Preparation Of Hydrophilic Gigaporous Polystyrene Microspheres By RAFT Polymerization

With the rapid development of modern biotechnology,the application of protein becomes more and more extensive.However,most proteins exist in the form of mixture and need to be purified prior to using in the fields of life sciences and medicines.Liquid chromatography is the most effective tools for proteins separation.Recently,there are increasing interests in developing bioseparatioin media with high column efficiency,high column capacity,high-speed velocity and low activity loss.Considering the current situation of bioseparation media,we developed a novel method to prepare hydrophilic gigaporous polystyrene microspheres（HGPS）.Amphiphilic diblock glycopolymers（ADG）were firstly synthesized via reversible addition fragmentation chain transfer polymerization（RAFT）method.Taking ADG as oil phase surfactant,a bottom-up approach based on surfactant reverse micelles swelling method was proposed to prepare HGPS.After further derivatized as weak cation exchange medium.The dissertation was divided into three parts.In the first part,we successfully synthesized ADG by RAFT reaction.The proportion of hydrophilic and hydrophobic segments（HLB value）and molecular weights of ADG were controlled by adjusting RAFT reaction conditions.And then using ADG as oil surfactant,the critical micelle concentration（CMC value）of the ADG in the oil phase solution was measured by a surface tension meter.Inverted fluorescence microscope and conductivity method were used to characterize the process of ADG reverse micelles swelling and forming water channels in the solution,the double continuous structure of the emulsion and the maximum water absorption of the system,so as to provide basic conditions for ensuring the pore structure connectivity of the polymerized microspheres.In the second part,the HGPS microspheres were prepared by surfactant reverse micelles swelling method.We investigated several factors that have influence on the pore structure of microspheres:sodium lauryl sulfate and polyvinyl alcohol as mixed dispersants help to form super-large pores of microspheres;ADG with HLB value in the range of 3.6-4.5 could form ideal gigapores in the HGPS microspheres;the pore size of HGPS microspheres will increase with the molecular weight and concentration of ADG,which is in good accordance with the rule of water adsorption capacity of reverse micelles.In addition,the specific surface area of microspheres could be adjusted by addition of small molecular porogen.The HGPS microspheres with meso-and giga-pores can be successfully prepared via coordinated regulation of the HLB value,molecular weight and adding amount of ADG,as well as the addition of porogenic agent-toluene.Combined with the structure of W/S/O bicontinuous emulsion,the formation mechanism of gigaporous structure of HGPS microspheres was verified.Protein adsorption,the water contact angle and water content measuring experiments indicate the HGPS microspheres have good hydrophilicity and biocompatibility,resulting from the successful integration of ADG in the microspheres.Hydrodynamic experiment confirmed the good mechanical strength of microspheres,resulting from strong PS skeleton and the existence of through pores in the particles.The third part is to further derivatize the HGPS microspheres into a carboxymethylated weak cation exchange medium by etherification reaction.The three factors affecting the ion exchange capacity of the medium are the temperature,Na OH concentration and Cl CH₂COOH concentration.The important factors are the highest ligand density in the medium with Na OH concentration of 2.25 M,Cl CH₂COOH concentration of 0.529 M and 60℃ for 4h.