Macromonomers are convenient means for introducing a functional group to a produced polymer. Amphiphilic polymer particles having a 2-[p-(1,1,3,3-tetramethyl-butyl) phenoxy-polyethoxy] ethyl group are a good support of an immobilized enzyme for use in enzymatic reactions in an organic solvent. To synthesize the amphiphilic polymer particle, an amphiphilic methacrylic monomer (MAX-n) having a 2-[p-(1,1,3,3-tetramethyl-butyl) phenoxy-polyethoxy] ethyl group has been synthesized and polymerized. The radical polymerization kinetics of MAX-n in solution polymerization and seed polymerization were then studied. In solution copolymerization of styrene and MAX-n, when the number n of the ethylene oxide units is high, the steric hindrance of the side chain of MAX-n results in a low propagation rate constant and a high monomer reactivity ratio. In seed polymerization, using the kinetic parameter obtained in solution polymerization and the experimentally measured value of mass fraction of polymer at which the glass transition occurred, the time course of conversion of the seed copolymerization of MAX-n and styrene were simulated.