Polymeric hydrogels are soft materials with a three-dimensional (3D) hydrophilic network capable of retaining and absorbing large amounts of water or biological fluids. Due to their customizable properties, these materials are extensively studied for developing matrices for 3D cell culture scaffolds, drug delivery systems, and tissue engineering. However, conventional hydrogels still exhibit many drawbacks; thus, significant efforts have been directed towards developing dynamic hydrogels that draw inspiration from organisms’ natural self-repair abilities after injury. The self-healing properties of these hydrogels are closely associated with their ability to form, break, and heal dynamic bonds in response to various stimuli. The primary objective of this review is to provide a comprehensive overview of dynamic hydrogels by examining the types of chemical bonds associated with them and the biopolymers utilized, and to elucidate the chemical nature of dynamic bonds that enable the modulation of hydrogels’ properties. While dynamic bonds ensure the self-healing behavior of hydrogels, they do not inherently confer adhesive properties. Therefore, we also highlight emerging approaches that enable dynamic hydrogels to acquire adhesive properties.

Multi‐walled carbon nanotubes (MWCNTs) were studied as reinforcing filler in a natural rubber based formulation as partial replacement of carbon black. Four levels of MWCNTs were tested at 2.5, 5, 10 and 15 phr in a compound already containing 50 phr of N375 carbon black. The data obtained were compared with the results of reference compounds filled exclusively with N375 carbon black at equal total filler loading as the nanocomposites. The effects of the addition of MWCNTs are dramatic and cause a strong increase in the green Mooney viscosity and in the cured hardness and moduli with a neat reduction of the elongation at break due to the stiffening effect of the MWCNTs. At 10 and 15 phr level of MWCNTs the 50% modulus results more than doubled in comparison to the reference compound. It is shown that the reinforcing effect imparted by MWCNTs to the natural rubber‐based nanocomposite is almost exclusively due to the hydrodynamic effect exerted by the large anisotropic factor of the MWCNTs molecular threads. Using the Enstein‐Guth equation, it has been shown that if the anisotropy factor (or shape factor) of a reinforcing carbon black is ∼6, in the case of MWCNTs used in the present work such factor reaches the value of 52.5, one order of magnitude higher. Drawbacks of the natural rubber nanocomposites prepared with MWCNTs appear under dynamic testing. The cyclic deformation of the nanocomposite specimens, both under compression or under extension, reveals a strong hysteresis and heat generation due to internal friction between the surface of the nanotubes and the rubber matrix. This fact confirms the poor surface interaction between MWCNTs and the natural rubber matrix.