Multivalent Ions as Reactive Crosslinkers for Biopolymers—A Review

Many biopolymers exhibit a strong complexing ability for multivalent ions. Often such ions form ionic bridges between the polymer chains. This leads to the formation of ionic cross linked networks and supermolecular structures, thus promoting the modification of the behavior of solid and gel polymer networks. Sorption of biopolymers on fiber surfaces and interfaces increases substantially in the case of multivalent ions, e.g., calcium being available for ionic crosslinking. Through controlled adsorption and ionic crosslinking surface modification of textile fibers with biopolymers can be achieved, thus altering the characteristics at the interface between fiber and surrounding matrices. A brief introduction on the differences deriving from the biopolymers, as their interaction with other compounds, is given. Functional models are presented and specified by several examples from previous and recent studies. The relevance of ionic crosslinks in biopolymers is discussed by means of selected examples of wider use.

Self-Healing Magnetorheological Elastomer for Vibration Damping

In this work, magnetorheological elastomers (MRE) based on nickel zinc ferrite and natural rubber were prepared. Self-healing capability was employed to the MRE by peroxide induced graft polymerization between zinc thiolate and natural rubber to produce reversible ionic crosslinks that can recover the properties of the fracture materials. Evidence that reversible ionic crosslinks occurred was determined by tensile test of original and healed sample. The results revealed that the tensile strength of the MRE recovered 56% in a minute and almost 100% in 10 minutes at room temperature. The morphology of the fractured surface also showed the fracture area was recovered after the healing processed. The dynamic mechanical analysis of the MREs under cyclic loading were also examined with parallel plate rheometer.

Autonomous self-healing polyisoprene elastomers with high modulus and good toughness based on the synergy of dynamic ionic crosslinks and highly disordered crystals

We designed a novel polyisoprene elastomer with high mechanical properties and autonomous self-healing capability at room temperature facilitated by the coexistence of dynamic ionic crosslinks and crystalline components that slowly reassembled.

Toward strong self-healing polyisoprene elastomers with dynamic ionic crosslinks

We demonstrate the principle in the optimization of the molecular structure for the polyisoprene elastomer with dynamic ionic crosslinks to tune the mechanical and autonomous self-healing properties.

Thermoplastic silicone elastomers based on Gemini ionic crosslinks

Gemini ionic crosslinks produced by neutralization of dicarboxylic and diamino silicones lead in a facile manner to thermoplastic silicone elastomers.

Projection Micro-Stereolithography of Temperature Responsive Mechanically Tough Hydrogels

Temperature responsive hydrogel has attracted considerable attention as an outstanding material for creating a variety of reconfigurable structures. As a well-known temperature responsive hydrogel, poly(N-isopropylacrylamide) (PNIPAAm) has been widely used in various applications. Here, we report high resolution 3D micro fabrication of PNIPAAm structures using projection micro-stereolithography (PμSL). We also show the controllability of degree of swelling and transition temperature of 3D printed PNIPAAm structures by controlling process parameters of PμSL. In addition, we demonstrate improvement of mechanical properties of PNIPAAm by introducing ionic crosslinks into 3D printed PNIPAAm structures to form ionically and covalently crosslinked hybrid networks.