Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Abstract

Monodisperse polar gradient particles were synthesized via a three-step emulsion polymerization using poly(butyl acrylate-methyl methacrylate-methacrylic acid-ethylene glycol dimethacrylate) (P(BA-MMA-MAA-EGDMA)) as core, poly(methyl methacrylate-methacrylic acid-styrene) (P(St-MMA-MAA)) as interlayer and polystyrene (PSt) as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two-layer core/interlayer and three-layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl-containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage.

Sequence Distribution and Cumulative Composition of Gradient Latex Particles Synthesized by a Power-Feed Technique

“…Various techniques have already been explored to precisely control these chain tailor-made structures, − including both innovative polymerization method, such as nitroxide mediated polymerization (NMP), , atom transfer radical polymerization (ATRP), − reversible addition–fragmentation chain transfer polymerization (RAFT), − and single-electron transfer and single-electron transfer degenerative chain transfer living radical polymerization. , More recently, the combination of controlled/living radical copolymerization (CLRcoP) with a specific polymerization program has been widely utilized to achieve that purpose and the synthesized copolymer structures are now theoretically and practically fine-tuned by combining ATRP or RAFT with the appropriate polymerization program. − Since its particular “living” intrinsic of CLRcoP, the synthesized polymer chain, without chain transfer and termination, would be subject to a gradient structure in a series of identical polymer chains. However, the widely used transition-metal catalysts limit the application in polymers, since catalysts are expensive and hard to remove from the polymers, resulting in changes in electronic and mechanical properties of final polymer product, as well as their color.…”

Influence of unsaturated acid monomer on the morphology of latex particles in the preparation of hollow latex via the alkali post‐treatment

“…Therefore, it is necessary to further understand the mechanism lies in the morphological evolution of the latex particles, though there are some researches about void latex particles have been reported. Recently, we have been engaged in the preparation of hollow polymer latex and the control of particle morphology from synthesizing multistage hydrophilic core/hydrophobic shell latex particles and performing alkali post‐treatment based on the osmotic swelling principle, and some valuable results were obtained 27–29. In this article, with the aim of further understanding, the mechanism behind the formation of hollow morphology from aspect of unsaturated acid monomer, three‐layer core/shell latex particles with hydrophilic core and hydrophobic shell were designed, and an interlayer with moderate polarity was inserted into the core and the shell to make the encapsulation of the hydrophilic core with the hydrophobic shell more effectively.…”