Synthesis and Microstructure Characterization of Dye-Labeled Poly(vinyl acetate-co-dibutyl maleate) Latex for Energy Transfer Experiments

We examined the emulsion copolymerization of vinyl acetate (VAc) with dibutyl maleate (DBM) (VAc:DBM 4:1 w/w) in the presence of three dyes chosen for fluorescence resonance energy transfer (ET) experiments. The donor dyes were 9-acryloxymethylphenanthrene (PheMA) and 9-methacryloxymethylphenanthrene (PheMMA), and the nonfluorescent acceptor dye was 2‘-acryloxy-4‘-methyl-4-( N, N -dimethylamino)benzophenone (NBen). The presence of the DBM comonomer significantly retards the rate of polymerization, which makes it hard to obtain monomer-starved feeding conditions for semicontinuous VAc−DBM emulsion polymerization. Under batch emulsion conditions, the polymer produced from the 4:1 wt ratio of VAc:DBM shows a composition by 1 H NMR throughout the polymerization that is very close to the monomer feed ratio. Other evidence, however, shows that there is microphase separation in the latex polymer. It appears that the nature of this phase separation remains constant as a function of monomer conversion. This copolymerization behavior allowed us to obtain dye-labeled latex particles with uniform dye labeling. In this way we synthesized latex particles with a diameter of ca. 100 nm containing 1 mol % PheMA or PheMMA and similar particles containing 0.3 mol % NBen. We report preliminary nonradiative energy transfer experiments on these latex films and on their solvent-cast counterparts. These experiments provide further information about phase separation in the films and also about the rates of polymer diffusion in these P(VAc- co -DBM) latex films. We compare results obtained in films in which PheMA is the donor dye with those in which PheMMA is the donor dye.