Aqueous microgels modified by wedge-shaped amphiphilic molecules: hydrophilic microcontainers with hydrophobic nanodomains

Hydrophobic Monomers Recognize Microenvironments in Hydrogel Microspheres during Free-Radical-Seeded Emulsion Polymerization

The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications.

Aqueous microgels modified with photosensitive wedge-shaped amphiphilic molecules: synthesis, structure and photochemical behaviour

Aqueous microgels based on poly(N-vinylcaprolactam) with reversible temperature-induced volume transition are promising "smart" materials for various applications. In this work, the microgels are modified via acid-base interaction by wedge-shaped amphiphilic sulfonic acid molecules with alkyl chains of different lengths and an azobenzene group. In contrast to the pristine microgel the modified microgels retain colloidal stability in water and show different responses to the change of temperature and pH. The azobenzene group in the ligand molecules acts as a spectroscopic and kinetic probe sensing the microenvironment inside the microgel particles. Thus, the observed hyperchromicity upon heating suggests the enhancement of hydrophobicity with the increase of temperature. The hydrophobicity of the microgel interior increases with the increase of the modification degree as indicated by the increase of activation energy of the thermal Z/E isomerization of the azobenzene group.

A versatile synthetic platform for amphiphilic nanogels with tunable hydrophobicity

Functionalization of reactive precursor particles allows the preparation of amphiphilic nanogel libraries with tunable network hydrophobicity and comparable colloidal features.

Polyacid microgels with adaptive hydrophobic pockets and ampholytic character: synthesis, solution properties and insights into internal nanostructure by cryogenic-TEM

Microgels with internal and reconfigurable complex nanostructure are emerging as possible adaptive particles, yet they remain challenging to design synthetically. Here, we report the synthesis of highly charged poly(methacrylic acid) (PMAA) microgels incorporating permanent (poly(methyl methacrylate) (PMMA)) and switchable hydrophobic pockets (poly(N,N'-diethylaminoethyl methacrylate) (PDEAEMA)) via emulsion polymerization. We demonstrate detailed tuning of the size, crosslinking density and tailored incorporation of functional comonomers into the polyacid microgels. Analysis via cryo-TEM and pyrene probe measurements reveal switchable hydrophobic pockets inside the microgels as a function of pH. The particles show a rich diversity of internal phase-segregation, that adapts to the surrounding conditions. Large amounts of hydrophobic pockets even lead to hydrophobic bridging between particles. The study shows ways towards tailored polyelectrolyte microgels with narrow dispersity, high charge density, as well as tailored and reconfigurable hydrophobic compartments and interactions.