Studies On Preparation And Properties Of Thermosetting Shape Memory Polyurethane And Its Composites With Photothermally Responsive

Shape memory polymers can fix temporary shapes and recover to their original shapes when exposed to external stimulation.They have broad potential applications in the fields of biomedicine,smart surfaces,and aerospace.As a kind of shape memory polymer,shape memory polyurethane has attracted wide attention in the fields of biomedicine,smart textile,etc.because of its large deformation recovery,easily processing,wide adjustable thermal transition temperature and general biocompatibility.However,the poor mechanical properties,single responsive mode and complicated preparation process of shape memory polyurethane limit its wide application.Here,this study uses biocompatible polycaprolactone diol as the soft segment,isophorone diisocyanate as the chain extender,and glycerol as the crosslinking agent.Thermosetting shape memory polyurethane with a thermal transition temperature at body temperature was prepared by a simple one-step method which is convenient for mass production,and its mechanical properties were improved and light responsive function was given by adding fillers.The main content and conclusions are as follows:（1）The effects of different soft chain molecular weights and crosslinking densities on the properties of shape memory polyurethane were studied.Fourier transform infrared spectroscopy showed that the polyurethane was successfully synthesized by one-step method.The transition temperature,crystallization status,and shape memory performance of the shape memory polyurethane synthesized with different soft chain molecular weights were compared.It was determined that the polycaprolactone diol with molecular weight of 2000 g·mol^-1 as soft chain had the best shape memory performance as well as better mechanical properties.Under the condition of–NCO:-OH=1:1,the crosslinking density is controlled by adjusting the ratio of polycaprolactone diol and glycerol,and the transition temperature,crystallization,storage modulus and shape memory performance of shape memory polyurethane with different crosslinking densities are compared.The results showed that the IPDI:PCL-2OH:GL molar ratio was 2:1.50:0.33,which had the best comprehensive performance.Shape memory recovery can be triggered at body temperature,a 450%recoverable strain can be maintained.（2）The mechanical properties of the matrix were improved by adding micro/nano cellulose,and the light responsive function was given by carbon black.The effects of different content of micro/nano cellulose fibers on the thermal,mechanical and shape memory performance of shape memory composites were studied.The results showed that the addition of micro/nano cellulose has no obviously effect on the transition temperature of the composite,nor will it hinder the shape memory function.The composites still has excellent shape fixation and recovery rate;In terms of mechanical properties,the addition of micro/nano cellulose can significantly improved the mechanical properties of the composites,and it has the best mechanical properties when the additive amount was 2wt%.the stress was increased by 60%under 100%strain at high temperature,meanwhile,can provide a recovery stress of 1.09 MPa and lift an object about 400 times of its own weight.The photothermal conversion efficiency and bending recovery rate of composites with different carbon black content were also studied,and shape memory cycle tests and cyclic stress-strain tests were carried out for the ternary composites.It was proved that the photothermal conversion efficiency is not linearly related to the amount of carbon black added.The composites with 1wt%carbon black added can be heated to its transition temperature in 16 s,and can recover from the folded state to fully unfolded in about 30 s.Finally,a space deployable box and a heavy lifting experiment were designed to show the effect of remote light control.