Stimuli-responsive Polymeric Hydrogels With Multi-functions

As one of the intelligent materials,stimuli-responsive polymeric hydrogels can produce reversible shape deformations or change colors upon external stimuli such as light,electricity,heat,magnetism,chemicals and so on.Due to their promising applications in design and fabrication of biomimetic intelligent devices,smart hydrogels have been paid wide attention.Among them,shape-fixable shape memory hydrogels and morphology changeable hydrogel actuators are two of the most studied smart hydrogels.However,single stimuli-responsive mode and sole function of the corresponding hydrogels limit their further applications.In order to solve the above problems,lots of efforts have been made to realize multi-stimuli-responsiveness and expand multi-functions.The main work can be listed as follows:In the first work,a double network system consisting of chemical crosslinked Polyacrylamide network?PAAm?and physical crosslinked Alginate-Phenylboronic acid-Poly?vinylaclcohol?network?Alg-PBA-PVA?was constructed,by which the hydrogel was endowed with excellent mechanical properties.By integrating the chelation of Alg-Ca²⁺and the dynamic PBA-diol ester bonds,triple shape memory effect has been realized on stretching,macro bending and micro patterns.In addition,the combination of shape memory behavior and self-healing property makes it possible for shape memory after self-healing process as well as self-healing during shape memory procedure.On the basis of previous study,three non-interfering supramolecular interactions,including coil-helix transition of Agar,the coordination of acrylic acid?AAc?and Fe³⁺and the dynamic PBA-diol ester bonds were combined in one hydrogel,which possesses multi-shape memory effect.Due to the controllability of dynamic crosslinking density,the mechanical properties of hydrogel can be tuned by simply treating with Fe³⁺solution or alkali solution.In the next chapter,graphene oxide-poly?N-isopropyl acrylamide??GO-PNIPAM?hydrogel was locally reduced by UV light for NIR-,thermo-responsive 3D complex deformation from two dimension.Furthermore,the introduction of methacrylic acid?MAA?endows the hydrogel with multi-stimuli-responsiveness,for achieving complex deformation from 3D to 3D.Applying ionoprinting method,Fe³⁺was introduced into fluorescent hydrogels,by which the fluorescence of pyrene moieties was quenched and the chelation with carboxylic groups can generate anisotropic structures for shape deformation.On the basis of fluorescence quenching and water-induced actuation,2D and 3D information encryption can be achieved under UV light and being put into water,respectively.What's more,after the replacement of Fe³⁺with H⁺,fluorescence can recover and generated morphologies can be erased.This system may provide a new insights in designing and developing devices for storing hierarchical and multi-dimensional information.Through learning from the design concept of hydrogel actuators,PAAm-PAAc hydrogels with asymmetric structure have been fabricated.Instead of manual deformation,self-actuation paves a novel way for obtaining controllable shape memory hydrogels.In summary,this thesis has done related researches about the multi-functionalization of both shape memory hydrogels and hydrogel actuators.For the former,after having a try on new memorizing method,triple or even multi shape memory effect has been realized through constructing special structures such as double network,single network with multi crosslinks and interpenetrating network,and utilizing two or multi non-interfering dynamic interactions.As for hydrogel actuators,design on anisotropic structure and the introduction of fluorescent property make hydrogels with multi-stimuli-responsive 3D complex deformations,also be one of the candidate materials for information storage.Finally,a self-driven hydrogel with shape memory effect was prepared by integrating the design concept of hydrogel actuators into the shape memory hydrogel systems.