Visible Light Induced Emulsion Polymerization: An Improved Photoinitiation System Based on Amphiphilic Tertiary Amine N-Oxides

A new method for visible-induced emulsion polymerization is successfully demonstrated. Photoinitiators are used upon irradiation with visible light to undergo sequential photodecomposition, demonstrating an effective way to generate radicals with octadecylamine ethoxylates N-oxide (AO-1805, EO = 5). AO-1805, acting both as a surfactant and mediator simultaneously, is proposed for free radical generation through synergistic effects with the photoinitiator, which differs greatly from organoboron compounds, especially in emulsions. Comparative experiments are carried out with nonylphenol ethoxylates (NP-10, EO = 5) upon irradiation with UV and visible light in order to examine the nature of the photoinitiated emulsion polymerization with AO-1805. The laser flash photolysis method is then used to study the interaction between AO-1805 and free radicals. The emulsion photopolymerization of styrene may be successfully mediated by AO-1805, with good control over molecular weight. A synergistic effect between radicals and AO-1805 is observed in the UV irradiation process that can further mediate radical polymerization. In visible light-induced emulsion polymerization, AO-1805 also has a novel stabilizing role because of the interaction between D1 and AO-1805. Moreover, it is hard to see such a trend with the NP-10/D1 combination, indicating that the functional group (N-oxide) of AO-1805 plays an important role in photoinitiation and has an influence on the overall polymerization rate.