SP-PLP-EPR Investigations into the Chain-Length-Dependent Termination of Methyl Methacrylate Bulk Polymerization

Termination kinetics of methyl methacrylate (MMA) bulk. polymerization has been studied via the single pulsed laser polymerization-electron paramagnetic resonance method. MMA-d(8) has been investigated to enhance the signal-to-noise quality of microsecond time-resolved measurement of radical concentration. Chain-length-dependent termination rate coefficients of radicals of identical size k(t)(i,i), are reported for 5-70 degrees C and up to i = 100. k(t)(i,i) decreases according to the power-law expression k(t)(i,i) = k(t)(1,1).i(-alpha). At 5 degrees C, k(t) for two MMA radicals of chain-length unity is k(t)(1,1) = (5.8 +/- 1.3) . 10(8)L . mol(-1) . s(-1). The associated activation energy and power-law exponent are: E-A(k(t)(1,1)) approximate to 9 +/- 2 kJ . mol(-1) and alpha approximate to 0.63 +/- 0.15, respectively.