Synthesis And Applications Of Hypercrosslinked Microporous Polymers With Controlled Morphology

Microporous organic polymers(MOPs)with high surface area and abundant microporous structure represent a novel kind of porous materials which can be constructed from pure organic building blocks.Due to their unique properties such as low skeleton density,high physical/chemical and thermal stability,devious synthetic routes,easy functionalization with controlled pore topology,these materials show promising applications in adsorption,separation,catalysis,sensing,energy storage and conversion and thus becoming a hotspot in polymer material science field.MOPs are normally classified as polymers of intrinsic microporosity(PIMs),conjugated microporous polymers(CMPs),covalent organic frameworks(COFs)and hypercrosslinked polymers(HCPs).Compared with other MOPs,HCPs are mainly prepared by Friedel-Crafts alkylation reaction which can be low-cost and large-scalable.The pore structure of HCPs is generated from the non-dense packing of the rigid polymer chains.At present,a great deal of researches have been focused on the synthesis and functionalization of HCPs.However,the investigation into the design and synthesis of HCPs with controlled micromorphology in both macroscopy and microscopy is very rare.In addition,the synthesis of HCPs with 2D ordered structure and long range conjugation is always a challenge.Therefore,the preparation of HCPs with different morphology,the investigation of the relationship between HCPs morphology and performance as well as the construction of HCPs with conjugated and ordered structure will be the new directions for the development of HCPs.Based on the external knitting strategy,this thesis describes the design and preparation of HCPs with various morphology and functionality by using different functional monomers and polymerization methods.The inner molecular structure,morphology and properties of HCPs were characterized by FTIR,solid state NMR,XPS,SEM,TEM,N2 sorption analysis and so on.Moreover,their applications in adsorption,heterogeneous catalysis and photoelectricity field are also discussed.The main contents of the thesis are as follows:Chapter 1 summarizes the development of HCPs including three main synthetic methods for HCPs,introduction of HCPs with different morphology and their applications in adsorption,separation,catalysis,drug release,sensing.Chapter 2,3D hierarchical porous monoliths were prepared by FDA knitting of macoporous monolith precursors which were obtained by polymerization of high internal phase emulsion templates(polyHIPEs).After knitting,these hypercrosslinked monoliths showed high surface area with hierarchical porous structure consist of interconnecting macropore from the precursor and abundant micro-mesopore from knitting process.By adjusting the DVB concentration in monomer mixture,the resulting surface area and porous structure can be easily controlled.These hypercrosslinked monoliths not only showed comparable H2 and CO2 adsorption properties,but also can rapidly remove organic solvent from water owing to their superoleophilicity and showed large adsorption capacities.Chapter 3,pyridine-functionalized hierarchical porous monoliths were prepared and used as platform to load different metal nanoparticles forming monolithic heterogeneous catalysts.The functionalized monolithic precursors were prepared by copolymerization of 4-vinylpyridine and styrene using HIPE templates.Then,the FDA knitting process was adopted to form hierarchical porous structure with high specific surface area.The functionalization degree of the monoliths can be adjusted by changing the monomer ratio of 4-vinylpyridine to styrene.With the increased functionality,the surface area of the resulting monoliths decreased,however,the CO2 adsorption performance increased.The loading of different metal nanoparticles was realized by NaBH4 reduction and heating reduction methods respectively which resulted nanoparticles with different size.Moreover,the particle size and size distribution can also be controlled by using different functionalized monoliths or changing the metal ions concentration.The monoliths loaded with Au nanoparticles were used as heterogeneous catalyst for the reduction of 4-nitrophenol with high efficient and good recyclability.Compared with those catalysts in powder state,the monolithic monoliths can be easily separated and directly applied in the following recycling reactions.Chapter 4,a novel self-templated strategy was presented for the fabrication of microporous polymer hollow capsules.Firstly,the core-shell nanosphere precursors with PS core and partially DVB crosslinked PS-DVB shell were obtained by a two-step emulsion polymerization.Then,the PS core was removed by THF etching to produce hollow structure.After knitting,the microporous hollow capsules were obtained with high surface area.By change the reaction conditions of emulsion polymerization,the particle size of the hollow capsules can be adjusted;by adding DVB at different time period,the inner hollow cavity and shell thickness can be tuned as well.The resulting microporous hollow capsules showed good H2 and CO2 adsorption properties,and they can also be used as solid absorbents to rapidly remove micropollutants in water such as rhodamine B and methyl orange.In addition,functionalized microporous hollow capsules were prepared by incorporating 4-vinylpyridine functional monomer.After loading Au nanoparticle,the hollow capsules were used as heterogeneous catalysts for efficiently catalyzing the reduction reaction of the 4-nitrophenol.Chapter 5,a new strategy was developed to construct a series of hypecrosslinked polymer networks with conjugated structure.In this strategy,dimethoxybenzene was chosen as the novel external crosslinker which directly linked several kinds of aromatic compounds resulting hypercrosslinked networks with different surface area and pore structure.With high surface area,these materials exhibited comparable good adsorption properties for H2 and CO2.The benzene rings in crosslinkers not only provide rigid linking bridges between the building blocks but also extend the conjugation from the monomers thus resulting a long-range conjugated network.As a result,these materials exhibited bright blue fluorescence and p-type semiconductor properties.