Poly(isobutyl methacrylate) (PiBMA) microspheres with different crosslinking densities were synthesized by suspension polymerization technique in aqueous medium and their characterization and swelling behaviors in different solvents were investigated. PiBMA spheres with a 800- to 1500-mum-diameter range were obtained by using benzoyl peroxide (BPO) as polymerization initiator, 1/5 ratio of monomer/water in volume, tricalcium phosphate (TCP), and poly(N vinyl-2-pyrrolidone) (PVP) as suspension stabilizer with 350 rpm stirring rate in nitrogen atmosphere. The influence of type and amount of crosslinking agent on the swelling properties and diffusional behavior, diffusion coefficient, and network properties of the spheres were examined in pentane, hexane, heptane, and gasoline. Dynamic swelling behaviors of crosslinked spheres were determined by measuring the diameter of the sphere as a function of time by an optical microscope. Swelling behaviors and network properties were found to be dependent on the diameter, crosslinking density of the sphere, and crosslinking agent and solvent. The results of this study indicate that the crosslinked PiBMA microsphere can be swollen in gasoline very well and retains a high ratio (1500% of its volume) of gasoline in their structure. (C) 2002 John Wiley & Sons, Inc.