Polyampholyte Hydrogels Reinforced By Multi-scale Strategy And Their Mechanical Behaviors

Hydrogels are a kind of three-dimensional cross-linked polymer network with water as the dispersing medium.The soft and wet properties of hydrogels give their application prospects in the frontier fields of biological tissue engineering,flexible electronics and so on.In fact,there are many natural hydrogels in nature,such as muscles and ligaments and other biological soft tissues;The difference is that most of these natural hydrogels have multi-level structures that can carry and resist external forces at multi-scale levels,giving them soft and tough properties.Inspired by biological soft tissue,this paper hopes to enhance PA gels by using a multi-scale structural design strategy,and systematically study their mechanical behavior.In the second chapter,this paper selects a model PA hydrogel（P（NaSS）-co-DMAEA-Q）and a model for metal ions(i.e.,Fe³⁺).By“the secondary equilibrium method”to introduce Fe³⁺PA water gel,gel in the network by electrostatic interaction between anion and cation to form the ionic bond,at the same time with complexing ability Fe³⁺and anionic groups on polymer chain can be formed metal coordination bond,the collaborative optimization PA hydrogel network structure,realize the ionic bond and coordination bond metal coordination enhancement purposes.In addition,another PA hydrogel(（P（Nass-co-MPTC））system and a variety of polyvalent metal ions(Al³⁺,Zn²⁺,Ca²⁺)were selected to further verify the universality of the proposed enhancement method.Finally,this article also through the Mooney-Rivlin model is discussed by the introduction of metal coordination bond to the influence of the preparation of hydrogels softening and hardening behavior,and further using viscoelastic theory model to discuss the introduction of the metal coordination bond elasticity and stickiness contribution to the hydrogel network,combined with the experimental data and theoretical models to further reveals the enhancement mechanism of those gel.In chapter three,this paper selected PA hydrogel（P（Nass-co-DMAEA-Q））and Fe³⁺as the model.By the method of pre-stretching,the ionic bond and coordination bond were induced to recombine and the molecular chain was fixed in the pre-stretching direction,so that the gel could realize the orientation structure similar to skin collagen fiber.Finally,Mooney-Rivlin was used to analyze the hardening,softening and toughening mechanism of Free-PA-Fe hydrogel.Combined with experimental data and theoretical model,the strengthening mechanism of Free-PA-Fe hydrogel was further revealed,and the semi-flexible model was used to analyze its mechanical response.In chapter four,natural cellulose fibers are introduced into PA hydrogels to prepare composite hydrogels,in which PA hydrogel matrix could form an effective interface with the fibers through effective hydrogen bonds and ionic bonds.The high strength fibers in the composite hydrogels can effectively carry and transfer stress,and the gel network and interface constructed by ionic bonds can effectively dissipate energy,realizing significantly improving its mechanical properties.At the same time,the composite hydrogel also showed a high parallel/vertical adhesion strength ratio（10～25）,which was similar to the adhesion of gecko feet.