Dynamic light‐scattering study of an ethylene–methacrylic acid copolymer and its salt

Dynamic light‐scattering experiments were performed on an ethylene–methacrylic acid copolymer and its sodium salt. The in‐phase Δ I ′ and out‐of‐phase Δ I ″ components of the light scattering were measured in a temperature range between 25 and 65°C for both samples. No transition is seen in this temperature interval for the acid, but a clear transition occurs around 40°C for the salt. This transition is associated with the softening point of the ionic domains present in the sample.