Structure of water-containing latexes: Remagnetization effects during solid-state NMR spin-diffusion experiments

Abstract

Solid-state NMR 1H spin diffusion experiments and transmission electron microscopy are used to elucidate complex latex structures. Remagnetization effects are detected in a three-component system with one rigid and two different soft phases, which are discriminated by their 1H chemical shift. The remagnetization effects facilitate the interpretation of spin-diffusion experiments for structure investigation of three-component structures. The investigated system consists of a polybutylacrylate (PBuA)/polystyrene (PS)/poly(acrylic acid) (PAA) latex film containing residual water, where the respective latex was synthesized by 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 detected by NMR. Additionally, the NMR experiments show heterogeneities in the core, where mobile regions 4 nm in diameter are found, much smaller in size than the core itself, which has an average diameter of ca. 120 nm as measured by dynamic light scattering.