Infrared spectroscopic studies of polystyrene emulsion polymers: Effect of oxidation during polymerization

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Abstract
Infrared spectroscopy was empolyed to study the nature of the structural changes which occurred through oxidation during the emulsion polymerization of styrene. Aliphatic carboxylic, amino, and phosphate emulsifiers and hydrogen peroxide and potassium persulfate initiators were empolyed for polymer preparation. In addition, a polystyrene dispersion prepared in the absence of any emulsifier or stabilizer was examined. Irrespective of the nature of the initiator–emulsifier combination employed, all of the polymer spectra revealed bands at 1705 and 1770 cm.−1. The band at 1705 cm.−1 was assigned in part to the carbonyl stretching mode of dimertic carboxylic acid, formed by oxidation, in the polystyrene chains. Absorption at 1770 cm.−1, which was very weak, was tentatively attributed to the carbonyl stretching mode of the monomeric form of this acid. The structure of the acid endgroup was not established, but the results obtained suggest that it was possibly a phenylacetic acid residue or a residue with a similar structure.
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