Study On Preparation And Properties Of Acrylamide-Acrylamidophenylboronic Acid-based Hydrogels

The research theme is focusing on the preparation of tough and strong hydrogels with facile method.The structures,properties and applications of resulting hydrogels are related by mechanical property tests,swelling behavior tests and structure characterization.Chapter 1,2?4,and 5 are review,experimental section and conclusion,respectively.(1).A novel hydrogels with good mechanical properties(acrylamide-acrylamino phenylboronic hydrogels,AP hydrogels)is developed by facile free radical copolymerization of acrylamide and phenylboronic monomer.22 sets of hydrogel samples are prepared to study on the effect of compositions(content of 3-acrylamidophenylboronic acid,acrylamide and N,N'-methylenediacrylamide)on mechanical properties,study on the effect of compositions and environmental conditions on swelling behaviors and explore the structures of AP hydrogels.The resulting hydrogels without any cross-linker show high stretchability(break elongation>2000%),high resilience(>75%)and anti-fatigue properties.It is found that the tensile work is maintained more than 78%after 10 times of loading-unloading recycles.In addition,the mechanical properties of hydrogels can be adjusted and optimized by adding proper amount of covalent cross-linker and changing the amount of main monomer,acrylamide.The hydrogels can be highly swollen in water,showing unique swell behaviors and responsive properties to pH and glucose.It is further revealed that other phenylboronic monomers and acrylamide can be utilized to fabricate hydrogels with good mechanical properties using the same methods,which shows the universality of this method.It is assumed that the hydrogels are cross-linked by hydrogen bondings between different groups,which is confirmed by structure characterization and calculation.(2).Cellulose nanofibers,with high strength and modulus,are selected to modify AP hydrogels,which is inspired by fiber reinforced composites.14 sets of hydorgels are prepared to study on the effect of types and content of cellulose nanofibers,and cross-linker content on the mechanical properties of modified AP hydrogels.The modulus,strength,toughness and compressive properties are highly improved while the facile processability,high stretchability and unique swelling behaviors are maintained.After adding 0.5 wt%of cellulose nanofibers,the modulus,strength and tensile work are improved by 428%,112%and 108%,respectively,while the fracture energy is as large as 2211 J/m2 and hydrogels present self-recovery property.It is assumed that the interactions between stiff cellulose nanofibers and polymer networks result in the stress transfer,improvement of stiffness and the property of resistance to crack propagation.(3).During the preparation process of cellulose nanofibers modified AP hydrogels,the anionic polymer of sodium polyacrylate,graphene oxide or macromolecular covalent cross-linker of poly(ethylene glycol)dimethacrylate are added.14 sets of hydrogels using above three kinds of additives are prepared.Mechanical properties and thermal properties of resulting hydrogels are tested.It is found that each additive shows improved results.When 9 wt%of sodium polyacrylate with respect to cellulose nanofibers are added,the elongation,fracture stress and tensile work are improved by 45%,12%and 55%.Graphene oxide combined with N,N'-methylenediacrylamide shows reinforced effect as well,while macromolecular cross-linker can maintain the homogeneity of hydrogel networks.The main significance of this thesis is that a facile method is developed to prepare tough and strong hydrogels with potential applications in drug delivery and release,and smart materials(such as microvalves).