Anisotropic Hollow Microgels That Can Adapt Their Size, Shape, and Softness

Nickel, Anne C.; Scotti, Andrea; Houston, Judith E.; Ito, Thiago Heiji; Crassous, Jérôme J.; Pedersen, Jan Skov; Richtering, Walter

doi:10.1021/acs.nanolett.9b03507

Cited by 48 publications

(56 citation statements)

References 67 publications

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“…This is most likely related to the cavity. The latter gives the polymeric network an additional possibility to swell: not only toward the outer, but also toward the inner periphery [19,20,43]. The swelling ratio of Q(Hollow)= 2.00 ± 0.06 agrees with previous studies on hollow pure pNIPAM microgels with a cross-linking density of 5 mol% [42].…”

Section: Resultssupporting

confidence: 88%

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Synthesis and structure of temperature-sensitive nanocapsules

et al. 2020

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The transport and systematic release of functional agents at specific areas are key challenges in various application fields. These make the development of micro-and nanocapsules, which allow for uptake, storage, and triggered release, of high interest. Hollow thermoresponsive microgels, cross-linked polymer networks with a solvent-filled cavity in their center, are promising candidates as triggerable nanocapsules, as they can adapt their size and shape to the environment. Their shell permeability can be controlled by temperature, while the cavity can serve as a storage place for guest species. Here, we present the synthesis and structural characterization of temperature-responsive microgels, which are deswollen at room temperature and swell upon moderate cooling, to facilitate potential encapsulation experiments. We present microgels made from poly(N-isopropylacrylamide-co-diacetone acrylamide), p(NIPAM-co-DAAM), possessing a volume phase transition temperature below room temperature. Their colloidal stability in the deswollen state can be enhanced by adding a swollen polymer shell made of poly(N-isopropylacrylamide), pNIPAM, as periphery. The synthesis of hollow double-shell microgels comprising a cavity surrounded by an inner p(NIPAM-co-DAAM) shell and an outer pNIPAM shell is established. The inner network enables the control of the shell permeability: the network is deswollen at room temperature and swells upon moderate cooling. The outer network guarantees for steric stability at room temperature. Light scattering techniques are employed for the characterization of the microgels. Form factor analysis reveals that the cavity of the nanocapsules persists at all swelling states, making it an ideal site for the storage of guest species.

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Section: Resultssupporting

confidence: 88%

“…An intact cavity is crucial for storage applications. Its size can be tuned by the choice of the sacrificial core [22,42,43], the composition of the polymer shell [19,20], and the environmental constraints as adsorbed to interfaces [44][45][46] or entrapped in highly crowded solutions [42,47].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structure of temperature-sensitive nanocapsules

et al. 2020

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“…Similar considerations should be extended to microgels in bulk conditions, for which high-density states still require appropriate theoretical assessment. The analysis can be further broadened to other microgel topologies that have recently gained considerable attention, such as hollow [88], ultra-low-cross-linked [28], or anisotropic ones [89].…”

Section: Discussionmentioning

confidence: 99%

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

et al. 2020

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Soft colloids are increasingly used as model systems to address fundamental issues such as crystallization and the glass and jamming transitions. Among the available classes of soft colloids, microgels are emerging as the gold standard. Since their great internal complexity makes their theoretical characterization very hard, microgels are commonly modeled, at least in the small-deformation regime, within the simple framework of linear elasticity theory. Here we show that there exist conditions where its range of validity can be greatly extended, providing strong numerical evidence that microgels adsorbed at an interface follow the two-dimensional Hertzian theory, and hence behave like 2D elastic particles, up to very large deformations, in stark contrast to what found in bulk conditions. We are also able to estimate Young's modulus of the individual particles and, by comparing it with its counterpart in bulk conditions, we demonstrate a significant stiffening of the polymer network at the interface. Finally, by analyzing dynamical properties, we predict multiple reentrant phenomena: By a continuous increase of particle density, microgels first arrest and then refluidify due to the high penetrability of their extended coronas. We observe this anomalous behavior in a range of experimentally accessible conditions for small and loosely cross-linked microgels. The present work thus establishes microgels at interfaces as a new model system for fundamental investigations, paving the way for the experimental synthesis and research on unique highdensity liquidlike states. In addition, these results can guide the development of novel assembly and patterning strategies on surfaces and the design of novel materials with desired interfacial behavior.

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“…[30] Recent progress in synthesis enabled preparation nanogels with internal compartments and various shapes. [31][32][33][34][35] Furthermore,i sw as observed that the extreme softness of ultra-low cross-linked (ULC) nanogels leads to unique properties. [36] ULC nanogels exhibit high swellability and flexibility.…”

Section: Introductionmentioning

confidence: 99%

Stiffness Tomography of Ultra‐Soft Nanogels by Atomic Force Microscopy

et al. 2020

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The softness of nanohydrogels results in unique properties and recently attracted tremendous interest due to the multi‐functionalization of interfaces. Herein, we study extremely soft temperature‐sensitive ultra‐low cross‐linked (ULC) nanogels adsorbed to the solid/water interface by atomic force microscopy (AFM). The ultra‐soft nanogels seem to disappear in classical imaging modes since a sharp tip fully penetrates these porous networks with very low forces in the range of steric interactions (ca. 100 pN). However, the detailed evaluation of Force Volume mode measurements allows us to resolve their overall shape and at the same time their internal structure in all three dimensions. The nanogels exhibit an extraordinary disk‐like and entirely homogeneous but extremely soft structure—even softer than polymer brushes. Moreover, the temperature‐sensitive nanogels can be switched on demand between the ultra‐soft and a very stiff state.

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Anisotropic Hollow Microgels That Can Adapt Their Size, Shape, and Softness

Cited by 48 publications

References 67 publications

Synthesis and structure of temperature-sensitive nanocapsules

Synthesis and structure of temperature-sensitive nanocapsules

Microgels at Interfaces Behave as 2D Elastic Particles Featuring Reentrant Dynamics

Stiffness Tomography of Ultra‐Soft Nanogels by Atomic Force Microscopy

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