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 °C and up to i  = 100. k   t i , idecreases according to the power‐law expression $k_{\rm t}^{i,i} = k_{\rm t}^{{\rm 1,1}} \cdot i^{ - \alpha }$ . At 5 °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 ) ≈ 9 ± 2 kJ · mol −1 and α  ≈ 0.63 ± 0.15, respectively.