Functional Regulation And Application Exploration Of POSS-based Porous Polymers

As a new type of organosilicon functional material,organosilicon porous materials have outstanding advantages such as various synthesis methods,high and low temperature resistance,controllable structure and good thermal stability and thus they have been rapidly developed and find many applications in traditional fields such as gas adsorption and separation,catalysis,sensors,and adsorption.Polyhedral oligomeric sesquisiloxanes(POSS)as a typical monomer used in the synthesis of organosilicon porous materials,have the advantages of low backbone density,strong oxidation resistance,good mechanical properties and biocompatibility.In particular,they have been proved to be an ideal class of monomers for the contruction of fluorescent porous materials.POSS can maintain the material stable porous skeleton because of the rigid structure,and can also prevent the fluorescence quenching caused by the aggregation of fluorescent monomer,thereby maintaining stable fluorescence.However,the exploration of the functionality tunability and applications of POSS-based fluorescent porous polymers is still limited.Therefore,this thesis aims to explore the functionality construction and applications of POSS-based fluorescent porous polymers by carrying out the following two aspects.1.HPP-SH can be readily synthesized by Heck reaction of octavinylsilsesquioxane and 4,4’-dibrombiphenyl,and subsequent post-functionalization by a thiol-ene click reaction with 1,2-ethanedithiol.These materials exhibit high thermal stability and adjustable porosity.The introduction of abundant thiol and thioether groups in the porous networks imparts the material ability to effectively capture Hg2+ions by the coordination interaction,while this interaction can also trigger the fluorescence quenching,thereby realizing the detection of Hg2+ions.The HPP-SH exhibited adjustable detection limits by investigating the effect of sulfur content on the detection of Hg2+ions.It was found that HPP-SH has high sensitivity and selectivity towards Hg2+ions with a low limit of detection of 4.48 ppb,as well as high selectivity and an adsorption capacity of 900.9 mg/g,and the adsorption process fits well with the pseudo-second-order kinetic and Langmuir model,indicating the monolayer and chemical adsorption process.These results reveal that this material can be utilized as a promising candidate for the selective detection and adsorption of Hg2+ions in the aqueous solutions.2.Based on the previous work,octavinylsilsesquioxane reacts with 4,4’-dibromobiphenyl or 1,3,6,8-tetrabrom-opyrene by Heck reaction,resulting in two fluorescent porous polymers,HPP-1 and HPP-2.It was found that the Commission Internationale de L’Eclairage(CIE)coordinate for HPP-1 was(0.15,0.11)in the blue light region,while the CIE coordinate for HPP-2 was(0.51,0.36)in the red light region by measuring the fluorescence properties of the materials.Therefore,simple physical doping of two fluorescent materials was performed to modulate white light in solution,solid state and organic light-emitting diodes(OLED),and the effects of conditions,such as solvent and excitation wavelength on white light modulation,were investigated.It was found that different excitation wavelengths can modulate the intensity of fluorescence emission and realize the emission of white light at different excitation wavelengths.In addition,by changing the doping ratio of HPP-1 and HPP-2,OLED with CIE coordinates at(0.42,0.36)were obtained with a color rendering index(CRI)of 90 and a correlated colour temperature(CCT)of 2858 K,thus achieving warm white light emission.These results indicate that POSS-based fluorescent porous materials have good potential for application in white LEDs.