Preparation And Electromechanical Properties Of Dielectric Elastomer Composites With High Actuated Strain

Dielectric elastomer(DE)is a kind of electroactive polymers,which can be changed its size and shape under the condition of electric field and be resumed its original shape rapidly when the electrical stimulation is removed.A wide range of applications have been proposed based on DE,such as soft actuators,large strain capacitive sensors,optical devices,health monitors,and energy harvesters.The electromechanical properties can be improved by increasing dielectric constant,increasing electrical breakdown field,and/or decreasing elastic modulus.Nitrile rubber(NBR)has a high dielectric constant(almost 10),because of a lot of acrylonitrile groups which are easy to be polarized in macromolecular chains.Dopamine(DOPA)is a protein substance secreted by mussels,which can polymerize to poly(dopamine)(PDA)itself in almost every substrate surface.As is shown in chapter three,a special core/shell structure of dielectric nano-particles were prepared by biominimetic modification(denoted as Ti02-PDA).Then different amounts of TiO2 and Ti02-PDA were added into NBR matrix to prepare dielectric elastomer composites.The results showed that the microstructure,dielectric properties,and electromechanical properties were improved by DOPA.At last,10 phr TiO2-PDA/NBR dielectric elastomer composites showed the biggest actuated strain.In chapter four,we prepared an all-organic non-percolative dielectric composite by adding polyaniline(PANI)and epoxidized soybean oil(ESO)into NBR matrix by adjusting molecular interaction.PANI was used to increase the dielectric constant,while ESO was used to decrease the elastic modulus of the composite.Finally,NBR composite filled with 4 phr PANI and 50 phr ESO displayed an actuated strain of 2.5%was obtained at 4.5 kV-mm-1.In chapter five,in order to improve electromechanical properties of silicone rubber(SR),high-dielectric-constant BaTiO3(BT)particles and plasticizer of silicone oil(SO)were introduced.Because the dielectric constant was increased by BT and entanglement of molecular chains was decreased by SO,the electromechanical sensitivity of SR improved was largely.At last,the SR composites filled with 20 phr BT and 50 phr SO showed the largest actuated strain.