Stydy On The Mechanochromic Properties Of Intercalated Iso-aminobenzopyranxanthene Polymers

Mechanochromic polymers will change their color under the action of external force,which can be used in polymer stress sensing,damage detection and other fields,and thus have received more and more attention.The typical design of mechanochromic polymers is based on the embedding of mechrophores into the polymer chains,which change their optical properties when subjected to stress.The currently developed chromophores can only develop a single color under external stimuli.In order to display multiple colors,the method of embedding chromophores of different hues is generally used to adjust the hue,which has problems such as uneven hue.To this end,we designed and synthesized a chromophore with a double-spirosymmetric structure,which can switch three states,and embedded the chromophore into the polymer to achieve the effect of multicolor gradient transition.(1)An iso-aminobenzopyranxanthene(iso-ABPX)molecule with a double-spirosymmetric structure was designed and synthesized,and its responsive properties to light and physical stimuli in solution and solid conditions were investigated.Studies have shown that iso-ABPX molecules can change color in response to acid,light and external stimuli.(2)The iso-ABPX molecules were embedded in linear poly(methyl acrylate),the color-changing properties of the polymer solution under the action of ultrasound were investigated,and the mechanochemical reaction mechanism of the double spiro structure in the polymer was discussed.After ultrasonic treatment of linear polymethyl acrylate,its absorption spectrum shows a force-dependent change,and the magnitude of the force transmitted to the polymer chain can be adjusted by changing the length of the polymer chain.Through Co GEF simulation calculation and experimental study,it is determined that the double-spiro-ring structure in linear polymethyl acrylate changes directly from closed-loop to double-opened loop under the action of external force.Due to the thermal effect,the double-opened ring will partially become a single-opened ring,i.e.,a mechanothermal equilibrium,and the relative distribution of the single-opened and double-opened rings changes predictably with different applied forces,resulting in a multicolor gradient color transition,Finally,a theoretical model is constructed to describe the relationship between force and color in linear polymethyl acrylate.(3)The iso-ABPX molecules were embedded in polyurethane,and the response properties of polyurethane films to force,acid and light stimuli were investigated.Studies have shown that the color of the polyurethane film changes from light yellow to pink after being compressed or extruded;the color of the polyurethane film changes to red after acid fumigation;the polyurethane film is sensitive to 365 nm UV light,changes color rapidly and can recover color after heating.