STRUCTURE OF WATER-CONTAINING LATEXES - REMAGNETIZATION EFFECTS DURING SOLID-STATE NMR SPIN-DIFFUSION EXPERIMENTS

Solid-state NMR H-1 spin diffusion experiments and transmission electr on microscopy are used to elucidate complex latex structures. Remagnet ization effects are detected in a three-component system with one rigi d and two different soft phases, which are discriminated by their H-1 chemical shift. The remagnetization effects facilitate the interpretat ion of spin-diffusion experiments for structure investigation of three -component structures. The investigated system consists of a polybutyl acrylate (PBuA)/polystyrene (PS)/poly(acrylic acid) (PAA) latex film c ontaining residual water, where the respective latex was synthesized b y a two-step emulsion polymerization. Transmission electron microscopy showed that the latex possesses an inverse core-shell-like structure, where the second step comonomer polymerizes inside the seed particle. A thin layer of water (3-5 nm) at the outside of the particles is det ected by NMR. Additionally, the NMR experiments show heterogeneities i n the core, where mobile regions 4 nm in diameter are found, much smal ler in size than the core itself, which has an average diameter of ca. 120 nm as measured by dynamic light scattering.