In situ characterization of crystallization and melting of soft, thermoresponsive microgels by small-angle X-ray scattering

Abstract

Depending on the volume fraction and interparticle interactions, colloidal suspensions can form different phases, ranging from fluids, crystals, and glasses to gels. For soft microgels that are made from thermoresponsive...

SAXS Investigation of Core–Shell Microgels with High Scattering Contrast Cores: Access to Structure Factor and Volume Fraction

“…6,29,59 This is also in good agreement with our previous results. 21,40 Also, the radius of gyration Rg = 71.1 ± 1.7 nm determined from Guinier analysis is smaller than Rs (see Figure S6 and discussion in the Supporting Information).This can also be ascribed to the gradient in cross-linker density. A similar difference is found when we compare Rg and Rh where we find the ratio Rg/Rh = 0.68, which is typically observed for microgels, for example studied by light scattering.…”

“…26,69 Here we also want to mention the work of Lapkin et al where a similar system was investigated with larger focus on the crystal structures. 21 In Figure 4a, upon increasing ϕcs all peaks move to higher q values indicating a decrease in lattice constant. In addition, the intensity of the structure factor peaks decreases for increasing ϕcs which we attribute to a decrease in the degree of order.…”

“…While the small gold nanoparticle cores dominate the mid to high q scattering in SAXS, they do not significantly affect the inter-particle interactions that are governed by the microgel shells. The short acquisition times of SAXS open up the possibility to investigate the impact of temperature changes on the microgels in dense packing, which induces melting and recrystallisation of the system, due to the temperature-dependent volume of the microgels 21 , but has also been shown to change the particle interactions. 72 In addition, core-shell microgels with high contrast cores will allow further explorations of other fundamental phenomena such as jamming and the glass transition of soft colloidal systems.…”

Fluid interface-assisted assembly of soft microgels: recent developments for structures beyond hexagonal packing

“…27,28 When microgels are composed of polymers that feature a lower critical solution temperature (LCST), with poly-Nisopropylacrylamide (PNIPAM) being the most widely known and studied example, 3 their volume can be changed simply by changing temperature. 29 This volume phase transition (VPT) behavior renders PNIPAM microgels as such an interesting system for fundamental research, for example to study phase transitions in dense packings, where the microgel volume fraction can be altered by temperature, 30 but also for applications in the field of sensing, drug delivery and as cell culture media. [31][32][33][34] PNIPAM microgels are typically synthesized via free radical precipitation polymerization leading to spherical microgels of low polydispersity.…”

Crystallization kinetics of charged PNIPAM microgels dispersions at low volume fractions

“…Moreover, the possibility of controlling the particle pairinteraction in colloids makes them very attractive. In particular, the peculiarity of microgel systems allows for tuning the particle interaction potential by changing the temperature and, consequently, inducing crystallization in a controlled way [14,15]. This characteristic may be of great interest in material science to design, for example, photonic materials made of thermosensitive microgels [5, [16][17][18].…”