Synthesis of crosslinked (meth) acrylate spheresby SPG emulsification and their evaluation as solvent-absorbing material

Abstract

Crosslinked poly(meth)acrylate polymers with a variety of morphologies weresynthesized in two steps. In the first step, a microporous glass membrane (ShirasuPorous Glass, SPG) was employed to prepare uniform emulsion droplets by applyingadequate pressure to the monomer phase, which is composed of an initiator, solvent,and a mixture of monomers. The droplets were formed continuously through the membraneand suspended in the aqueous solution, which contains a suspending agent, anemulsifier and an inhibitor to suppress the nucleation of secondary particles. TheSPG pore sizes of 0.90, 5.25 and 9.25 (+,m)m were used. Then, the emulsion dropletswere polymerized at 70(+,ฐ)C with the rotation rate 160 rpm for 24 h. The(meth)acrylate monomers, such as, 2-ethylhexyl acrylate (2-EHA), 2-ethylhexylmethacrylate (2-EHMA), cyclohexyl acrylate, methyl methacrylale (MMA), laurylacrylate (LA) and lauryl methacrylate (LMA) were used in this research. Theinfluences of the ratios of monomer and crosslinking agent, ethylene glycoldimethacrylate (EGDMA), the amount of diluents (toluene and heptane), the monomertypes and the diluent/solvent types on the polymer particle morphology, the swellingdegree and the polymer particle sizes were investigated. We found that an increase inthe concentration of ethyleneglycol dimethacrylate and heptane resulted in highercoarse porous spheres and smaller polymer particle size. A coefficient of variationclose to 10% was obtained. The capacity of these spheres as solvent absorptionmaterials was examined. The highest swelling degrees of heptane and toluene wereobtained when lautyl acrylate was employed as a monomer with 30% (by weight) ofethyleneglycol dimethacrylate and 70% (by weight) of heptane as an inert solvent. Thehighest capacity of solvent absorption was obtained when 4.81 (+,m)m of the polymerparticle sizes prepared by the SPG pore size 0.9 (+,m)m was used. The polymerparticles were able to absorb aliphatic hydrocarbon solvents, aromatic hydrocarbonsolvents and the mixed solvents between the aliphatic hydrocarbon solvent and thearomatic hydrocarbon solvent, such as toluene and heptane. The capacity of thesolvent absorption in the aromatic hydrocarbon solvents was higher than the aliphatichydrocarbon solvents. Besides, the particles did not rupture or collapse after theabsorption in solvents.