Abstract: Using 2-bromo-(2-methyl-1-oxopropoxy)-2-methyl-propio-phenone(HMPP-Br) as a photoinitiator, the controlled/living photopolymerization of n-butyl methacrylate(n-BMA) mediated by 2,2,6,6-tetramethyl-piperidinyl-l-oxyl(TEMPO) and 2,2,6,6-tetramethyl-4-piperidinol(TMP) in the microemulsion of n-BMA/n-butanol/SDS-H₂O system (O/W) was performed at ambient temperature.The controlling mechanism and reaction kinetics of controlled/living free radical photopolymerization of n-BMA in microemulsion was investigated. It was shown that the monomer conversion increased linearly with the increased exposure time, and the number-average molecular weight (M_n) of Poly(n-BMA) is increased linearly with the monomer conversion increasing under the condition with[TEMPO+TMP]/[HMPP-Br]=1.1, the content of initiator of 4.5%(mass fraction) and the irradiation intensity of 5.5 mW/cm². The results show that when it was mediated by TEMPO/TMP, the photopolymerization of n-BMA in the microemulsion was to be kineticly controlled. It was found that the plots of number-average molecular weight vs. conversion and ln([M]₀/[M]) vs. time were liner respectively, and the n-BMA homopolymers exhibited relatively narrow molecular weight distributions (PDI=1.25—1.45), even until the conversion was up. This shows that TEMPO combined with TMP used as a mediator was evidently available.

Key words: n-butyl methacrylate, O/W microemulsion, controlled/living photopolymerization, 2,2,6,6-tetramethyl-4-piperidinol, 2,2,6,6-tetramethyl-piperidinyl-l-oxyl(TEMPO), reaction kinetic