Preparation Of Polymer Hybrid Materials By ATRP Surface Modification And Its Application In Self-healing Hydrogels

Hydrogels are soft materials containing a large amount of water in a 3D network structure.Due to its bionic properties and excellent biocompatibility,it has been widely used in biology,chemistry,agriculture and other fields.However,these hydrogels may have some problems such as structural degradation and functional failure during the usage of hydrogels.Inspired by the self-healing behavior of organisms,self-healing hydrogels were designed and developed.Self-healing hydrogels can recover their structure and function after damage,but traditional self-healing hydrogels have problems such as low mechanical strength and poor toughness.Herein,nanocomposites were designed by green modification methods such as "Atom transfer radical polymerization"(ATRP)and "Mussel inspired chemistry".By grafting polymer chains on the surface of nanoparticles,the compatibility between nanoparticles and polymers is improved.It was further implanted into polyacrylic acid(PAA)-based hydrogels,which achieve the organic unification of healing and mechanical properties of self-healing hydrogels.The content of this dissertation is mainly divided into the following three parts:1.Self-healing and tough graphene oxide(GO)-supported hydrogels were prepared via surface initiated-atom transfer radical polymerization(SI-ATRP)and photocatalytic modification.Hydrogels with the properties of self-healing,toughness,stiffness and strength have great potential for usage in smart materials.Herein,self-healing and tough hydrogels were successfully prepared after adding modified GO composites,which grafted the functional polymers from the surface of GO.GO@polyacrylonitrile(GO@PAN)was synthesized via SI-ATRP using GO@BiBB as the ATRP initiator.The nitrile groups on GO@PAN were converted to pyridine,for which 2,4,6-triphenylpyrylium tetrafluoroborate(TPPT)was used as the photocatalyst.The prepared GO composites were added into PAA hydrogels formed by in situ radical polymerization.These tough hydrogels have excellent mechanical properties(tensile strength is about 6.1 MPa)and stretchability(elongation at break of about 600%)and a healing efficiency of 90% at ambient temperature.2.Surface engineering of porous carbon for self-healing nanocomposite hydrogels were obtained by mussel inspired chemistry and metal-free photoinduced electron transfer ATRP(PET-ATRP).In this work,surface-functionalized microcapsules from porous carbon nanospheres(PCNs)were successfully prepared by mussel inspired chemistry and PET-ATRP.These functional microcapsules are introduced into self-healing hydrogels to enhance their mechanical strength.The PCNs synthesized by a simple soft template method are mixed with linseed oil for loading of the biomass healing agent,and the microcapsules are first prepared by coating polydopamine(PDA).PDA coating is used to fix ATRP initiator to initiate the polymerization of 4-Vinylpyridine(4VP)on the surface of microcapsules through PET-ATRP.Using these functional microcapsules,the self-healing efficiency of hydrogels was about 92.5% after 4 h at ambient temperature and the healed tensile strength can be held at 2.5 MPa with a fracture strain of 625.2%.All results indicated that the surface-functionalized microcapsules for self-healing hydrogels have remarkable biocompatibility and mechanical properties.3.Tough and dual self-healing nanocomposite hydrogels were designed and synthesised for the usage at cold environments.Recently,hydrogels with freezing resistant and healing performance at cold environment have garnered considerable attention in the scientific community.In this paper,microcapsules with dual self-healing function are obtained by PCNs loading low-temperature healing agent eicosapentaenoic acid(EPA)and surface functionalization.Then,a simple and effective one-pot method was used to obtain a double self-healing nanocomposite hydrogels with low temperature resistance under the in situ copolymerization of acrylate-guar(AGG)and acrylic acid(AA)monomer.Even under-20 °C environment,these self-healing hydrogels still have 70.2% healing efficiency and maintain a certain mechanical toughness behavior.The excellent performance comes from the synergy between the low temperature healing agent and dynamic boronate ester bonds.At the same time,the introduction of modified guar gum increases the hydrogel's resistance to ice crystals.This work offers a new solution to fabricate hydrogels with anti-freezing and healing performance in cold environment,which can broaden the working temperature range of hydrogels materials.