Synthesis And Application Of Lotus Root-like Polymers With Hierarchical Porous Structure

Scale up preparation of porous polymers with high specific surface area and fast mass transfer rate is a challenge.The research and development of such porous polymer materials have important scientific significance and broad application prospect.Lotus root is a type of natural biological materials with hierarchical porous structure,meaning it contains two kinds of pore structures,i.e.three-dimensionally ordered pores with centimeter-sized and smaller-sized pores in the wall of the lotus root,respectively.The former is conducive to gas transfer,and the later is conducive to transmission and absorption of organic nutrients.These two types of pores have different shapes and functions.The unique hierarchical porous structure of lotus root provides a new idea for design of new porous polymers.In this dissertation,we propose the use of organic solvent crystal porogens in combination with other porogenic methods to prepare biomimic micro-nano sized porous materials,and to investigate enrichment and separation of oil-water emulsions,carbon dioxide,and environmental pollutants.The specific research content is as follows:1.Preparation of superamphiphilic cryogels and their application in separation of oil-water emulsions.A series of cryogels were obtained by free radical cryo-polymerization,using dimethyl sulfoxide(DMSO)as solvent and crystalline porogen,hydrophilic polyethylene glycol diacrylate(PEGDA 600)as monomer and cross-linking agent,and hydrophobic polydivinylbenzene(PDVB)microspheres as additives.The effects of varying mass ratios of PDVB to PEGDA on the morphology of the resulting materials and the separation of the oil-water emulsion were investigated.The results show that the obtained composite cryogels have micron-sized macroporous structure with pore size ranging mainly from 1 to 100 μm.The resultant cryogels displayed superamphiphilicity in air,superhydrophilicity under oil,and oleophobicity under water.When the mass ratio of PDVB to PEGDA is 1:2,the resulting composite cryogel has a rapid separation rate and high separation efficiency for the oil-water emulsion.The separation process was performed by gravity alone without the need of an external pressure device,and no significant change was observed in the separation after repeated use of 8 times.2.Preparation and adsorption of supermacroporous poly(divinylbenzene)cryogels withhigh specific surface area.Hierarchical porous materials were prepared by cryo-polymerization combined with solvothermal post-crosslinking.Firstly,divinylbenzene(DVB)was used as the monomer,DMSO was used as the solvent and its crystals were used as porogens.The macroporous cryogel was obtained by free radical cryo-polymerization,and the cryogel was used as the precursor,dichloroethane was used as a solvent and the cryogel was post-crosslinked by free-radical polymerization and Friedel-Crafts reaction under solvothermal conditions,thereby generating nanoscale pores on the basis of macropores and obtaining hierarchical porous polymers.The pore structure of the material was characterized by scanning electron microscopy and nitrogen adsorption experiments.The results show that the obtained material has not only micron-sized pores but also nano-sized pores.The obtained material was used for the storage of carbon dioxide and the adsorption and separation of aniline.The experimental results showed that the cross-linked material after the Friedel-Crafts reaction had a carbon dioxide storage capacity of 13.62 mmol/g(25 bar,273 K)and a maximum aniline adsorption capacity of 333.33 mg/g.3.Synthesis of fluorine-containing porous polymers by Friedel-Crafts cryo-polymerization.A series of hierarchical porous materials were prepared in one step Friedel-Crafts addition reaction at a lower temperature with the pore formation of organic solvent crystals.In the process,fluorostyrene was used as the functional monomer,DVB as a cross-linking agent and acetic acid as a solvent,acetic acid crystals as porogens,and anhydrous ferric chloride as a catalyst.The effects of different solvents,catalyst dosage,and the amount of functional monomer on the morphology and pore structure of the obtained materials were investigated.