusion and the molecular weight of PEG-DMA, were evaluated by rheological studies and compressive texture analyses. The hydrogels were also investigated for their ability to swell and release model molecules with different sterical hindrances, such as vitamin B12 and myoglobin. Finally, to estimate the biological safety of the hydrogels, their effect on mitochondrial function of human fibroblasts was investigated.
Research Advances in Mechanical Properties and Applications of Dual Network Hydrogels
International Journal of Molecular Sciences
Hydrogels with a three-dimensional network structure are particularly outstanding in water absorption and water retention because water exists stably in the interior, making the gel appear elastic and solid. Although traditional hydrogels have good water absorption and high water content, they have poor mechanical properties and are not strong enough to be applied in some scenarios today. The proposal of double-network hydrogels has dramatically improved the toughness and mechanical strength of hydrogels that can adapt to different environments. Based on ensuring the properties of hydrogels, they themselves will not be damaged by excessive pressure and tension. This review introduces preparation methods for double-network hydrogels and ways to improve the mechanical properties of three typical gels. In addition to improving the mechanical properties, the biocompatibility and swelling properties of hydrogels enable them to be applied in the fields of biomedicine, intelligent sensors,...
Insight into hydrogels Insight into hydrogels
The development and introduction of injectable biomaterials and the identification of methods through which materials may form in situ are currently the topics of interest in materials science, specifically in the field of biomaterials. Over the last few decades, hydrogels which refers to the swellable polymeric matrices have gained wide attention due to their excellent characteristics such as swelling in different media, pH and temperature sensitivity, and sensitivity to other stimuli. Nowadays, injectable hydrogels have widely been studied due to their excellent insitu gelation at body temperature. These injectable insitu gels serve as depot system which ensures the local and systemic drug and gene delivery. These insitu gels also protect the proteins and peptide drugs invivo from environmental effect. The current review is made to report latest extensive literature regarding hydrogels, their classification, synthesis methods, structure of hydrogel network, methods of crosslinking, environment-sensitive hydrogel system, drug loading, and release, hydrogels as biosensors and applications of hydrogels.