Recent advances in dynamic covalent bond-based shape memory polymers

Abstract

Dynamic covalent bond-based shape memory polymers (DCB-SMPs) are one of most important SMPs which have a wide potential application prospect. Different from common strong covalent bonds, DCBs own relatively weak bonding energy, similarly to the supramolecular interactions of noncovalent bonds, and can dynamically combine and dissociate these bonds. DCB-SMP solids, which can be designed to respond for different stimuli, can provide excellent self-healing, good reprocessability, and high mechanical performance, because DCBs can obtain dynamic cross-linking without sacrificing ultrahigh fixing rates. Furthermore, besides DCB-SMP solids, DCB-SMP hydrogels with responsiveness to various stimuli also have been developed recently, which have special biocompatible soft/wet states. Particularly, DCB-SMPs can be combined with emerging 3D-printing techniques to design various original shapes and subsequently complex shape recovery. This review has summarized recent research studies about SMPs based on various DCBs including DCB-SMP solids, DCB-SMP hydrogels, and the introduction of new 3D-printing techniques using them. Last but not least, the advantages/disadvantages of different DCB-SMPs have been analyzed via polymeric structures and the future development trends in this field have been predicted.

Debonding-on-demand adhesives based on photo-reversible cycloaddition reactions

“…The dependence of the degree of polymer decrosslinking on the duration of UV irradiation was monitored by the solubility testing of SS1 in THF. 42 From the UV-vis and DSC results discussed in the preceding section, UV irradiation at 254 nm for opening the cyclobutane ring of the coumarin motif in the crosslinked part is considered to result in the decrosslinking of the monomers and oligomers. Because these low molecular-weight oligomers are soluble, the mass loss of the samples by dissolution in the solvent was monitored every 1 h during irradiation.…”

“…[35][36][37][38] Dynamic covalent polymer networks incorporating these light-induced reversible reactions have a wide range of applications, including self-healing polymers [39][40][41][46][47][48][49][50] and shape memory materials. [42][43][44][45] Herein, the cycloaddition reaction of coumarin and its derivatives is one of the most promising reactions applicable to DoD adhesives. It is expected to provide a light-responsive reversible change in adhesiveness and exhibit stability under sunlight owing to its properties, such as irradiation with ultraviolet (UV) light with a wavelength of 365 nm or longer, inducing the cyclodimerization of coumarin, leading to the formation of a dimer with a cyclobutane ring, whereas the reverse photocleavage reaction occurs by irradiation with light at wavelengths below 254 nm, recovering the original monomers.…”

Synthesis and Processing of Dynamic Covalently Crosslinked Polydextran/Carbon Dot Nanocomposite Hydrogels with Tailorable Microstructures and Properties

“…The amine-functionalized carbon dots (CDs) were prepared through a one-pot method, where 3-aminopropyltriethoxysilane (APTES) served as the surface functional ligand to improve the dispersion of CDs in an aqueous solution. − The physical and chemical properties of CDs were characterized using UV–Vis spectroscopy, fluorescence spectroscopy, DLS, TEM, EDX spectroscopy, and FTIR spectroscopy. The synthesized CDs presented the absorption and emission peaks at 327 and 469 nm, respectively (Figure S1a).…”

“…Nanocomposite hydrogels (NC hydrogels) are crosslinked polymer networks embedded with nanomaterials. − NC hydrogels possess higher mechanical strength , and additional functions (such as fluorescence, − near-infrared responsiveness, − electricity, − antimicrobial property, − thermal conductivity, and magnetic responsiveness − ) compared to hydrogels with a polymeric network alone. Nanoparticles can be used as fillers (not involved in the reactions with polymers) or crosslinking agents in NC hydrogels. − Particularly, given the reversible nature of dynamic covalent bonds, NC hydrogels with a dynamic covalently crosslinked network are emerging materials to present a rapid self-healing manner. , Dynamic covalent bonds presented in the hydrogel networks act as sacrificial bonds for energy dissipation after stress, effectively enhancing the toughness of hydrogels. − In addition, the reversible and stimuli-responsive features of dynamic covalent bonds have been well demonstrated to enable the hydrogels to work as controllable vehicles for molecule delivery. , Furthermore, with the reversible bonding ability, the dynamic covalently crosslinked hydrogels present self-healing and shear-thinning properties, allowing the advanced applications of hydrogels in 3D printing and electrospinning…”

Review of Thermoresponsive Electroactive and Magnetoactive Shape Memory Polymer Nanocomposites

“…In recent years more and more polymers have been produced incorporating dynamic covalent bonds in order to achieve materials that can self-heal, reshape for 3D printing purposes, and have shape memory . There is a wide choice of methods to obtain dynamic covalent bonds, and the corresponding literature − is available.…”