Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

Abstract

High resolution scanning soft X-ray transmission microscopy (STXM) has been employed to investigate individual thermoresponsive microgel particles in aqueous environments. STXM generates 2-dimensional projections with spatial resolutions in the regime of a few 10 s of nm. In the present study we are able to regain a 3D representation of the investigated specimen and observe the deswelling of the microgel particles upon heating, thus offering insight into the thermoresponsive behaviour of individual differently sized particles. We employ a 2-shell model that is able to derive the radial concentration profile of individual microgels particles and thus serves as a complementary method to scattering experiments that average over all particles. Furthermore, we are able to detect the different deswelling behaviour of the particle interior and its interface to the water environment.

Interfacial Engineering of Thermoresponsive Microgel Capsules: Polymeric Wetting vs Colloidal Adhesion

“…To describe the excluded volume effect between particles, LJ (12–6) potential with a cutoff distance of is adopted, which corresponds to purely repulsive interactions. , Besides, the Morse potential with a cutoff of r m = 1.25σ is introduced to describe the short-range attractive interactions. , By combining the short-range LJ (12–6) and Morse potentials, the thermal properties of polymer systems can be mimicked properly. − Moreover, previous studies have demonstrated that this combination exhibited good agreements with experimental observations in the aspects of thermodynamic and dynamical properties of polymers. − Importantly, these dynamical models and parameters are verified by our previous study and show good agreements with experimental observations. ,, Different cutoffs are adopted in potential equations; thereby, they will result in some weak discontinuities in the energy and/or infinite forces. In this case, precise autocorrelation functions for a thermostat are needed to avoid collective density oscillations for the polymer monomers and to damp out the oscillatory motions .…”

Recent Advances in Microgels: From Biomolecules to Functionality

“…[302] The thermosensitive radial profiles of microgels in aqueous environments can be obtained in a scanning soft X-ray transmission microscopy, and the deswelling of the microgels can be analyzed digitally. [303] Small-angle X-ray scattering (SAXS) can be used to determine the shape and the structural transition of biological molecules, [304,305] and the structural evolution during microgel-to-particle collapse indicate there is a hollow structure in between. As a complement of SAXS, small angle neutron scattering (SANS) can also function as a simple way to employ contrast variation for unique information in microgel studies.…”

Three-dimensional focal stack imaging in scanning transmission X-ray microscopy with an improved reconstruction algorithm

“…Scanning transmission X-ray microscopy (STXM) is capable of acquiring 2D nanoscale images based on density, elemental or spectroscopic contrast. Several approaches have been developed to extend STXM to 3D, such as nanotomography, 3D ptychography, confocal microscopy and radial profile analysis [15][16][17][18][19][20]. Tomography is currently the primary technique used to reconstruct 3D images of materials and biological specimens in STXM, recently achieving a spatial resolution of 11 nm in combination with ptychography [21].…”