Preparation Process Of Anisotropic Hydrogel Fibers Based On In-situ Polymerization Of N-isopropylacrylamide

In recent years,compared to rigid robots,soft robots have gradually become a hot spot in the field of intelligent robot research due to their good flexibility,and intelligent hydrogels are one of the ideal materials for soft robot manufacturing.Among them,poly-N-isopropylacrylamide(PNIPAM),which has temperature-sensitive properties,has attracted more and more interest and attention of scientific researchers due to its side chain containing both hydrophilic and hydrophobic groups.Fibrillating the hydrogel makes it have the advantages of high porosity and large specific surface area while retaining its own characteristics,which is more conducive to the production of structural support for efficient soft robot materials.At present,most polymer fibers are prepared by electrospinning.This method requires simple equipment and has good process controllability.It is a spinning process that can continuously produce nanofibers.This thesis takes N-isopropyl acrylamide(NIPAM)as the research object.Under the premise of blending with polyethylene oxide(PEO),NIPAM monomer nanofibers are prepared by electrospinning equipment.By adjusting parameters and treating NIPAM fiber with in-situ polymerization and cross-linking reaction,finally we obtained anisotropic PNIPAM fiber,the main research contents and results include the following aspects:(1)using NIAPM,2,2`-dicyano-2,2`-azopropane(AIBN)and N,N`-methylene bis(acrylamide)(BIS)as the raw materials,1:1 volume ratio ofdeionized water and ethanol as binary solvent,PEO as additive,by adjusting the concentration of PEO and the process parameters of electrospinning,NIPAM monomer fibers with good morphology were successfully prepared.The research results showed that the optimal spinning parameters were:the concentration of PEO was 15%,spinning voltage was 25 k V,and receiving distance was 100 mm.(2)On the basis of the above research,using PEO as a solvent and irradiated NIPAM monomer fibers with ultraviolet rays,under the action of the photoinitiator AIBN and the crosslinking agent BIS,the NIPAM inside the fiberwas in situ polymerized and crosslinked,Thus the PNIPAM hydrogel fiber was generated.After washing,the morphology and physical and chemical properties of the fiber were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),tensile experiment and water drop contact angle measurement.The experimental results showed that thefiberschanged from monomer that are easily soluble in water to temperature-sensitive hydrogel,the average diameter of the fibers was reduced,and the mechanical property of the fibers was improved.(3)Utilizing the influence of drum rotation speed on fiber orientation,a highly anisotropic PNIPAM hydrogel fiber was successfully prepared,and its temperaturesensitive characteristics and mechanical properties were investigated.The results showed that high rotation speed can significantly improved the orientation of the fiber,and the temperature sensitivity and tensile resistance of the highly anisotropic PNIPAM hydrogel fiber were obviously different in the parallel and vertical directions of the fiber arrangement.