Preparation Of Temperature And Electric Field Dual Response Smart Materials And Their Rheological Properties

Smart materials refer to those materials which have a certain perception of external or internal environmental stimuli?such as light,electric field,magnetic field,chemistry,temperature,machinery,etc.?,and can analyze,process and judge those stimuli.When the stimuli disappears or changes,smart materials can be reversibly restored to its original state.In recent years,with the development of smart materials and the practical application of materials for multiple performance requirements,dual or even multiple responsive materials have gradually entered people's field of vision and become a research hotspot.Poly?N-isopropylacrylamide?is a very typical temperature responsive material.Due to the hydrophilic and hydrophobic groups in the structure,temperature changes affect its hydrophilicity,causing changes in structure and properties.In this study,a copolymer of N-isopropylacrylamide monomer and an allyl imidazole-type ionic liquid monomer obtained a copolymer with double response to electric field and temperature,and control the hydrophilicity of ionic liquids by changing the type of counter ion in the ionic liquid.Further,the electrorheological properties of copolymers in silicone oil and their temperature responsiveness in water and silicone oil were investigated in this study.Firstly,copolymers containing hydrophilic counterion?Cl^-?and hydrophobic counterion?PF₆^-?were prepared.Their morphology,chemical structure and thermal stability were studied by SEM,NMR and TG.Then the rheological properties of the two polymers under electric and temperature fields were investigated.Under the action of no electric field,the copolymer exhibits a similar liquid-solid phase transition with increasing temperature in water.But in silicone oil,only the modulus caused by the swelling of the chain increases with temperature.At 20°C,the PF₆^-counter ion copolymer exhibits a more excellent electrorheological effect in silicone oil.As the temperature increases,the yield stress of the copolymer with PF₆^-counter ion increases first and then decreases,while Cl^-the yield stress of the counter ion copolymer has been increasing,so that the copolymer containing Cl^-counter ion exhibits a superior electrorheological effect in the silicone oil at a high temperature.Under the electric field,the two polymer particles disperse in the silicone oil and exhibit considerable electrorheological effect,but the PF₆^-counter ion copolymer is more easily dissociated into the silicone oil due to the hydrophobic effect of the PF₆^-ion and the lower dissociation energy,leading to an increase in current and a decrease in the flexion force.