Structural changes in PNIPAM microgel particles as seen by SANS, DLS, and EM techniques

Kratz, Karl; Hellweg, Thomas; Eimer, Wolfgang

doi:10.1016/s0032-3861(01)00099-4

Cited by 249 publications

(250 citation statements)

References 24 publications

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“…Since PNIPAM is not soluble in hot water (T > 33 • ) the cross-linked PNIPAM gels collapse at elevated temperatures whereas at room temperature and below, water is a good solvent leading to a strong swelling. As a consequence of the relatively high cross-link density the swelling is less pronounced compared to some of the previous studies where swelling ratios up to four or five have been reported [20][21][22].…”

Section: Sample Preparationcontrasting

confidence: 59%

“…The effective interaction potential can be either attractive due to Van-der-Waals forces which leads to aggregation and phase separation [19], or in the presence of surface charges the particles can be stabilized in suspension. Upon lowering the temperature the particles swell by a factor of two to five in size [2,20]. If the initial particle density is sufficiently high the particle volume increase can drive the system from a liquid to a solid state.…”

Section: At Temperatures Well Above 35mentioning

confidence: 99%

“…We use a solid state laser TUI Optics DL we cannot exclude the possibility that some residual water remains bound to the polymer or that the particles are slightly deformed leading to a flattened shape [20]. Small errors in the alignment of the electron microscope or the calibration could also explain this difference.…”

Section: Static Light Scatteringmentioning

confidence: 99%

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Temperature-sensitive poly(N-Isopropyl-Acrylamide) microgel particles: A light scattering study

et al. 2008

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Abstract. We present a light scattering study of aqueous suspensions of microgel particles consisting of poly(N-Isopropyl-Acrylamide) cross-linked gels . The solvent quality for the particles depends on temperature and thus allows tuning of the particle size. The particle synthesis parameters are chosen such that the resulting high surface charge of the particles prevents aggregation even in the maximally collapsed state. We present results on static and dynamic light scattering (SLS/DLS) for a highly diluted sample and for diffuse optical transmission on a more concentrated system. In the maximally collapsed state the scattering properties are well described by Mie theory for homogenous hard spheres. Upon swelling we find that a radially inhomogeneous density profile develops. . Kn Physical gels and microgels -82.70.Gg Gels and sols PACS.

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Section: Sample Preparationcontrasting

confidence: 59%

Section: At Temperatures Well Above 35mentioning

confidence: 99%

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Temperature-sensitive poly(N-Isopropyl-Acrylamide) microgel particles: A light scattering study

et al. 2008

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“…7,29,37 While these techniques enable the determination of average particle diameters and pore sizes with high resolution and especially directly in solution (in contrast to, e.g., electron microscopy), it is not possible to investigate individual particles. Therefore these techniques are especially useful for highly monodisperse microgels and with a homogeneous swelling behaviour (i.e., homogeneous crosslinker density).…”

Section: 36mentioning

confidence: 99%

“…The most intensely studied thermoresponsive microgels are those containing poly(N-isopropylacrylamide) (PNIPAM). 7,8,[28][29][30][31] Below the volume phase transition temperature (VPTT) of 32 C PNI-PAM microgel particles consist of a loose network of crosslinked polymer chains with a comparably high solvent content and dangling surface chains. Above the VPTT the PNIPAM chains coil up, the particles deswell and the solvent is mainly released due to energetically more favourable internal interactions within the polymer network.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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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.

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Smart Gels

Bag

Saxena

2014

Kirk-Othmer Encyclopedia of Chemical Technology

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Stimuli‐responsive gels are known as smart gels. Such gels respond adaptively to a variety of external stimulation. Different classes of smart gels, according to the name of the stimulus, are thermoresponsive, pH‐responsive, photoresponsive, electroresponsive, magnetoresponsive gels, chemically activated gels, and others. Such smart gel materials are discussed in this article along with their synthesis, characterization, properties, and various applications such as drug delivery systems, thermoresponsive cell culture dishes, microfluidic gel photovoltaics, etc. The advantages and disadvantages of electroactive gels have been discussed for their application as actuators. Microporous and superporous gels, microgels/nanogels, shape‐memory and self‐healing gels, and fullerene (C 60 )‐containing nanostructured smart polymers/gels are also depicted in this article. The state‐of‐the‐art research and development of smart gels along with the opportunities and challenges of this emerging field of research are highlighted in this article.

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Structural changes in PNIPAM microgel particles as seen by SANS, DLS, and EM techniques

Cited by 249 publications

References 24 publications

Temperature-sensitive poly(N-Isopropyl-Acrylamide) microgel particles: A light scattering study

Temperature-sensitive poly(N-Isopropyl-Acrylamide) microgel particles: A light scattering study

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

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