Influence of the cross-linker content on adsorbed functionalised microgel coatings

Kyrey, Tetyana; Pipich, Vitaliy; Frielinghaus, Henrich; Witte, Judith; Wellert, Stefan; Klitzing, Regine von; Vezhlev, Egor; Koutsioubas, Alexandros; Feoktystov, Artem; Holderer, Olaf

doi:10.1016/j.polymer.2019.02.037

Cited by 29 publications

(25 citation statements)

References 48 publications

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“…These findings provide robust evidence of the reduced flexibility of the microgels at a liquid-liquid interface, an issue that up to now has either been extracted from indirect results or sometimes related to charge effects [68,69]. Instead, we directly prove that it is entirely attributable to the presence of the interface, where microgels assume a much more stretched configuration with respect to their standard arrangement in bulk.…”

Section: B Elasticity Theory Calculationssupporting

confidence: 55%

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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Section: B Elasticity Theory Calculationssupporting

confidence: 55%

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

et al. 2020

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“…In ref. 63, with GISANS, a domain-like internal structure of the adsorbed PNIPAM microgels was shown. Very recently, the presence of higher crosslink density clusters within a PNIPAM microgel was shown in real space using high resolution fluorescence microscopy and dye tagging.…”

Section: 2mentioning

confidence: 93%

Inner structure and dynamics of microgels with low and medium crosslinker content prepared via surfactant-free precipitation polymerization and continuous monomer feeding approach

et al. 2019

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The preparation of poly(N-isopropylacrylamide) microgels via classical precipitation polymerization (batch method) and a continuous monomer feeding approach (feeding method) leads to different internal crosslinker distributions, i.e., from core-shell-like to a more homogeneous one. The internal structure and dynamics of these microgels with low and medium crosslinker concentrations are studied with dynamic light scattering and small-angle neutron scattering in a wide q-range below and above the volume phase transition temperature. The influence of the preparation method, and crosslinker and initiator concentration on the internal structure of the microgels is investigated. In contrast to the classical conception where polymer microgels possess a core-shell structure with the averaged internal polymer density distribution within the core part, a detailed view of the internal inhomogeneities of the PNIPAM microgels and the presence of internal domains even above the volume phase transition temperature, when polymer microgels are in the deswollen state, are presented. The correlation between initiator concentration and the size of internal domains that appear inside the microgel with temperature increase is demonstrated. Moreover, the influence of internal inhomogeneities on the dynamics of the batch-and feeding-microgels studied with neutron spin-echo spectroscopy is reported.

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“…Notice that recently, 400–700 nm large and very low crosslinked PNIPAm particles prepared in the absence or with a very low amount of crosslinker BIS/NIPAM molar ratio = 0.005) were reported to be subjected to larger deformation during the absorption on a substrate than particles with a higher crosslinking density (e.g., BIS/NIPAM molar ratio = 0.05) [ 71 , 72 ]. This result may suggest that the particle size at which a change in behavior, from rigid sphere to random coil, may depend on the crosslinking degree.…”

Section: Resultsmentioning

confidence: 99%

“…Smooth continuous films can be obtained even with larger PNIPAm particles if their crosslinking degree is relatively low. PNIPAm b , which gives a continuous films but with particle edges well detectable, was prepared with an intermediate crosslinker amount (BIS/NIPAM molar ratio = 0.013) with respect to the samples studied by Richtering and Holderer groups [ 71 , 72 ]. In any case, further experiments would be necessary to confirm this hyphotesis.…”

Section: Resultsmentioning

confidence: 99%

Formation and Stability of Smooth Thin Films with Soft Microgels Made of Poly(N-Isopropylacrylamide) and Poly(Acrylic Acid)

et al. 2020

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In this work, soft microgels of Poly(N-Isopropylacrylamide) (PNIPAm) at two different sizes and of interpenetrated polymer network (IPN) composed of PNIPAm and Poly(Acrylic Acid) (PAAc) were synthesized. Then, solutions of these different types of microgels have been spin-coated on glass substrates with different degrees of hydrophobicity. PNIPAm particles with a larger diameter form either patches or a continuous layer, where individual particles are still distinct, depending on the dispersion concentration and spin speed. On the other, PNIPAm particles with a smaller diameter and IPN particles form a continuous and smooth film, with a thickness depending on the dispersion concentration and spin-speed. The difference in morphology observed can be explained if one considers that the microgels may behave as colloidal particles or macromolecules, depending on their size and composition. Additionally, the microgel size and composition can also affect the stability of the depositions when rinsed in water. In particular, we find that the smooth and continuous films show a stimuli-dependent stability on parameters such as temperature and pH, while large particle layers are stable under any condition except on hydrophilic glass by washing at 50 °C.

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Influence of the cross-linker content on adsorbed functionalised microgel coatings

Cited by 29 publications

References 48 publications

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

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

Inner structure and dynamics of microgels with low and medium crosslinker content prepared via surfactant-free precipitation polymerization and continuous monomer feeding approach

Formation and Stability of Smooth Thin Films with Soft Microgels Made of Poly(N-Isopropylacrylamide) and Poly(Acrylic Acid)

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