Surface Structure of Latex Particles Covered with Temperature-Sensitive Hydrogel Layers

Makino, Kimiko; Yamamoto, Satoshi; Fujimoto, Keiji; Kawaguchi, Haruma; Ohshima, Hiroyuki

doi:10.1006/jcis.1994.1291

Cited by 145 publications

(103 citation statements)

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“…This effect has been already observed in previous studies of similar particles, 14 for systems synthesized with a cationic initiator 13,16,17 or for PNIPAM microgels. 6 This is due to the residual charges originating from the synthesis of these particles and has been attributed to the remaining initiator fragments.…”

Section: B Interaction Of the Particlessupporting

confidence: 79%

“…Two types of particles can be prepared: either the particles consist totally of a PNIPAM network [5][6][7][8][9][10][11][12] or the PNIPAM-network is polymerized onto a solid core. [14][15][16][17][18][19] A great number of possible applications have been discussed for these systems that include widely separate fields as, e.g., protein adsorption. 20,21 They have also been recently used as a template for the reduction of metal nanoparticles [22][23][24] for applications in catalysis.…”

Section: Gelsmentioning

confidence: 99%

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Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions

Crassous

Siebenbürger

Ballauff

et al. 2006

The Journal of Chemical Physics

106

149

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We report on a comprehensive investigation of the flow behavior of colloidal thermosensitive core-shell particles at high densities. The particles consist of a solid core of poly͑styrene͒ onto which a network of cross-linked poly͑N-isopropylacrylamide͒ is affixed. Immersed in water the shell of these particles will swell if the temperature is low. Raising the temperature above 32°C leads to a volume transition within this shell which leads to a marked shrinking of the shell. The particles have well-defined core-shell structure and a narrow size distribution. The remaining electrostatic interactions due to a small number of charges affixed to the core particles can be screened by adding 0.05M KCl to the suspensions. Below the lower critical solution temperature at 32°C the particles are purely repulsive. Above this transition, a thermoreversible coagulation takes place. Lowering the temperature again leads to full dissociation of the aggregates formed by this process. The particles crystallize for effective volume fractions between 0.48 and 0.55. The crystallites can be molten by shear in order to reach a fluid sample again. The reduced shear stress measured in this metastable disordered state was found to be a unique function of the shear rate and the effective volume fraction. These reduced flow curves thus obtained can be described quantitatively by the theory of Fuchs and Cates ͓Phys. Rev. Lett. 89, 248304 ͑2002͔͒ which is based on the mode-coupling theory of the glass transition.

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Section: B Interaction Of the Particlessupporting

confidence: 79%

Section: Gelsmentioning

confidence: 99%

Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions

Crassous

Siebenbürger

Ballauff

et al. 2006

The Journal of Chemical Physics

106

149

View full text Add to dashboard Cite

show abstract

“…The above electrophoresis theory of soft particles has been applied to analyze the electrophoretic mobility data of biological colloids such as cells and their model particles [24][25][26][27][28][29][30][31][32][33][34][35]. Ohshima [36,37] proposed a theory of electrophoresis of soft particles in concentrated suspensions.…”

Section: Electrophoretic Mobility Of Soft Particlesmentioning

confidence: 99%

Theory of electrostatics and electrokinetics of soft particles

Ohshima

2009

Science and Technology of Advanced Materials

Self Cite

139

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We investigate theoretically the electrostatics and electrokinetics of a soft particle, i.e. a hard particle covered with an ion-penetrable surface layer of polyelectrolytes. The electric properties of soft particles in an electrolyte solution, which differ from those of hard particles, are essentially determined by the Donnan potential in the surface layer. In particular, the Donnan potential plays an essential role in the electrostatics and electrokinetics of soft particles. Furthermore, the concept of zeta potential, which is important in the electrokinetics of hard particles, loses its physical meaning in the electrokinetics of soft particles. In this review, we discuss the potential distribution around a soft particle, the electrostatic interaction between two soft particles, and the motion of a soft particle in an electric field.

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“…1,2 PNIPAM particles also show the dramatic change of their colloidal properties such as hydrophobicity, 3 particle size, 4 electrophoretic mobility, 5,6 colloidal stability, 7,8 rheology 9,10 etc. in response to temperature changes across the LCST.…”

mentioning

confidence: 99%

Preparation and Characterization of Micrometer-Sized Poly(N-isopropylacrylamide) Hydrogel Particles

2009

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The present study deals with preparation and swelling properties of micrometer-sized poly(N-isopropylacrylamide) (PNIPAM) hydrogel particles. Aqueous precipitation polymerization of NIPAM with N,N 0 -methylenebisacrylamide (MBAAm) was performed with varying electrolyte concentrations in the polymerization media. Sodium chloride was used as an electrolyte. According to the particle size analysis by transmission electron microscope, the particle size increased in the range of 0.55 to 1.60 mm with an increase in the electrolyte concentration up to 1.6 wt %. The concentration is based on the NIPAM monomer weight. Dynamic light scattering data showed that swelling ratio of PNIPAM hydrogel particles in water varied from 10 to 40 as the electrolyte concentration at particle preparation increased from 0 to 1.6 wt %. Time-course analysis of particle size showed that an increase in particle size would be caused by aggregation of smaller particles. In conclusion, micrometer-sized PNIPAM particles with high swelling capacity can be obtained by the addition of an electrolyte in polymerization media. Thermosensitive hydrogel particles containing poly(N-isopropylacrylamide) (PNIPAM) moieties have attracted much attention because they exhibit sharp and reversible volume phase transition at the lower critical solution temperature (LCST).1,2 PNIPAM particles also show the dramatic change of their colloidal properties such as hydrophobicity, 3 particle size, 4 electrophoretic mobility, 5,6 colloidal stability, 7,8 rheology 9,10 etc. in response to temperature changes across the LCST. These unique features make PNIPAM particles desirable for numerous applications, including controlled drug delivery, 11,12 control of enzymatic activity, 13,14 tunable optics, 15,16 and bioseparation. 17 Colloidally stable PNIPAM particles were first prepared by precipitation polymerization of NIPAM with N,N 0 -methylenebisacryamide (MBAAm) as a cross-linking agent in an aqueous medium at 60 to 70 C. 18 The resulting particles showed a volume phase transition at the LCST around 32 C. In precipitation polymerization, the initial state of the reaction mixture is a homogeneous solution. When a water-soluble initiator is added to the mixture, initiation and propagation take place largely in the homogeneous medium, followed by phase separation of growing PNIPAM chains because PNIPAM is insoluble in the medium at the reaction temperature. This leads to continuous nucleation and coagulation of the resulting nuclei to form larger particles. Since the first report, various methods have been studied so far for preparation of PNIPAM hydrogel particles. Pelton and co-workers reported that addition of surfactant gave smaller and more uniform PNIPAM particles than those obtained without surfactant.19 Yi et al. reported that monodisperse thermosensitive poly(styrene-co-NIPAM) particles with diameters in the range of 100 to 130 nm could be prepared by emulsifier-free emulsion polymerization with microwave irradiation. 20 In addition, many researchers have focuse...

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Surface Structure of Latex Particles Covered with Temperature-Sensitive Hydrogel Layers

Cited by 145 publications

References 0 publications

Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions

Thermosensitive core-shell particles as model systems for studying the flow behavior of concentrated colloidal dispersions

Theory of electrostatics and electrokinetics of soft particles

Preparation and Characterization of Micrometer-Sized Poly(N-isopropylacrylamide) Hydrogel Particles

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