Fatigue‐Resistant, Notch‐Insensitive Zwitterionic Polymer Hydrogels with High Self‐Healing Ability

Abstract

Introducing self-healing properties into hydrogels can prolong their application lifetime. However, achieving mechanical strength without sacrificing self-healing properties is still a major challenge. We prepared a series of zwitterionic polymer hydrogels by random copolymerization of zwitterionic ionic monomer (SBMA), cationic monomer (DAC) and hydrophilic monomer (HEMA). The ionic bonds and hydrogen bonds formed in the hydrogels can efficiently dissipate energy and rebuild the network. The resulting hydrogels show high mechanical strength (289-396 KPa of fracture stress, 433-864 % of fracture stress) and have great fatigue resistance. The hydrogel with a 1 : 1 molar ratio of SBMA:DAC possesses the best self-healing properties (self-healing efficiency up to 96.5 % at room temperature for 10 h). The self-healing process is completely spontaneous and does not require external factors to assist. In addition, the hydrogel also possesses notch insensitivity with a fracture energy of 12000 J m À 2. After combining the conductivity of RGO aerogel, the hydrogel/RGO composites show good strain sensitivity with high reliability and self-healing ability, which has certain significance in broadening the application of these zwitterionic hydrogels.

Ultra‐stretchable, self‐healable, and reprocessable ionic conductive hydrogels enabled by dual dynamic networks

“…When the samples are stretched, the notch does not expand immediately. Although the stress continues to act on the incision, these dynamic expanded networks effectively dissipate energy, thus reducing the stress concentration at the notch 26 . Furthermore, the fracture strain and fracture energy of DICH‐2 were calculated by stress–strain curves (Figure 4C,D).…”

Recent Advances in Zwitterionic Hydrogels: Preparation, Property, and Biomedical Application

“…On the premise of keeping enough antifouling properties, other functional groups which can be used to stabilize polymer networks are also gradually introduced to enhance zwitterionic hydrogels. There are two main categories: (1) introducing hydrophobic groups/intermolecular hydrogen-bond formation moieties into zwitterionic side-chain ( Figure 5 c) [ 54 , 55 , 56 , 57 ]; (2) copolymerization of zwitterionic monomers with different functional monomers ( Figure 5 d) [ 44 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ]. At present, through the selection of different monomers, zwitterionic hydrogels have been able to achieve various aspects of strength and elasticity regulation to promote their application.…”

“…( d ) Copolymerization of SBMA, cationic monomer (DAC), and HEMA with reversible ionic bonds and hydrogen bonds to strengthen hydrogel. Reproduced with permission from [ 60 ]. Copyright 2020 Wiley-VCH GmbH.…”

“…The interfacial interaction between the hydrogel and other materials can be divided into two aspects: adhesion and lubrication. For zwitterionic hydrogels, the dipolar polymer side-chains can interact with other dipolar functional groups [ 72 ] and ionic functional groups [ 60 , 73 ] that may exist on the interface, thus showing adhesion properties. Zwitterions containing quaternary ammonium functional groups and sulfonic functional groups have strong dipole moments, which can form dipole–dipole interactions with polar functional groups such as carboxyl and amino groups in the skin and tissues and achieve the adhesion between hydrogels and tissues ( Figure 7 a) [ 63 , 74 ].…”

Recent Advances in Mechanical Reinforcement of Zwitterionic Hydrogels

“…The integration of zwitterionic pSBAA and conductive PEDOT: PSS promoted charge transfer through the optimized conductive path and further acted as a fully polymeric biosensor. Yang et al [ 101 ] also introduced 2-Hydroxyethyl methacrylate (HEMA) with hydrogen bonding ability and 2-(dimethylamino) ethylacrylatemethochloride (DAC) with electrostatic bonding ability to copolymerize with zwitterion SB 3 MA 2 . When the molar ratio of the three components was HEMA:DAC:SBMA = 2:4:4, the copolymer hydrogel exhibited tensile strain of 6.8 mm/mm, tensile stress of 330 KPa, and optimum self-healing efficiency (96.5% at room temperature for 10 h).…”