Preparation And Properties Of Hydrogels Tackified By Nucleobases

Hydrogels are a kind of hydrophilic polymer-based soft materials containing a lot of water.On advantage of the outstanding tissue similarity and flexibility,hydrogels have been widely applied in the fields of tissue engineering,drug release,flexible electronics.The structural design of hydrogels can achieve the creation and regulation of various performances,such as mechanical toughness,self-healing behavior,anti-freezing performances,conductivity,and so on.Recently,the development and design of adhesive hydrogels have drawn much attention in flexible electronics.However,some problems of traditional adhesive hydrogels still exist and limit the development and applications of adhesive hydrogel materials.For example,(1)most adhesive hydrogels trend to exhibit a weak mechanical mechanics and adhesion strength;(2)most adhesive hydrogels can not achieve durable adhesive performance and excellent adhesion in wet environments.To address the above problems,this work developed a series of nucleobase-tackified hydrogel materials via the structure design,and successfully endowed the hydrogels with prominent functional behaviors,such as multipurpose adhesion,robust adhesion,repeated adhesion,underwater adhesion,underoil adhesion,and excellent adhesion in a wide temperature range.Furthermore,the hydrogel-based sweaty skin sensors were fabricated based on the wet adhesive and tough hydrogels for monitoring human motion signals.The specific research work is divided into the following sections:(1)A nucleobase-tackified hydrogel strategy was successfully presented and fabricated a series of adhesive hydrogel tackified by independent nucleobase through introducing nucleobase into hydrogels as adhesive factor.Based on the physical adhesion interactions between nucleobase and corresponding elemental components,the adhesive hydrogel tackified by independent nucleobase exhibited an excellent adhesion performance for various solid materials,including polytetrafluoroethylene,plastic,rubber,glass,metal and wood,as well as biological tissues of mice such as spleen,heart,kidney,liver,bone,lung and muscle.Based on the molecular structure of adenine,guanine,thymine,uracil,and cytosine,the specific interfacial adhesion interactions should include metal complexation,hydrogen bonding,hydrophobic interactions,?-? stacking,and so on.Such nucleobase-tackified strategy would provide a new insight for the design and development of adhesive soft materials.(2)In order to further improve the adhesive and tough performances of hydrogels,we fabricated an adhesive hydrogel tackified by nucleobase pairs of adenine and uracil in this part of work.The hydrogen bonding between adenine and uracil can effectively regulate the balance of adhesion and cohesion of the hydrogel system and improve the adhesiveness and toughness of the hydrogels.As expected,the mechanical toughness and adhesive properties were further improved effectively based on the hydrogen bonding between adenine and uracil.Moreover,the adhesive hydrogels tackified by adenine and uracil also exhibited the multipurpose adhesive performance for various solid materials and biological tissues.More importantly,the adhesive hydrogels presented an excellent repeated adhesion behavior based on the prominent balance of adhesion and cohesion.(3)Underwater adhesion plays a significant role in the fields of tissue adhesives,wearable sensors,and bioelectronic interfaces.In above two parts of the work,the polyacrylamide hydrogels tackified by nucleobase presented excellent adhesive performances,but they can not achieve underwater adhesion due to their high hydrophilic character.To address this problem,we first prepared an adenine-driven adhesive organogel through the free radical polymerization.When the organogel is applied for underwater bonding,water molecules will penetrate into the gel system to replace the DMSO molecules,resulting in a solvent exchange phenomenon.The solvent exchange would induce the hydrophobic molecules of gels to aggregate,which significantly improve the hydrophobicity of the gel surface to remove the hydrated layer for underwater bonding.While the adenine groups in the gel network would interact with substrates via the possible physical interactions with enhancing the interfacial adhesion strength.Finally,the organogel was converted into a hydrogel and underwater adhesion interface was constructed.The hydrogel not only demonstrated excellent versatile adhesion to various solid materials in water,but also exhibited high mechanical properties,good recovery properties,and swelling resistance.(4)Based on the above part of the work,a nucleobase-tackified hydrogel with tough adhesion in solvents was successfully fabricated based on the synergistic hydrophilic and hydrophobic composition.On the advantage of the binary synergistic hydrophilic and hydrophobic composition of the hydrogel system,the adhesive hydrogel exhibited a robust adhesion behaviors for various solid materials in water,seawater,acid and alkaline aqueous solutions(p H=3 and p H=10)as well as in various organic solvents such as hexane,chloroform,DMSO,ethanol and bean oil.In addition,the hydrogel not only demonstrated good mechanical toughness,but also achieved good non-swelling properties in diverse aqueous solutions and organic solvents.(5)Self-adhesive hydrogels have attracted great attention in the wearable electronics.However,most adhesive hydrogels cannot achieve a robust adhesion for sweaty skin surface,which limits their applications.To address this problem,in this part of work,a wet adhesive and tough hydrogel was successfully constructed by introducing the nucleobase pairs of adenine and uracil into the hydrogel system of fourth part of work.The hydrogels not only exhibited strong adhesion to various substrates in water and oil,anti-swelling behavior,remarkable mechanical stability,but also achieved stable adhesive and tough performance over a wide temperature range from-20 to 80 °C.Furthermore,a wet adhesive,tough and conductive hydrogel was prepared by introducing conductive ions into the hydrogel system for constructing a hydrogel sweaty skin sensor.Based on its excellent wet adhesion properties,hydrogel sweaty skin sensor can firmly adhere to wet skin of human with monitoring various human movements and physiological activities.It is envisioned that the anti-freezing and tough hydrogel with wet adhesion would draw much interests in the fields of flexible electronic devices,battery adhesives,soft robotics.