Did you know that differential scanning calorimetry (DSC) can be an important, even critical, analytical tool for determining the morphology of composite latex particles? Those who are responsible for providing reliable analyses for establishing the phase structure of composite particles know that complete characterization is quite challenging, sometimes complicated, and often lacking for suitable methods. To be complete, one needs to establish 1.) the degree to which the two polymers are physically separated within the particle; 2.) the amount of interfacial polymer between the separated phases; 3.) the relative locations of each polymer in the particle; and 4.) the polymer composition at the periphery of the particle (i.e. at its water interface).
TEM (and sometimes AFM) can be very helpful for #3 above – but it is not generally a quantitative analysis and is dependent upon one’s ability to selectively stain the polymers for contrast in the electron beam. Sample preparation and correctly focusing the beam can be challenging and potentially lead to errors of interpretation. Surfactant titration can be useful in determining the polymer composition at the particle surface. Acid comonomers can complicate such measurements, but one can turn to acid titrations with base to determine the amount of acid copolymer in the external region of the particle, but not necessarily that at the very surface of the particle where the surfactants adsorb.