Particle morphology of carboxylated poly-(n-butyl acrylate)/poly(methyl methacrylate) composite latex particles investigated by TEM and NMR

Particles with a copolymer soft core of poly(n-butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) and a homopolymer hard shell of PMMA were characte rized using transmission electron microscopy and solid-state NMR spectrosco py. Two synthesis parameters were investigated: (1) the phase ratio of the core and the shell and (2) the compatibility of the two phases. A series of core-to-shell ratios from 100/0 to 25/75 were synthesized and characterize d. The compatibility between the phases was changed (1) by using acrylic ac id in either the core and the shell or in both, (2) by synthesizing a homop olymer or a copolymer core or (3) by introducing crosslinking points in the core. The combination of transmission electron microscopy and solid-state NMR spectroscopy allows quantitative determination of the extent of coverag e of the core by the shell polymer and the interphase thickness; both were found to depend on the shell content and the compatibility of the phases.