Preparation Of Crosslinked Maleic Anhydride Copolymer Microspheres By Self-stabilized Precipitation Polymerization And Its Application

With the advantages of high specific surface area,low density,good diffusibility and mobility,and controllable physicochemical properties,monodisperse polymer microspheres show great potential in field of water treatment,chromatographic separation,immobilization of enzymes or antibodies,optical devices and drug delivery.However,the traditional methods for synthesizing monodisperse polymer microspheres still have problems such as dispersant/emulsifier residues,using complex methods for regulating the morphology of heterogeneous particles,and limited types of applicable monomers.To address the above problems,three types of crosslinked monodisperse multivinyl monomers（MVMs）-maleic anhydride（MAH）copolymer microspheres were prepared based on self-stabilized precipitation（2SP）polymerization without the use of any dispersant/emulsifier,and effective control of the microsphere morphology was achieved by simply changing the crosslinked monomer type and reaction medium.On this basis,hydrophilic microspheres with tunable crosslinking degree,high-performance adsorption microspheres for water treatment,and hydrophobic surfaces with micro-nano structures were prepared by modifying the abundant anhydride groups in the microspheres.The main research contents and results of the thesis are as follows:1.Monodisperse styrene-maleic anhydride-isoprene（St-MAH-IP）terpolymer microspheres（SMITMs）with tunable crosslinking degree were prepared by 2SP polymerization method.By varying the feeding amount of IP,the gel fraction of SMITMs could be regulated from 0 to 99%and the particle size changed from 623 to 1156 nm,respectively.Structural analysis demonstrated that the electron donors（St and IP）and electron acceptor（MAH）were copolymerized in an alternating way,while the IP participating in the polymerization by 1,4 addition.The rate of polymerization reaction was fast in the first 60 min,and the particle size of microspheres can increase from～400-500 nm to～900-1000 nm in 10-60 min,then the change tended to level off.The composition analysis showed that the content of MAH units in the SMITMs was 50 mol%in this polymerization system.The Diels-Alder（D-A）addition side reaction between IP and MAH during the polymerization process can be effectively suppressed by increasing the amount of initiator or decreasing the polymerization temperature.The SMITMs possessed good thermal stability with high initial decomposition temperature(T_5%>265℃)and maximum weight loss rate temperature（T_p>370℃）.The glass transition temperature（T_g）of the terpolymer decreased linearly from 210℃ to 90℃ with the increase of IP content.The hydrophilicity of the microspheres could be improved by converting the anhydride groups to amide acid groups through in situ gas-solid ammoniation reaction.SMITMs with different crosslinking degrees exhibited different dispersion behaviors in aqueous solution after ammonolysis,and the corresponding viscosity of dispersion solution decreased from 21.35 c P to 2.45 c P with increasing the crosslinking degree of SMITMs,providing a new strategy for the synthesis of crosslinked hydrophilic microspheres.2.Crosslinked porous microspheres（TMs）with a large number of reactive anhydride groups（62.5-71.8 mol%）,large specific surface area（51.6-182.4 m²/g）and mesoporous structure（average pore size:3.4-3.8 nm）were prepared based on the 2SP copolymerization of triallyl isocyanurate（TAIC）and MAH.Then the TMs were further functionalized with polyethylenimine（PEI）to give rise to a novel adsorbent（Cat-TMs）for efficient and rapid adsorption of diclofenac sodium（DS）in water.Due to a large number of adsorption sites（cation density:4.291 mmol/g）and unique pore structure,Cat-TMs showed excellent adsorption performance to DS with a very high equilibrium adsorption capacity up to 1421 mg/g and reached adsorption equilibrium within 30 min.The pseudo-second-order model and Langmuir model were a good fit for the adsorption kinetic and isotherm process,respectively,and the driving force of adsorption is electrostatic attraction.Cat-TMs can maintain a high adsorption capacity at p H 6-10,and realized the desorption of DS at a higher p H to achieve the reuse.The regenerated Cat-TMs maintained an adsorption rate of more than96%even after 5 adsorption-desorption cycles,and kept good stability in aqueous solutions with different p H and different types of organic solvents.3.A series of monodisperse copolymer microspheres（DDMs/TDMs）with raspberry-like structures were prepared based on the 2SP copolymerization of diethylene glycol divinyl ether/triethylene glycol divinyl ether（DEGDVE/TEGDVE）and MAH,and the self-assembly and modification of microspheres were used to construct hydrophobic surfaces with rough micro-nano structures.The effects of solvent（2-butanone/cyclohexane）ratio and monomer ratio on the morphology and composition of microspheres were investigated.With the increase of cyclohexane in the solvent,the particle size of the microspheres showed an increasing trend.The final composition of the microsphere was independent with the proportion of monomer ratio which showed a molar ratio of 1:2 for both the copolymerization of DEGDVE with MAH and TEGDVE with MAH,respectively.The arrays of DDMs and TDMs deposited on the glass surface have Debye diffraction phenomena that vary with the particle size,and the diameter of the diffraction ring decreases linearly with the increase of the particle size.The raspberry-like rough structure of DDMs and TDMs resulted in the surface roughness of glass up to 267 nm and 274 nm,respectively.The surface contact angle of glass can be increased from 37°to113°and 121°by in-situ conversion MAH groups in DDMs and TDMs to imide groups.