Electrospinning And Characterization Of Shape Memory Polymer Microfiber Films

Shape memory polymers(SMPs)can return their original shape from the temporary shape when exposed to environment stimuli.The advantages of SMPs includes large deformation and strong recovery force,etc.As a kind of emerging active shape changing materials,SMPs have a broad range applications,such as smart textiles,biomedical science,intelligent robotics,aerospace,flexible electric devices,optical devices,information carriers and so on.With the development of science and technology,practice applications require more and more complex and various smart materials as well as structures,in particular,small size devices and remote control actuation methods,which greatly promotes the research of nano/micro-size structure SMPs and their composites.On this motivation,the aim of this project is to design and propose nano/micro-size SMPs and their composite fibrous films,including fabrication of shape memory fibers by electrospinning,demonstrating the fibrous and porous structure SMPs with multiple shape memory effect and functionality.Moreover,the remote controlling shape recovery behavior in magnetic fields is investigated.Electrical field induced shape memory composite films are fabricated and the shape recovery behavior is studied.Furthermore,composite fibers with core/shell structure are fabricated by co-electrospinning.The microstructure,thermal property,mechanical property,chemical stable performance were systematically investigated and analyzed by SEM,TEM,DSC,TGA,FTIR,Nanotensile machine,XRD,DMA,etc.The research promotes the development of SMP nano/microfibers.Non-woven porous microfiber membranes with multiple-shape memory effect were prepared by electrospinning.The resulting fibrous membranes showed good and continuous fibers by adjusting the electrospinning process parameters.Adding PEO with 0.3% to 1.0% in the Nafion solution can effectively change the diameters of fibers.The glass transition temperature range was from 55 to 170 ℃,which played a key role on multi-shape memory effect.The effect of heat treatment on the inner microstructure was also investigated.The heat treatment improved the structure stability of fibrous membranes.The results showed that,PEO did not affect the chemical property of Nafion.With the increasing of PEO,the shape fixity ratio of fibrous membranes increased and shape recovery ratio decreased.Furthermore,multiple-shape memory effect of electrospun microfiber membranes was demonstrated,including dual-,triple-,quadruple-,and quintuple-shape memory effect.Based on the above work,the magnetic particles filled multiple shape memory composite microfiber membranes were prepared by electrospinning.The magnetic particles Fe3O4 was distribute in the fibers,providing the excellent magnetic property.To demonstrate the repeatability of fibrous membranes,five consecutive shape memory cycles were carried out and the shape fixity and shape recovery ratios were all above90%.The Nafion/Fe3O4 composite film recovered its original shape within 16 s triggered by magnetic field.The properties of magnetic particles filled multiple shape memory composite fibrous membrane and magnetic field actuation effect of electrospun multiple shape memory composite fiber membranes were investigated.The effect of magnetic particle amount and magnetic fields intensity on magnetic field activated quintuple-shape memory effect was analyzed.The recovery time decreased with the increasing of output power.Inconsideration of the uniform distribution of fillers in polymer matrix,the electrospun PAN based carbonization microfiber membranes filled shape memory composites materials were investigated.PAN nanofibers were fabricated by electrospinning.After stabilization(290 ℃)and carbonization(1000 ℃)treatment,the carbon nanofibers membranes with porous structure were obtained.Combining the carbon nanofiber membrane with shape memory polymer matrix,the shape memory composite films were fabricated.The conductivity decreased from 12.30 S.cm-1 to 8S.cm-1 by increasing the electrospinning voltage from 20 kV to 30 kV.Moreover,the PAN based carbon nanofiber membranes filled shape memory composite fibrous materials were triggered by electrical field,and the fibrous film realized 100% recovery when applied 14 V voltage.The temperature distribution of composite film was recorded and analyzed by infrared thermography.Thermoplastic polycaprolactone was served as template.Thermosetting epoxy was used as core material.The co-electrospinning method was used to fabricate the shape memory microfibers with core/shell structure.The effect of electrospun solution speeds on the microstructure of core/shell fibers was investigated.SEM and TEM were applied to characterize the core/shell structure and the mean diameter was 1200 nm.In addition,the mechanical property was analyzed.Compared with the electrospun PCL fibrous membranes,the Young’s modulus of composite fibrous membranes increased by 24%.This design provided a method for thermosetting polymers without spinnability to fabricate fibers.Furthermore,the micro-level and macro-level shape memory effect was demonstrated.