Comparison of the synthesis of acrylate core/shell beads by seeded suspension polymerization and one stage polymerization

Abstract

Synthesis of solvent absorption-desorption core/shell beads was performed in the presence of benzoyl peroxide and poly (vinyl pyrrolidone) K-90 as an initiator and a suspending agent, respectively. The effects of reaction parameters, that are the initiator concentration, polymerization temperature, agitation rate, polymerization time, crosslinking agent concentration, concentration of suspending agent and diluent composition on the average particle size, size distribution and swelling properties of the resulting core/shell beads were investigated. The average particle size and size distribution was measured by sieve analysis, the swelling properties by gravimetric measurement, thermal property by DSC, kinetics of absorption and desorption by optical microscopy and surface morphology by SEM. The optimum condition for the synthesis of the core/shell bead of poly (methyl methacrylate)/polystyrene by one-stage suspension polymerization was found as follows: the amount of EGDMA was 7.0%; the toluene: i-octane ratio was 70:30; the polymerization temperature and time were 75℃ and 10hr, respectively. The poly (methyl methacrylate)/polystyrene was spherical beads and of core/shell morphology. The polystyrene was the core and poly (methyl methacrylate) was the shell. The properties of the beads are as follows: the average particle sizes in the range of 0.42-0.59 mm; the swelling ratio of 6.6 times in toluene and the diffusion coefficient in toluene: i-octane solvent in the range 0.1242-0.1743 of mm²min⁻¹ There are two steps of the synthesis of the seeded suspension polymerization. The first step is preparation of the seed particles; the other step is the polymerization of the styrene monomer for a formation of the shell layer on the seed particle. The optimum condition for the synthesis of the core/shell bead of poly (methyl acrylate)/polystyrene was found as follows: the amount of EGDMA was 15.0%; the toluene:i-octane ratio was 80:20; the polymerization temperature and time were 75℃ and 10hr, respectively. The poly (methyl acrylate)/polystyrene beads had the core/shell morphology. The core was poly (methyl acrylate) and the shell was polystyrene. The properties beads were as follows: the average particle sizes of 1.61 mm; the swelling ratio of 2.5 times in toluene and the diffusion coefficient in toluene: i-octane solvent in the range of 0.0711-0.0777 mm²min⁻¹ . The optimum condition for the synthesis of the core/shell bead of poly (2-ethylhexyl acrylate)/polystyrene was found as follows: the amount of EGDMA was 7.0%; the toluene: i-octane ratio was 60:40; the polymerization temperature and time were 75℃ and 10 hr, respectively. The poly (2-ethylhexyl acrylate)/polystyrene beads had a heterogeneous structure with opaque appearance. The bead had a core/shell morphology; the core was poly (2- ethylhexyl acrylate) and the shell was polystyrene. The properties of the beads were as follows: the average particle sizes of 0.4 mm; the swelling ratio of 3.0 times in toluene and the diffusion coefficient in toluene: i-octane solvent 0.7614 mm²min⁻¹. In the one-stage suspension polymerization, the polymer beads had a homogeneous structure, while the polymer beads from the seeded suspension polymerization had a heterogeneous structure with a distinct shell separated from the core of the respective polymers.