Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant

Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant (N,NN,N-dimethyl-N-nN-n-dodecyl-N-2-methacryloyloxyethylammonium bromide:C12Br) and a cationic initiator (2,2′-azobis(2-amidinopropane) dihydrochloride:V50), called St/C12Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C12Br/AIBN, where an oil-soluble initiator, i.e., 2,2′-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C12Br/V50 compared to pyrene (Py) in St/Py/C12Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C12Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C12Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution.

Highly monodisperse fluorescent polymer particles containing pyrene fluorophores were prepared by miniemulsion polymerization of styrene with a polymerizable surfactant.Figure optionsDownload as PowerPoint slide