Synthesis,Properties And Photo Processing Of Hexaarylbiimidozole Crosslinked Polymers Based On Click Polymerization

Photochromic molecules as a special class of photoresponsive materials,accompanying with the“on”and“off”actions,not only the primary color is changed,but also other physical properties such as absorption spectra,conductivity,fluorescence spectra,redox potential,electron paramagnetic resonance signals,dipole moment,spatial structure and so on are reversibly changed.Among them,based on the characteristics of visible light?<500 nm?can change photochromic materials'spatial structure,while we introduce the photochromic unit into polymer material system,the molecular level photochemical reactions could be transformed into macroscopic behaviors through elaborate molecular design.Therefore,as a class of smart materials,it exhibits huge application prospects as self-healing materials,micro-controllers,software robots,3D printing materials.Hexaarylbiimidozole?HABI?as an important photochromic molecule,the study of the small molecules has approtheached maturity;however,the study of related polymer materials is in its infancy.The performance of the related materials is poor due to the designed material structure is rough,and the application is not deep enough.More importantly,some of potential applications such as light-controlled processing and light-controlled mechanical changes are not available to be involved.Therefore,the design and synthesis of novel polymers based on hexaarylbiimidozole with excellent performance from the source are crucial.Based on this,the polytriazole-hexaryldiimidazole crosslinked polymers were designed and synthesized in this dissertation,and their photoresponsive properties were also studied systematically.In addition,we explored their applications in self-repaired,light-controlled processing,light-controlled mechanical changes and light-controlled microscopic morphology rearranges.It mainly comprises four works as the following list:?1?To achieve the greatest degree of deformation due to photochemical reaction of hexaarylbiimidazole,we introduce the ortho-halohexylbiimidazole?o-Br-HABI?unit with excellent anti-fatigue properties into the polymer materials as crosslinking agent.Specifically,HABI units are connected with four propargyl groups by covalent band to form bridged hexaarylbiimidazole crosslinking agent and non-bridged hexaarylbiimidazole crosslinking agent.In addition,the structures and discoloration properties of crosslinking agents are investigated in detail.Finally,non-bridged hexaarylbiimidazole crosslinking agent is selected for the synthesis of subsequent polymer materials.?2?It is very common for materials to convert between liquefaction and solidification during thermal phase transition.However,the design and synthesize of polymer materials,which could achieve solid-liquid transition under isothermal condition is more challenging.In this dissertation,we have synthesized PTA-HABI polymer with dipropargyl-PEG₁₀₀₀ as hydrophilic unit,1,6-diazidohexane as linker and tetrapropargyl-HABI as crosslinker.It is visible to naked eyes that the PTA-HABI polymer gel simultaneously shows color changes and evident deformation from solid to liquid state upon light irradiation,which is attribute to sophisticated design of the polymer architecture.In addition,the optomechanical response of PTA-HABI photoplastic elastomer is demonstrated by stress-strain experiment.?3?There are many smart materials that have single function,but one smart material is highly integrated with multiple functions at the same time is very rare.Interestingly,based on the deformation properties of polytriazole-hexaarylbiimidazole?PTA-HABI?materials,we achieve a series of light-controlled applications,“melting”,“cutting”,“drilling”and“remolding”,the photo-alignment of the PTA-HABI gel network demonstrates that the oriented surface patterning is directed by light.In addition,data shown that PTA-HABI photoplastic elastomers exhibit excellent self-healing behavior under the synergy of white light?optical power density 5 mW/cm²?and heat?25-30??for24 h.?4?It would have broader applications if HABI units are integrated into more types of functional materials.we have synthesized a double-crosslinked PTA-HABI-TPE elastomer,which has characteristics of having both dynamic covalent crosslinking point and fixed crosslinking point.Studies have shown that the material has more excellent self-healing properties.In addition,a universal synthetic plastic-elastic reversible material switching design concept was proposed,and a practical verification was performed using the PTA-HABI-TPE elastomer model.In addition,a universal design idea for synthetic photoplastic spring capable of reversible switchable between plastic deformation and elastic deformation is proposed.In this dissertation,we fabricate a prototype based on dual crosslinkers of HABI and TPE,the synthesized photoplastic spring exhibits photoswitchable plastic strain behavior,i.e.,the plastic strain is transformed into elastic strain upon light irradiation.