Intrinsic viscosity of small spherical polyelectrolytes: Proof for the intermolecular origin of the polyelectrolyte effect

Antonietti, Markus; Briel, Andreas; Förster, Stephan

doi:10.1063/1.472605

Cited by 68 publications

(98 citation statements)

References 30 publications

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“…A double logarithmic plot of the reduced viscosity versus the particle concentration presented in Fig. 6c shows a linear part, which is in fairly good agreement with an empirical scaling law proposed by Antonietti, for charged polystyrenesulfonate lattices (17,30):…”

Section: Viscosity Measurementssupporting

confidence: 88%

“…For c p > 0.8 w%, the reduced viscosity increases linearly with the particle concentration. This trend is also observed by Antonietti for charged lattices (17,28). The linear increase, in Fig.…”

Section: Viscosity Measurementssupporting

confidence: 82%

“…According to experiments in (17), α is found to be −0.25 for spherical particles and ∼ − 0.7 for linear polyelectrolytes. The α values, reported in Table 4, suggest that the starch microgels behave more or less like spherical particles in aqueous suspensions.…”

Section: Viscosity Measurementsmentioning

confidence: 95%

“…Rheological experiments on salt-free suspensions of starch microgels differing in crosslinking degree were performed to observe any effect of the cross-linking on the anomalous viscosity behavior, as already observed for polystyrenesulfonate lattices (17). In Fig.…”

Section: Viscosity Measurementsmentioning

confidence: 98%

“…However, for polyelectrolytes, the reduced viscosity is known to increase with dilution at low ionic strengths (14)(15)(16)(17). This anomalous viscosity behavior is explained in terms of changes of the polymer shape (14)(15)(16), or more recently, in terms of electrostatic effects (17). In this paper, reduced viscosity measurements were performed to determine whether starch microgels behave like charged polymers in aqueous suspensions.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and Properties of Starch-Based Colloidal Microgels

Dziechciarek

Soest²,

Philipse

2002

Journal of Colloid and Interface Science

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Novel starch microgels were prepared by emulsion cross-linking and characterized with respect to shape, volume, and mass density. Starch microgels appear to be negatively charged (∼−50 mV), with a particle size varying as a function of the type of cross-linker (ca. 0.25-10 µm). Environmental scanning electron microscopy observations show a dependence of the particle swelling on the cross-linking density. Viscosimetry reveals that starch microgels behave as charged polymers, where the reduced viscosity increases with dilution (anomalous viscosity behavior) for sufficiently low κa (ca. κa < 3), the ratio of the particle radius (a), and the Debye length (κ −1 ). Analogous results are obtained for reference-charged rigid silica spheres, which approach the hard sphere limit for increasing ionic strengths. The shape of the microgels appears to play a minor role in the anomalous viscosity behavior, which is more likely dominated by electrostatic effects. C 2002 Elsevier Science

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Section: Viscosity Measurementssupporting

confidence: 88%

Section: Viscosity Measurementssupporting

confidence: 82%

Section: Viscosity Measurementsmentioning

confidence: 95%

Section: Viscosity Measurementsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Preparation and Properties of Starch-Based Colloidal Microgels

Dziechciarek

Soest²,

Philipse

2002

Journal of Colloid and Interface Science

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Organized Functionalization of Mesoporous Silica Supports Using Prefabricated Metal-Polymer Modules

Whilton¹,

Berton

Bronstein

et al. 1999

Adv. Mater.

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The synthesis of inorganic oxides with controlled mesoporosity has developed since the beginning of the decade into one of the fastest moving research topics in modern materials chemistry. Whilst classical mesoporous silica synthesis employs low molecular weight organic amphiphiles as structure-directing agents in a sol±gel reaction mixture [1±4] to generate three-dimensional structures, the recent utilization of pre-assembled liquid crystalline surfactant [5] and polymer [6±8] templates has extended the synthetic possibilities. The use of high molecular weight block copolymers as templating agents has enabled the tailoring of pore size and framework architecture, extended the inorganic mesophase length scale and allowed the production of bulk inorganic monoliths as opposed to powders.[9±12] The larger pore sizes of these structures (2 to 50 nm) compared to microporous zeolitic materials (less than 1.2 nm) makes them particularly interesting for catalytic processes involving bulky substrates. The production of modified porous silicas containing well-dispersed noble metal nanoparticles and clusters distributed homogeneously throughout the pore channels has been a further challenge in the area of catalysis.[13±19] Conventional incorporation of metals involves the treatment of pre-formed solid supports, although in situ metal introduction techniques during support synthesis have also been reported. Heterogeneous metal distributions within the support, particle coalescence and decomposition, and catalyst leeching are some of the problems encountered during testing of materials prepared by these methods.Here we report on a specific method for direct inclusion of noble metal nanoparticles into a host framework which circumvents the need for post-synthesis functionalization of the support. A simple and convenient two-step reaction is presented in which prefabricated inorganic/organic hybrids are incorporated directly in a silica templating procedure to generate mesoporous silicas with high pore-connectivity and hosting a homogeneous distribution of noble metal particles. The approach combines the use of spherical functionalized polymer microgels [20] as nanosized exotemplates for the controlled growth of metal colloids [21] and as endotemplates during the casting of mesoporous sol±gel silicas.[22]A typical preparative procedure involves the initial synthesis of noble metal±polymer microgel hybrids. For this, poly(styrene sulfonate) microgels (70±90 nm in diameter) are loaded with noble metal ions and complexes. Reduction of the metal salts through the addition of sodium borohydride results in the formation and retention of metal particles within the microgel interior. These precursor hybrids are then added to a well-documented sol±gel recipe for the casting of mesoporous silica from ordered polystyreneblock-poly(ethylene oxide) mesophases utilizing tetramethoxysilane (TMOS) as the silica precursor.[8] The polymeric carrier mediates compatibility with the silicic network and ensures the positioning of the metal particl...

show abstract

Organized Functionalization of Mesoporous Silica Supports Using Prefabricated Metal–Polymer Modules

Whilton¹,

Berton

Bronstein

et al. 1999

Adv. Mater.

Self Cite

View full text Add to dashboard Cite

The synthesis of inorganic oxides with controlled mesoporosity has developed since the beginning of the decade into one of the fastest moving research topics in modern materials chemistry. Whilst classical mesoporous silica synthesis employs low molecular weight organic amphiphiles as structure-directing agents in a sol±gel reaction mixture [1±4] to generate three-dimensional structures, the recent utilization of pre-assembled liquid crystalline surfactant [5] and polymer [6±8] templates has extended the synthetic possibilities. The use of high molecular weight block copolymers as templating agents has enabled the tailoring of pore size and framework architecture, extended the inorganic mesophase length scale and allowed the production of bulk inorganic monoliths as opposed to powders. [9±12] The larger pore sizes of these structures (2 to 50 nm) compared to microporous zeolitic materials (less than 1.2 nm) makes them particularly interesting for catalytic processes involving bulky substrates.The production of modified porous silicas containing well-dispersed noble metal nanoparticles and clusters distributed homogeneously throughout the pore channels has been a further challenge in the area of catalysis. [13±19] Conventional incorporation of metals involves the treatment of pre-formed solid supports, although in situ metal introduction techniques during support synthesis have also been reported. Heterogeneous metal distributions within the support, particle coalescence and decomposition, and catalyst leeching are some of the problems encountered during testing of materials prepared by these methods.Here we report on a specific method for direct inclusion of noble metal nanoparticles into a host framework which circumvents the need for post-synthesis functionalization of the support. A simple and convenient two-step reaction is presented in which prefabricated inorganic/organic hybrids are incorporated directly in a silica templating procedure to generate mesoporous silicas with high pore-connectivity and hosting a homogeneous distribution of noble metal particles. The approach combines the use of spherical functionalized polymer microgels [20] as nanosized exotem-plates for the controlled growth of metal colloids [21] and as endotemplates during the casting of mesoporous sol±gel silicas. [22] A typical preparative procedure involves the initial synthesis of noble metal±polymer microgel hybrids. For this, poly(styrene sulfonate) microgels (70±90 nm in diameter) are loaded with noble metal ions and complexes. Reduction of the metal salts through the addition of sodium borohydride results in the formation and retention of metal particles within the microgel interior. These precursor hybrids are then added to a well-documented sol±gel recipe for the casting of mesoporous silica from ordered polystyreneblock-poly(ethylene oxide) mesophases utilizing tetramethoxysilane (TMOS) as the silica precursor. [8] The polymeric carrier mediates compatibility with the silicic network and ensures the positioning of the metal p...

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Intrinsic viscosity of small spherical polyelectrolytes: Proof for the intermolecular origin of the polyelectrolyte effect

Cited by 68 publications

References 30 publications

Preparation and Properties of Starch-Based Colloidal Microgels

Preparation and Properties of Starch-Based Colloidal Microgels

Organized Functionalization of Mesoporous Silica Supports Using Prefabricated Metal-Polymer Modules

Organized Functionalization of Mesoporous Silica Supports Using Prefabricated Metal–Polymer Modules

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