The effect of LiClO4 on the polymerization of di-2-[2-(2-methoxyethoxy)ethoxy]ethyl itaconate (DMEI) with dimethyl 2,2’-azobisisobutyrate (MAIB) was investigated in methyl ethyl ketone (MEK) kinetically and by ESR. The polymerization rate (R(p)) at 50 degrees C, where the concentrations of DMEI and MAIB were 1.00 and 5.00 x 10(-2) mol/L, increased with increasing [LiClO4]. Marked acceleration was observed at higher [LiClO4]s than 1.0 mol/L. The molecular weight of resulting polymer (ca. 10,000) was relatively insensitive to [LiClO4], indicating occurrence of chain transfer. IR analysis of mixtures of LiClO4/DMEI and LiClO4/poly(DMEI) indicated complexation of LiClO4 with DMEI and its polymer. The rate constants of propagation (k(p)) and termination (k(t)) were determined by ESR. k(p) (1.7-10.5 L/mol s at 50 degrees C) increased with [LiClO4]. k(t) (5.2-1.0 x 10(4) L/mol s at 50 degrees C) showed remarkable decrease at higher [LiClO4]s than 1.0 mol/L. R(p) of polymerization of equimolar complex of LiClO4/DMEI with MAIB at 50 degrees C in MEK was expressed by R(p) = k[MAIB](0.5)[DMEI](2.4). k(p) increased and k(t) decreased with [DMEI]. The activation energies of overall polymerization, propagation and termination were estimated to be 34.5, 8.0, and 59.4 kJ/mol. Copolymerization of DMEI with styrene was also profoundly affected by the presence of LiClO4. Such large effects of LiClO4 on the homo- and copolymerization of DMEI are explicable in term of association of LiClO4-complexed DMEI monomers.