Structural properties of thermoresponsive poly(<i>N</i>-isopropylacrylamide)-poly(ethyleneglycol) microgels

Clara-Rahola, Joaquim; Fernández‐Nieves, Alberto; Sierra‐Martin, Benjamin; South, Antoinette B.; Lyon, L. Andrew; Kohlbrecher, J.; Barbero, Antonio Fernández

doi:10.1063/1.4723686

Cited by 34 publications

(32 citation statements)

References 29 publications

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“…As pointed out by Clara-Rahola et al, 61 highly swollen PNiPAM microgels are better described as star polymers or dendrimers than as fuzzy spheres. Furthermore Willner et al 62 could show that the form factor of large stars show features of the spherical superstructure of the stars.…”

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confidence: 90%

On tuning microgel character and softness of cross-linked polystyrene particles

et al. 2017

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Polystyrene (PS) microgel colloids have often been used successfully to model hard sphere behaviour even though the term "gel" invokes inevitably the notion of a more or less soft, deformable object. Here we systematically study the effect of reducing the cross-link density from 1 : 10 (1 cross-link per 10 monomers) to 1 : 100 on particle interactions and "softness". We report on the synthesis and purification of 1 : 10, 1 : 25, 1 : 50, 1 : 75 and 1 : 100 cross-linked PS particles and their characterization in terms of single particle properties, as well as the behaviour of concentrated dispersions. We are able to tune particle softness in the range between soft PNiPAM-microgels and hard PMMA particles while still allowing the mapping of the microgels onto hard sphere behavior with respect to phase diagram and static structure factors. This is mainly due to a rather homogeneous radial distribution of cross-links in contrast to PNiPAM microgels where the cross-link density decreases radially. We find that up to a cross-link density of 1 : 50 particle form factors are perfectly described by a homogeneous sphere model whereas 1 : 75 and 1 : 100 cross-linked spheres are slightly better described as fuzzy spheres. However the fuzziness is rather small compared to typical PNiPAM microgels so that a hard sphere mapping still holds even for these low cross-link densities. Finally, by varying the reaction conditions - changing from batch to semibatch emulsion polymerization and varying the feed rate or by adjusting the monomer to initiator ratio we can tune the fuzziness or significantly alter the inner structure to a more open, star-like architecture.

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confidence: 90%

On tuning microgel character and softness of cross-linked polystyrene particles

et al. 2017

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“…characterized by scattering methods such as static and dynamic light scattering, elastic and quasielastic small angle neutron scattering [11,14,40,90,109], NMR [92]. Corresponding measurements in the adsorbed state require the use of imaging techniques, ellipsometry, quartz crystall microgravimetry, and other surface sensitive techniques.…”

Section: Introductionmentioning

confidence: 99%

Responsive Microgels at Surfaces and Interfaces

Wellert

Richter

Hellweg

et al. 2014

Zeitschrift Für Physikalische Chemie

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Stimuli responsive surface structures attract increasing attention due to a large variety of envisioned applications. The controlled organization of poly(N-isopropyl acrylamid), PNIPAM microgel particles at solid surfaces inspired numerous research activities. In this review article, we briefly discuss the swelling/deswelling properties of adsorbed microgel particles in comparison to the behavior in the bulk phase. The presence of the solid interface highly influences and changes their behavior with respect to the properties in solution. Furthermore, the confinement on a solid substrate allows the direct and in-situ investigation of the mechanical properties of the microgel particles. Additionally, we briefly review the research on microgel particles at liquid interfaces. At these interfaces new interesting effects occur. Moreover, we discuss some interesting work on potential applications. In this context, microgel particles are often used as an active component for responsive coatings of various functionality envisioning applications, e.g. in medicine, biotechnology, and nanooptics.Zusammenfassung: Responsive Oberflächenmaterialien finden aufgrund der damit verbundenen potentiellen technischen Anwendungsmöglichkeiten große Beachtung in der aktuellen Forschung. Die Möglichkeit, kolloidale Gelpartikel aus poly(N-Isopropylacrylamid), PNIPAM an festen Oberflächen kontrolliert anzuordnen, inspirierte vielfältige Forschungsakivitäten. In diesem Übersichtsartikel diskutieren wir das Quellverhalten adsorbierter Mikrogelpartikel im Vergleich zu

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“…This theory fitted successfully their SANS studies on PNIPAM nanogels and since then, it is one of the most employed models by different authors [9,17]. Nevertheless, Boyko et al, also consider the nanogel particle as an inhomogeneous structure due to a cross-linker density gradient, so they use a slightly modified expression for IðqÞ [13]:…”

Section: Introductionmentioning

confidence: 90%