Structure formation of PNIPAM microgels in foams and foam films

Abstract

Responsive aqueous foams are very interesting from a fundamental point of view and for various applications like foam flooding or foam flotation. In this study thermoresponsive microgels (MGs) made from...

Influence of Dopamine Methacrylamide on Swelling Behavior and Nanomechanical Properties of PNIPAM Microgels

“…According to the Flory− Rehner theory, the E modulus of the microgels is linearly correlated with β, which was experimentally proven. 42 For pure PNIPAM microgels, a linear dependency is confirmed with increasing cross-linker BIS amount, including data obtained from Kuḧnhammer et al 42 for pure PNIPAM microgels without DMA. a P(NIPAM-co-DMA) microgels with an increasing amount of DMA (from MG C2,D0 compared to MG C2,D10 ) show the same linear trend in agreement with data for pure PNIPAM microgels and fall on the same m curve.…”

“…The affine network factor β, calculated as described in Section A by eq , is shown in dependency of the microgel’s E moduli in Figure . According to the Flory–Rehner theory, the E modulus of the microgels is linearly correlated with β, which was experimentally proven …”

“…The elastic modulus E was determined by fitting the approach part of the force curves with the Hertz model F = 4 E R 2 3 ( 1 − ν 2 ) δ 3 / 2 where F is the force of the indenter with radius R , ν is the Poisson ratio of the sample, δ is the indentation depth, and E is the elastic modulus. The fit region of the Hertz model was set to 0–40% of the maximum indentation depth δ to exclude the impact of the underlying surface on the resulting moduli. ,, The Poisson ratio ν for microgels varies from 0.25 to 0.5 in the literature. − For further analysis, a Poisson ratio of ν = 0.4 was used, which is close to the Poisson ratio of incompressible fluids in accordance with the literature for PNIPAM microgels. Under- or overestimating the Poisson ratio by ±0.15 leads to errors of 11.6% for the elastic modulus E .…”

Influence of Architecture on the Interfacial Properties of Polymers: Linear Chains, Stars, and Microgels

“…Microgels can be surface-active, effective, and responsive emulsifiers, foaming agents and coatings. ,,,− They have an eminent polymer–particle duality in both bulk solution and at interfaces. − As emulsifiers, they have barrier-free adsorption like polymers but also similarities to Pickering emulsions, such as superior stability due to their strong anchoring. , The on-demand breaking of emulsions stabilized with pNIPAM microgels described in the literature is of great interest for applications. ,,, This duality can be readily adjusted to either side by the cross-linking density and architecture of the microgels. ,,− For example, for ULC microgels, an interfacial concentration-dependent transition from a polymer-like to a particle-like film is observed …”

Stability and Structural Analysis Using Small-Angle Neutron Scattering for Foam of Homogeneous Polyoxyethylene-Type Nonionic Surfactants with Multibranched Chains

“…However, few studies have directly investigated the microstructure of foams. In recent years, small-angle neutron scattering (SANS) has been used as a direct method to study the microstructure of these foams. − Many setups are under development in SANS facilities, and the variety of methods for processing the neutron scattering data has recently surged. These methods enable broad descriptions to be provided at different length scales of foam using SANS.…”