Synthesis Of Polyurethane With Quadruple Hydrogen Bonds And Photothermal Study Of MXene Composite Films

In the past three decades,supramolecular chemistry has been focused due to its unique properties,which are different from those of conventional polymers.Becauce there are dynamic and reversible self-assembled functional monomers in the polymers,supramolecular polymers are able to responsive to external stimuli（heat,light,p H,etc.）,which broadening the possibility of developing a new generation of smart functional materials,especially for the preparation of self-healing materials.At present,the best supramolecular system based on quadruple hydrogen bonding is the UPy system.In this thesis,the UPy quadruple hydrogen bonding dynamic reversible crosslinking network was introduced to the side chain of polycaprolactone-polyurethane（PCL-PU-UPy）.And then,a lot of work were take to explore the effect of UPy on the toughening of PCL-PU-UPy;meanwhile,a photo-thermal responsive composite film was prepared by a simple blending method,which aims to develop a smart material that can be remotely photo-controlled driven and self-healing.The main research contents and results of this thesis are as follows:1.Using polycaprolactone with excellent biodegradability as the soft segment,a polycaprolactone-based polyurethane supramolecular polymer with UPy moieties in the side chain was carefully designed and synthesized.First,the A-UPy chain extender was synthesized by a two-step method,and then introduced into the polycaprolactone-type polyurethane prepolymer in different proportions to prepare a quadruple hydrogen-bonded polycaprolactone-type polycaprolactone type containing UPy units in the side chain.The prepared A-UPy chain extender and PCL-PU-UPy supramolecular polymer were both the target products through the analysis of hydrogen nuclear magnetic resonance（~1H NMR）and Fourier transform infrared spectroscopy（FTIR）.Differential scanning calorimeter（DSC）,thermogravimetric analyzer（TGA）and other test results show that the introduction of UPy greatly reduces the crystallinity and thermal stability of the polymer.In order to explore the toughening effect of UPy dimer,the tensile test of the sample was carried out.The results showed that the introduction of UPy greatly improved the mechanical properties of the sample.The pure sample increased by 2.3 times.2.Fragmented 2D MXene sheets were prepared by etching method,and then added to PCL-PU-UPy（PPU）supramolecular polymer by solution blending method to obtain PPU-MXene composite films.Due to the excellent thermal conductivity of MXene,the sample has good photothermal response properties that can be remotely manipulated.Under the irradiation of NIR laser,the real-time temperature of the sample surface was tracked and recorded by a thermal imager,and the effect of different MXene contents on the temperature rise was systematically explored.Under the light intensity of 100 m W/cm~2,the saturation temperature of the samples were all higher than 120°C.When the MXene content was 1%,the saturation temperature of the sample was as high as 135.6°C,and the temperature rapidly increased to 41.6°C at a heating rate of about 4°C/s within 5 s.At the set temperature of 60°C,the data density intuitively shows that the time required is shorter as the MXene content increases.Different temperature programmed control and cycle tests were carried out,and the data showed that the composite membrane had excellent stability and controllability.The self-healing test was carried out under NIR,and the recovery of the self-healing morphology indicated that the sample had a good remote light-controlled self-healing performance.This indicates that the remotely steerable photothermal responsive composite film broadens the application scenarios of soft robotics and artificial muscles.