Layer-by-layer synthesis of multilayer core-shell latex and the film formation properties

Polymer latex particles were synthesized with multilayer core-shell structure via surface cross-linking emulsion polymerization. The latex core is coated with a five-layer shell. The polymerization was done in a semicontinuous fashion monitored by a dynamic laser scattering (DLS). The copolymer in each layer is designed with alternating high and low glass transition temperature (T(g)). Divinylbenzene (DVB) was added as the cross-linking agent in the synthesis of the "hard" layers to prevent the molecular diffusion from the adjacent "soft" layers. The layer-by-layer increment on the latex core is proved by the alternating changes on the film-formation capabilities of different latex emulsions at room temperature in correspondence with the variance in the T(g) of the outermost polymer layer. The detailed morphologies of the films formed by the latex with different number of layers were characterized by atom force microscopy (AFM). The deformation of the latex particles is largely depended on the nature of the polymer in the outermost layer of the latex particles. Further characterization carried out by multifrequency temperature-modulated differential scanning calorimetry (TOPEM-DSC) confirmed the layer-by-layer structure of the particles, although the molecular redistribution and the interlayer structures were observed. The work provides a routine toward the synthesis of multilayer polymer latexes.