Poly(n-octyl methacrylate) viscosity index improver: Kinetic study via on-line super(1)H-NMR technique

The free radical solution polymerization of n-octyl methacrylate has been studied in benzene-d sub(6) in the presence of 2,2'-azobisisobutyronitrile as thermal initiator. An on-line nuclear magnetic resonance spectroscopy was applied to record the reaction data and to determine the monomer conversion at different times during the polymerization reaction. Effect of monomer and initiator concentration as well as reaction temperature on polymerization rate was studied. The order of the reaction with respect to initiator (0.45) was consistent with the classical kinetic rate equation, while the order of reaction with respect to monomer (1.87) was much greater than unity. An overall activation energy (E sub(a) = 53.8 kJ/mol) was obtained over the temperature range 328-338 K. Also, the efficiency of the synthesized poly(n-octyl methacrylate) for improving the viscosity index of the lube oil was investigated.