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

Reufer, Mathias; Dı́az-Leyva, Pedro; Lynch, Iseult; Scheffold, Frank

doi:10.1140/epje/i2008-10387-2

Cited by 81 publications

(95 citation statements)

References 39 publications

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“…Beyond the LCST the hydrodynamic radii at both conditions are rather similar, but still distinguishable. As reported in different studies [35][36][37], the cross-linking density is not homogeneous within the PNiPAM microgels. Indeed, they can be considered as core-shell particles, where the core is highly cross-linked while the shell consists of less cross-linked material with more dangling ends.…”

Section: A Contributions Of Electrostatics To the Swelling Behavior mentioning

confidence: 72%

Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels

et al. 2016

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We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility experiments are consistent with those obtained in Poisson-Boltzmann cell model calculations, effectively indicating that upon shrinking the number of counterions entrapped within the microgels increases. Remarkably, this behavior shows that the electrostatic energy per particle remains constant upon swelling or deswelling the microgel, resulting in a square root dependence of the net charge on the particle radius.

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Section: A Contributions Of Electrostatics To the Swelling Behavior mentioning

confidence: 72%

Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels

et al. 2016

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“…Water was used as a solvent since the polymer here solves well, despite the somewhat smaller quantum efficiency of the rhodamine dye in this environment (≈85%-95%) in comparison to that obtained with the ethylene glycol solvent used in our earlier experiments 11 . Above 32.4 °C temperature, the polymer within a temperature range of ≈0.2°C undergoes a phase transition to a state with collapsed polymer chains, and the associated molecular transport increases the specified refractive index from n≈1.35 to n≈1.46 29 . We have not seen evidence for a reduction of the cavity finesse caused by the dye-polymer phase transition.…”

Section: Methodsmentioning

confidence: 99%

Variable potentials for thermalized light and coupled condensates

et al. 2017

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For over a decade, cold atoms in lattice potentials have been an attractive platform to simulate phenomena known from solid state theory, as the Mott-insulator transition 1 . In contrast, the field of photonics usually deals with non-equilibrium physics 2-5 . Recent advances towards photonic simulators of solid state equilibrium effects include polariton double-site and lattice experiments 6-10 , as well as the demonstration of a photon condensate in a dye-filled microcavity 11,12 . Here we demonstrate a technique to create variable micropotentials for light using thermo-optic imprinting within an ultrahighreflectivity mirror microcavity filled with a dye-polymer solution that is compatible with photon gas thermalization. By repeated absorption-emission cycles photons thermalize to the temperature of the dye solution, and in a single microsite we observe a photon Bose-Einstein microcondensate. Effective interactions between the otherwise nearly noninteracting photons are observed due to thermo-optic effects, and in a double-well system tunnel coupling between sites is demonstrated, as well as the hybridization of eigenstates. Prospects of the new experimental platform include photonic structures in which photons thermalize into entangled manybody states 5 .Periodic potentials for light are at the core of proposals for Mott insulator physics for light, topological effects, as well as driven-dissipative phase transitions 13-18 . Exciton-polariton experiments, involving mixed states of matter and light under conditions of strong coupling, have used permanent semiconductor micro-structuring, as molecular beam epitaxy, metal depositing techniques, and mirror patterning 19,20 , to demonstrate double-well and periodic potentials 6-9 . In the regime of weak light-matter coupling, thermalization and Bose-Einstein condensation of a photon gas has been achieved in a high finesse microcavity containing dye molecules in liquid solution 11,12 .Here we demonstrate a microstructuring technique that allows to generate variable potentials for light within an optical high-finesse microcavity. The long photon lifetime enables the thermalization of photons and the demonstration of a microscopic photon condensate in a single localized site. We observe effective photon interactions as well as tunnel coupling between two microsites. The associated hybridization of eigenstates of the double well system is monitored spectroscopically.The scheme for thermo-optic imprinting of potentials is shown in Fig.1a. Within a microcavity of finesse near 35000, variations of the refractive index are induced through irradiation with a laser beam inducing heat from absorption in a 30nm thick silicon layer below one of the mirror surfaces. A thermosensitive polymer (PNIPAM) 21 , which undergoes

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“…The refractive index of the polymeric particles is estimated according to eq. [2] from the refractive indices of the corresponding homopolymers found in the literature [28][29][30] and the volume fractions of the core and shell as determined from TEM images. In the case of P(S-AA-NIPAM), the PAA/PNIPAM ratio in the shell is assumed to be identical to the feed ratio.…”

Section: Crystalline Colloidal Arraysmentioning

confidence: 99%

Responsive properties of crystalline colloidal arrays formed by core-shell microspheres with pH and temperature sensitivities

Bazin

Zhu

2012

Can. J. Chem.

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Polymeric microspheres responsive to pH and temperature changes have been prepared by a two-step surfactantfree emulsion polymerization with a polystyrene core and a hydrogel shell. The double sensitivity is achieved by the copolymerization in the shell layer of acrylic acid and N-isopropylacrylamide, which are pH-and thermo-responsive, respectively. Above a certain critical concentration, these microspheres are able to self-assemble into crystalline colloidal arrays, causing intense visible light diffraction. The behavior of these structures has been studied and correlated to the properties of the microspheres. The packing of these microspheres results in stimuli-sensitive colloidal crystals, with a behavior directly linked to the interactions between the particles and the surrounding media.Résumé : Des microsphères doublement sensibles et composées d'un coeur de polystyrène entouré d'une couche d'hydrogel ont été synthétisées par polymérisation en émulsion sans tensioactif. La double sensibilité a été obtenue grâce à la copolymérisation de l'acide acrylique et du N-isopropylacrylamide, tous deux connus pour être sensibles respectivement au pH et à la température. Au dessus d'une concentration critique, ces microsphères sont capables de s'auto-assembler pour former des cristaux colloïdaux et affichent des couleurs intenses dues à la diffraction de la lumière visible. Le comportement de ces structures a été étudié en rapport avec les propriétés des particules. L'empilement de ces microsphères donne des cristaux colloïdaux sensibles à leur environnement, propriété qui semble être liée à la nature des interactions entre les particules.Mots-clés : microsphères coeur-coquille, polymérisation en émulsion sans tensioactif, sensibilité au pH et à la température, cristaux colloïdaux.

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

Cited by 81 publications

References 39 publications

Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels

Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels

Variable potentials for thermalized light and coupled condensates

Responsive properties of crystalline colloidal arrays formed by core-shell microspheres with pH and temperature sensitivities

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