ABSTRACT
We introduce a general and relatively straightforward protocol aimed at determining the absolute photoinduced radical generation efficiency via NMR monitoring. This approach relies on the use of a radical scavenger probe that combines a nitroxide moiety that specifically reacts with radicals and a trifluoromethyl group used as a 19F NMR signaling unit. Using an LED source, whose fluence is precisely determined by a chemical actinometry procedure also described herein, the method is used to determine the radical photogeneration quantum yields of three well-known polymerization initiators: azobisisobutyronitrile (AIBN), 4,4'-bis(N,N-diethylamino)benzophenone (BDEBP, a derivative of Michler's ethyl ketone), and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (MAPO). The overall good agreement with values previously reported in the literature proves the robustness of this new method. We then extended the study to the precise measurement of the quantum yield of free-radical photogeneration on a newly synthesized photoinitiator used for two-photon direct laser writing. This study highlights the potential of this methodology for the quantitative determination of photoinduced radical generation efficiency used in many fields of applications.
ABSTRACT
Preparation of degradable materials using reversible deactivation radical polymerizations (RDRP) is of particular interest for biomedical applications. In this paper we report preparation of degradable copolymers of 2-methylene-4-phenyl-1, 3-dioxolane (MPDL), monomer which undergoes ring-opening reaction and forms ester bond upon radical polymerization, with hydrophobic and hydrophilic methacrylate monomers using atom transfer radical polymerization (ATRP). Copolymers composition and degradation were evaluated upon varied temperature and monomer type.
