Study On Thermochromic Behavior Of Polydiacetylene/Metal-Organic Framework Compound Composites

Polydiacetylene（PDA）is a conjugated polymer with unique structural and optical performance,suitable for design as a biological/chemical sensor.However,under temperature stimulation,the color change of polydiacetylene is irreversible,which is not conducive to repeated detection or monitoring as a temperature sensor.To improve recycling,this paper prepared polydiacetylene/metal-organic framework compound composites,the reversible thermochromism of polydiacetylene was achieved,the main research contents and results are as follows:（1）Self-assembly of 10,12-Tricosadiynoic acid（TCDA）and metal-organic framework compound（MOF-5）,and irradiation under 254 nm ultraviolet light to form a dark blue poly（TCDA）/MOF-5 composites.The structure,morphology,size and thermal properties of the materials were characterized by FT-IR,XRD,SEM,DLS,TG and DSC,the effects of polymerization time and the mass of MOF-5 on the reversible thermochromism of poly（TCDA）/MOF-5 composites were explored.The experimental results showed that the optimal photopolymerization time of the composites was 10 min,the optimal mass ratio of TCDA and MOF-5 was 5:2,the color transition temperature was 70℃,and the color of aqueous solution showed reversible color transition from blue to fuchsia at 30⁹5℃.There are two steps for reversible transition of poly（TCDA）/MOF-5 polyvinyl alcohol film,that is,the reversible transition from room temperature to 130℃is blue and magenta,and the reversible transformation from 140℃²00℃is orange and orange-red.This composite is mixed with yellow dye,the prepared green polyvinyl alcohol film exhibited reversible transition from green to orange-red at room temperature to130℃.（2）Using 10,12-Tricosadiynoic acid（TCDA）and MOF-177 as materials,Poly（TCDA）/MOF-177 composites were prepared by ultraviolet irradiation.The structure,morphology,size and thermal properties of the composites were characterized,and the effects of polymerization time and different mass on reversible thermochromism of the composites were investigated in detail.The color of the composite solution exhibits a rapid and reversible change of"blue?rose red"between 30⁹5℃,and the number of reversible cycles of heating-cooling can reach more than 300 times,which has good stability.The prepared poly（TCDA）/MOF-177 polyvinyl alcohol film can achieve reversible thermochromic of polydiacetylene at high temperature,and the film can return to the original color instantly after leaving the heat source.（3）The metal organic framework compound Zn₃（BTC）₂ was self-assembled with 10,12-Tricosadiynoic acid（TCDA）and 10,12-pentacosadiynoic acid（PCDA）,respectively,and then polymerized to obtain reversible thermochromism composites.XRD,FT-IR,Raman,SEM were used to characterize the structure and morphology of the composites,the effects of metal-organic framework compounds prepared with different central metal ions on reversible thermochromism behavior of polydiacetylene were explored by combining color change photos and UV-vis absorption spectra.The effects of the number of carboxyl groups in MOFs materials on the reversible thermochromism behavior of PDA/MOFs composites and the effects of polydiacetylene with different chain lengths on the color transition temperature were analyzed.The experimental results showed that the bridging bidentate coordination formed between Zn²⁺and PDA head group in the metal-organic framework compound determines the fast reversible thermochromism behavior of PDA.