Preparation And Characterization Of Photoresponsive Polymer Self-healing Materials Based On Azopyridin

With the rapid development of artificial intelligence,5G and advanced manufacturing,the necessity of advanced materials is also improving.In particular,the demand for intelligent polymer composites with self-detection,self-healing,multi-condition work functions will also become the main direction of industry integration and upgrading and future development.In recent years,polymer-based self-repairing materials have attracted much attention from researchers and industry field,and have shown wide application prospects in the fields of human monitoring,electronic skin and man-machine interaction.The design and preparation of self-healing functional polymers and their combination with wearable devices have become one of the most popular and active directions in the field of materials science.This paper represents the design and regulation of polymer elastomer,introducing supramolecular metal-ligand motifs with photoresponse performance,and endows excellent light-healing properties under different conditions.Then,the property of photo-healing in this system was deeply verified by experiment and theoretical calculation.In addition,we had combined this elastomer with nano-conductive network structure for strain sensor with photo-healing properties,which utilized the activation of cellulose nanocrystals(CNC)and carbon nanotubes(CNTs)to build micro cracks of conductive structure and it can be quickly damaged and reconstructed under the change of strain.And the prepared sensor can realize rapid and accurate detection of identification of the function of body.The main research contents and conclusions are as follows:(1)Polymer with photoresponse property(Abpy-pdms)was prepared by introducing azopyridine,a photoresponsive functional group,into the structure of commercial polydimethylsiloxane.The ratio of metal ions to ligand was determined by ultraviolet titration.Subsequently,metal ions(Cu2+,Eu3+,Zn2+)were introduced into Abpy-pdms to prepare Cu(Abpy)2-PDMS,Eu(Abpy)2-PDMS and Zn(Abpy)2-PDMS based on reversible metal coordination bonds.These three kinds of materials show different mechanical properties and self-healing properties.The breaking elongation of the three in the initial state is 62%,351%and 460%respectively.After the cut/light-repair process,their photo-healing efficiencies were 55.7%,54.4%and 95.6%respectively.Furthermore,we further discussed the optical repair performance of Zn(abpy)2-PDMS in underwater,low-temperature environments and multiple optical repair.The results showed that the photo-healing efficiency was 56.4%and 67.6%respectively in underwater and low-temperature environments,and the remediation efficiency was still as high as 93.4%after three times light remediation.As for the heat generated during the photo-repair process,we designed a relevant simulation experiment,which proved that the"contribution" of this part to the photo-repair process was almost negligible.(2)Firstly,we had built the model of the azo pyridine ligand to metal ions.With the help of the experimental and theoretical calculation methods from several aspects,the photo-repair mechanism of this system was demonstrated.We supposed that the cis/trans isomerization of azo pyridine near the healing interface under light stimulus bridge the mutual penetration of polymer chain in rupture interface,realize the metal coordination bond to reform,to achieve the objective of self-healing.We illustrate the changes between azopyridine and metal ions in the process of photoisomerization by Ultraviolet absorption,1H NMR and VASP.The results show that the light source in the ultraviolet band(365 nm)can realize the photoisomeric transformation of azopyridine ligands from trans structure to cis structure and the fracture of metal coordination bond.On the contrary,the light source in the blue light band(450 nm)can make the cis azopyridine back to the trans structure and reform the metal-ligand bonds.Through these two processes,the photo repairing of the polymer is realized.This work provides new ideas and methods for the design and preparation of related optical response smart materials and photo-healing materials.(3)By combining the prepared photo-healing supramolecular elastomer Zn(abpy)2-PDMS with the nano-conductive network layer,a novel photo-repairing strain sensor was prepared.The conductive microcrack structure constructed by activated cellulose nanocrystals(CNC)and carbon nanotubes(CNTs),which can be destroyed and reconstructed rapidly under the change of strain and showing higher sensitivity and faster response.The sensors produced by our supramolecular elastomer also exhibit excellent mechanical/sensing repair properties.Even after 10 cut/repair cycles,the sensor signal remains consistent with the original sample.This flexible,highly stretchable and photo-repairing strain sensor has a wide range of materials and a simple preparation process,which provides a new design and preparation method for the preparation of a series of related optical smart materials and strain sensors in the future.