Characterization of the microstructure of latexes by thermally stimulated currents

The microstructure of latexes has been investigated by differential scanning calorimetry (DSC) and thermally stimulated currents (TSC). The copolymers were prepared by emulsion copolymerization of acetate (A). Three series of samples were obtained: an SC copolymer, obtained by semicontinuous feeding with A and S; and ASS and SAS copolymers, both obtained by step feeding with A and S, but in different order. The SC copolymer is characterized by a narrow glass transition and a single-TSC peak. Analysis of the fine structure of the peak shows that it is associated with a single compensation law. This behavior is typical for a statistical copolymer. On the other hand, copolymers prepared by step feeding have a broad glass transition and two TSC peaks. This behavior is characteristic of block copolymers. This result is confirmed by the existence of two compensation laws, indicating a biphasic structure. The SAS copolymer has been found to have a higher segregation than ASS, probably because of higher reactivity of styrene and its hydrophobicity