Abstract: The UVabsorption of α-hydroxy-α,α-dimethyl-(p-hydroxyethyloxy)-acetophenone(HMHOAP), α-hydroxy-α,α-dimethyl-acetophenone(HMAP) and α,α-dimethoxy-α-phenyl-acetophenone(DMAP) in different media was investigated. The apparent blue-shift of the peak position in O/W microemulsion compared to that in pure oil phase is an evidence of the location of the photoinitiator at the interfacial area. The locus of photoinitiator in microemulsion and its significance in understanding the initiation mechanism were discussed.

Key words: Microemulsion, Photoinitiator, UV absorption