Mohammad Vatankhah-Varnoosfaderani

Weak Hydrogen Bonding Enables Hard, Strong, Tough, and Elastic Hydrogels

A new type of rigid and tough hydrogel with excellent elasticity is designed by dense clustering of hydrogen bonds within a loose chemical network. The resultant hydrogel exhibits a good combination of high modulus (28 MPa), toughness (9300 J m(-3) ), extensibility (800%), and tensile stress (2 MPa). Furthermore, the gel displays good fatigue-resistance and complete and extremely fast recovery of shape and mechanical properties (3 min at 37°C).

Solvent-free, supersoft and superelastic bottlebrush melts and networks.

Polymer gels are the only viable class of synthetic materials with a Youngs modulus below 100 kPa conforming to biological applications, yet those gel properties require a solvent fraction. The presence of a solvent can lead to phase separation, evaporation and leakage on deformation, diminishing gel elasticity and eliciting inflammatory responses in any surrounding tissues. Here, we report solvent-free, supersoft and superelastic polymer melts and networks prepared from bottlebrush macromolecules. The brush-like architecture expands the diameter of the polymer chains, diluting their entanglements without markedly increasing stiffness. This adjustable interplay between chain diameter and stiffness makes it possible to tailor the networks elastic modulus and extensibility without the complications associated with a swollen gel. The bottlebrush melts and elastomers exhibit an unprecedented combination of low modulus (∼100u2009Pa), high strain at break (∼1,000%), and extraordinary elasticity, properties that are on par with those of designer gels.

Graphene Oxide/Carbon Nanotube Composite Hydrogels—Versatile Materials for Microbial Fuel Cell Applications

Carbonaceous nanocomposite hydrogels are prepared with an aid of a suspension polymerization method and are used as anodes in microbial fuel cells (MFCs). (Poly N-Isopropylacrylamide) (PNIPAM) hydrogels filled with electrically conductive carbonaceous nanomaterials exhibit significantly higher MFC efficiencies than the unfilled hydrogel. The observed morphological images clearly show the homogeneous dispersion of carbon nanotubes (CNTs) and graphene oxide (GO) in the PNIPAM matrix. The complex formation of CNTs and GO with NIPAM is evidenced from the structural characterizations. The effectual MFC performances are influenced by combining the materials of interest (GO and CNTs) and are attributed to the high surface area, number of active sites, and improved electron-transfer processes. The obtained higher MFC efficiencies associated with an excellent durability of the prepared hydrogels open up new possibilities for MFC anode applications.

Bottlebrush Elastomers: A New Platform for Freestanding Electroactuation

Freestanding, single-component dielectric actuators are designed based on bottlebrush elastomers that enable giant reversible strokes at relatively low electric fields and altogether avoid preactuation mechanical manipulation. This materials design platform allows for independent tuning of actuator rigidity and elasticity over broad ranges without changing chemical composition, which opens new opportunities in soft-matter robotics.

Effect of H2O and reduced graphene oxide on the structure and rheology of self-healing, stimuli responsive catecholic gels

A catechol-containing organogel based on random copolymers of N-isopropylacrylamide (NIPAM) and dopamine methacrylate (NIDO5%) in dimethyl formamide (DMF) was supramolecularly crosslinked by NaBH4 in the presence of reduced graphene oxide (RGO). The focus of the investigations was on the influence of H2O and RGO in the system, which leads to a softening and stiffening, respectively. Whereas RGO tends to restack partially, this tendency was not found in the gels, suggesting a surface coverage of RGO with NIDO5% due to H-bonding and surface crosslinking attributed to the interactions of polar groups of polymer chains with carboxylic and carbonyl groups of RGO sheets proven by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction and spectroscopy (XRD). While RGO leads to the system becoming more brittle, its presence does not lead to an excessive loss of the self-healing characteristics, but it clearly stabilizes the gel when swollen with H2O, as can be seen from the significantly higher modulus and the retained self-healing behavior.

The design of wrinkled microcapsules for enhancement of release rate.

Thermally expandable microcapsules (TEMs) with wrinkled shells are prepared by one-step suspension polymerization, allowing for encapsulation and controlled release of cargos. Wrinkling results from concurrent crosslinking of shell copolymers and vaporization of volatile reagents along with density increase upon polymerization. Through control of the vapor pressure of the reagents and systematic variation of the suspension composition, microcapsules with different degrees of wrinkling are prepared, ranging from locally dimpled to highly crumpled morphologies. The corresponding increase of the surface-to-volume ratio results in increasing release rate of encapsulated oil red dye as a model cargo. As such, in addition to shell thickness and radius, the wrinkleness provides an effective control parameter for adjusting the release rate. The wrinkled microcapsules with a large surface-to-volume ratio may find applications in drug delivery, chemicals scavenging, and self-healing materials.

Self-associations and temperature dependence of aqueous solutions of zwitterionically modified N-isopropylacrylamide copolymers

Thermosensitive copolymer solutions are prepared from various molar ratios of N-isopropylacrylamide (NIPAM) and the zwitterionic monomer N-(methacryloxypropyl)-N,N-dimethyl-N-(3-sulfopropyl) ammonium betaine (Zw) by free radical polymerization. In the current study, we examined the rheological properties of poly (NIPAM/sulfobetaine) copolymer solutions. We found that the rheological properties are conceptually linked with the copolymer chemical structure and chain topology. We also report the effects of bulk molar mass and zwitterions on flow curve ɳ (γ⋅

Mussel‐Inspired Electrospun Smart Magnetic Nanofibers for Hyperthermic Chemotherapy

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