Heterogeneous Structures in the Synthesis of Hydrophobic Lauryl Acrylate-Styrene-Ethylene Glycol Dimethacrylate Copolymer Particles

Abstract

Novel crosslinked hydrophobic lauryl acrylate-styrene-ethylene glycol dimethacrylate copolymer particles were synthesized with heterogeneous structures by radical suspension copolymerization with benzoyl peroxide as the initiator. Ethylene glycol dimethacrylate was used as a crosslinking agent; toluene, cyclohexanol, 1-octanol and liquid paraffin were used as porogens. The effects of the crosslinking monomer and porogens on the morphologies of the copolymer microspheres were investigated. The copolymers were characterized by FTIR, SEM and swelling in toluene. Permanent pores remained in the dried polymeric particles prepared with nonsolvating porogens at certain crosslink densities as indicated by SEM pictures. The results of swelling revealed that 1-octanol was the most effective porogen, leading to the LA-S-EGDMA copolymer particles with maximum porosity and optimized spheric morphology. Furthermore, lower crosslink density and higher porogen contents promote the formation of porous morphology. INTRODUCTIONThe applications of methacrylic ester crosslinked polymers with permanently porous structures have attracted increasing attention all over the world. Exploitation occurs in areas a diverse as chromatography, polymer-supported catalysts, ion recovery [1], water treatment and purification [2][3][4][5]. For many applications it is important to utilize a porous resin with a high surface area. The formation conditions of porous (heterogeneous) structures in resin have been the subject of both applied and fundamental research for many years. As early as the end of the 1950s, Du s sek [6], Kunin [7,8], and Millar et al. [9][10][11] had already discovered this polymerization technique. According to the present reports [12][13][14][15][16][17][18][19][20][21][22][23][24], it was concluded that porous matrices can be obtained by suspension copolymerization, using monovinylic monomers and crosslinking reagents in the presence of inert porogens. These porogens may be extracted after polymerization, leaving holes or pores in the copolymer structures. Good solvents, nonsolvents, polymeric solvents, or mixtures of them may be used as porogens, leading to different kinds of pore size distributions.A variety of acrylic ester resins with different specific areas and porosity had been prepared by varying the type and ratio of porogen at a given condition [13,[25][26][27][28][29]. However, the preparation of perfusion particles was complicated, and this method was most used in trimethylolpropane trimethacrylate, 2-hydroxyethyl methacrylate, EGDMA, or methacrylate systems, and long alkyl chain acrylates systems have not been reported. Furthermore, the choice of polymerization conditions and experimental optimization must be specific for each chosen monomer system [20]. So it is necessary to further study.In our work, a novel hydrophobic porous copolymer, lauryl acrylatestyrene-ethylene glycol dimethacrylate copolymer, was prepared by the suspension polymerization technique in the presence of porogens. The effect of the independen...