Research On The Properties Of Multi-stimuli Response Shape Memory Polymer Composites

As a kind of smart materials,shape memory polymer?SMP?can sense the changes of the external environment and make corresponding instantaneous responses to the changes.It shows a series of intelligent characteristics,such as self-adaptation,self-regulation and self-healing,which has created a new era of human design and utilization of materials.With the development of science and technology,the application of conventional thermo-induced SMP is limited and in the face of the ever-increasing demands on the using of intelligent materials due to the fact that they can only remember one temporary shape,only exhibit heat-induced shape recovery,and show non-reversible shape memory effect.Therefore,in recent years,SMPs with multi-stimuli response,multi-shape memory effect,two-way shape memory effect,and multifunctionality have been prepared,which add new vitality to the field of smart materials.In this thesis,we did some preliminary explorations in multi-stimuli response and two-way shape memory behavior,light-and heat-actuated two-way shape memory effect,selectively actuated multi-shape memory effect and functional systems of SMPs by using small molecule modified poly??-caprolactone?,ethylene-vinyl acetate copolymer,styrene-butyl acrylate copolymer and epoxy resin matrices.And we discussed all the intelligent polymers from their structures,thermodynamics,and mechanisms.A novel type of shape memory polymer nanocomposite was fabricated by thermal initiation of benzoyl peroxide?BPO?,which used chemically cross-linked poly??-caprolactone?with allyl alcohol as the matrix and Fe₃O₄ nanoparticles decorated conductive multiwalled carbon nanotubes?Fe₃O₄@CNT?as a magnetism and electricity responsive source.The nanocomposite exhibited excellent shape memory performance with a multistage stimulus recovery from a temporary shape to a permanent shape,triggered by an alternating magneticfield,an electric field and hot water,respectively.Uniquely,the nanocomposite also displayed significant two-way shape memory behavior under constant load conditions,which was not demonstrated previously.In addition,an alamar blue assay was also used to prove that the material possessed good biocompatibility.The results showed that the material could have good potential application in sensors,functional tissue engineering constructs and artificial muscles.A novel polymer composite with excellent light-actuated two-way shape memory effect?2W-SME?was fabricated using poly?ethylene-co-vinyl acetate??EVA?as matrix and p-aminodiphenylimide?p-AP?as both light-absorber and heat source?EVA/p-AP?.Unlike traditional thermally-driven two-way shape memory polymers,in our concept,the EVA/p-AP featured remotely controlled and light-manipulatable two-way shape memory behaviors.Utilizing the distinct light-responsive behavior of p-AP in the irradiation of 365 nm ultraviolet?UV?light,the EVA/p-AP composite exhibited excellent light-actuated 2W-SME by a light-manipulated procedure.The results from this study indicated that the composite material could have greatly potential applications in soft reversible drivers.A new type of multi-response composite styrene-based shape memory polymer?SSMP?structure was fabricated using multi-response composite method.This new SSMP structure included three regions:a SSMP matrix filled with multiwalled carbon nanotubes?SSMP-CNT?,a SSMP matrix filled with Fe₃O₄ nanoparticles?SSMP-Fe₃O₄?,and a third neat SSMP region which is located between the two composite regions.Differential scanning calorimetry?DSC?and dynamic mechanical analysis?DMA?results demonstrated that all the three SSMP materials possessed two well-separated transitions,which were subsequently used for the fixing/recovery of two temporary shapes?triple-shape memory effect?in each region.Furthermore,the unique selective actuation functionality of the multi-response composite structure was demonstrated,based on the principle that Fe₃O₄nanoparticles and CNT can selectively induce heat in a 30 kHz alternating magnetic field and 13.56 MHz radiofrequency,respectively.Therefore,the well-controlled multiple shape recoveries of the SSMP multi-response composite structure were achieved by applying selective stimuli.In addition,this proposed approach of selective actuations can be applied to other stimuli-responsive material systems to realize controllable deformations for some specific applications.Shape memory polymers?SMPs?are expected to play more and more important roles in space-deployable structures,smart actuators,and other high-tech areas.Nevertheless,because of the difficulties in fabrication and the programmability of temporary shape recovery,SMPs have not yet been widely applied in real fields.It is ideal to incorporate the different independent functional building blocks into a material.Herein,we designed a simple method to incorporate four functional building blocks using the unique chemical properties of epoxy resin:a neat shape memory epoxy-based?neat SMEP?resin,an SMEP composited with Fe₃O₄?SMEP-Fe₃O₄?,an SMEP composited with multiwalled carbon nanotubes?SMEP-CNT?,and an SMEP composited with p-aminodiphenylimide?SMEP-p-AP?into a multi-response composite structure,in which the four region surfaces could be programmed with different language code patterns according to a preset command by imprint lithography.Then,we aimed to reprogram the initially raised code patterns into temporary flat patterns using programming mold that,when triggered by a preset stimulus process such as an alternating magnetic field,radiofrequency field,365 nm UV,and direct heating,could transform these language codes into the information passed by the customer.The concept introduced here will be applied to other available SMPs and provide a practical method to realize the information hiding and reappearing.