The Fabrication And Characterization Of Hydro/Organo Actuator

There are many plants that can respond to external stimuli in natural environment,such as Venus flytrap,Mimosa,wheat awn and other plants.In the field of artificial muscles,soft robots,and sensors,smart materials that can mimic nature’s ability to change shapes are of interest.In particular,hydrogels can swell or shrink when the external environment(temperature,light,pH,electricity,salt)changes.However,single network hydrogel can not mimic the complex deformation of a plant due to the isotropic nature.The bilayer hydrogel structure actuators attracted increasing attention with their anisotropy structures and can therefore perform more complex actions.But,the bilayer actuators mainly are hydrogels,and can only respond to the water system,which limits their application fields.In addition,the bilayer hydrogel system needs multi-step synthesis,and the interface combination is usually fragile.The reported hydro/organo Janus actuator cannot show different response to different organic solvents and the "organogel" part can only be synthesized by bulk polymerization.Additionally,in all actuators which consist of hydrogels,the hydrogels lose their desirable properties once the temperature decreases below the freezing point of water.All of these severely restrict the manufacturing method and using range of the actuator.To address these shortcomings and broaden the application fields of soft actuators,we have developed hydro/organo Janus copolymer by using two common macromonomers through one-step non-conventional interfacial polymerization.The mechanism and performance of the bilayer structure actuator have been thoroughly studied.The main parts of this thesis can be divided into the following two sections:(1)Aqueous solution system(macromonomer polyethylene glycol monomethyl ether methacrylate 500(PEGMA),macromolecular crosslinking agent polyethylene glycol diacrylate 700(PEGDA)and photocrosslinking agent)and organic solution system(macropolypropylene glycol monobutyl ether acrylate 2500(PPGMA),macromolecular crosslinker polypropylene glycol diacrylate 2000(PPGDA)and photocrosslinker)polymerized together with phase separation to obtain a hydro/organo bilayer structure under UV light conditions.The Janus copolymer show twice response ability in many organic solvents because of the presence of the dilayer active layer.By studying the respective swelling ratio of the pure hydrogel network and organogel network,we found that the Janus actuator has polarity-response behavior,with a polarity of 4.3 as the cut-off point.When polarity lower than 4.3,the actuator bend toward the hydrogel network,when polarity higher than 4.3,it bends towards the organogel network.The copolymer can achieve directional bending,site-specific bending and twice response bending.A smart sensor that detects solvent leakage and four-armed gripper are designed to demonstrate potential applications for polarity detecting and twice response device are also developed and provide new ideas for future applications.(2)Aqueous solution system(acrylic acid(AA),macromonomer polyethylene glycol monomethyl ether methacrylate 500(PEGMA),macromolecular crosslinking agent polyethylene glycol diacrylate 700(PEGDA)and photocrosslinking agent)and organic solution system(macropolypropylene glycol monobutyl ether acrylate 2500(PPGMA),macromolecular crosslinker polypropylene glycol diacrylate 2000(PPGDA)and photocrosslinker)are mixed together and synthesis in one-step polymerization to obtain hydrogel/organogel Janus bilayer structure under UV light conditions.By studying the swelling ratio of the pure hydrogel network and organogel network,respectively,we found that the structure has multiple response(water,pH,salt,oil)but without polarity response.The copolymer can realize undirectional bending and site-specific bending,and a smart sensor for detecting solvent leakage and a four-armed gripper for grabbing weights are designed to demonstrate its potential application.In addition,this work demonstrates that with PEGMA and PPGMA as the matrix and other responsive hydrophilic monomers or hydrophobic monomers can also perpare Janus copolymers by one-step interfacial copolymerization,which expands the applying range of non-traditional interfacial copolymerized monomers and also expands the varieties of functional copolymer materials.The Janus copolymer providing new ideas for the design of multifunctional materials in the future.