Gerhard Platz - Academia.edu (original) (raw)
Papers by Gerhard Platz
Novel Vesicles from Single-Chain Surfactants
The Journal of Physical Chemistry B, 1999
ABSTRACT
Langmuir, 1998
The photoinduced optical anisotropy (POA) of novel aqueous azo dye systems which form chromonic m... more The photoinduced optical anisotropy (POA) of novel aqueous azo dye systems which form chromonic mesophases upon addition of methanol or sodium chloride was investigated. The phases were characterized between crossed polarizers. For further characterization rheological and holographic transient relaxation experiments were carried out. Distinctive differences in the hologram formation and decay were found for phases which exhibit the same texture in polarization microscopy. The generated holographic gratings could be assigned to either photoinduced phase transitions or an alignment of optical axes. In the present study we concentrate on a comparison of phases with the same macroscopic birefringence; results are discussed in comparison with models in the literature.
Phase behavior and stability of concentrated emulsions
Journal of Colloid and Interface Science, 1989
... RUCKENSTEIN,*'1 GERLINDE EBERT,t AND G. PLATZt* State University of New York at Buff... more ... RUCKENSTEIN,*'1 GERLINDE EBERT,t AND G. PLATZt* State University of New York at Buffalo, Department of Chemical Engineering, Buffalo, New ... Experimentalresults are presented in some detail for SDS and Triton X-100 and in tess detail for a large number ofsurfactants. ...
Langmuir, 1998
Calcium dodecyl sulfate (CDS) is insoluble both in water and in alcohols at room temperature. How... more Calcium dodecyl sulfate (CDS) is insoluble both in water and in alcohols at room temperature. However, it can be dissolved up to high concentrations in mixtures of water and ethanol, propanol, or butanol. No liquid-crystalline phases are formed with ethanol and propanol at 25°C but are observed with butanol at higher concentrations of CDS. With pentanol and hexanol, lamellar phases are observed, which can be swollen largely. Neutron scattering measurements of phases with a weight ratio CDS:hexanol) 1:1 show stiff lamellae in the concentration range of 1.5-25 wt % CDS. The repeat distance grows linearly with dilution. The effective thickness for the hydrocarbon part of the lamellae decreases to some extent at high CDS concentrations.
Eine Sto?wllenapparatur zur Untersuchung von Shcnellen Reaktionen in L?sungen
Colloid Polym Sci, 1974
The Kinetics of Micelle Formation
Anianssons equations for the fast monomer relaxation process in micellar systems are explained in... more Anianssons equations for the fast monomer relaxation process in micellar systems are explained in an elementary way. The relations which must exist between distribution curves and rate constants for the stepwise aggregation processes in order to obtain one single relaxation time are discussed. Anianssons method is finally applied to the general case of a multistep process with stepwise monomer association.
Untersuchung von Trübungserscheinungen im Einphasengebiet wäßriger Lösungen nichtionogener Tenside
Berichte der Bunsengesellschaft/Physical Chemistry Chemical Physics
ABSTRACT
Highly Ordered Parabolic Focal Conics in Lyotropic Systems
Langmuir, 1996
ABSTRACT
Swelling Behavior of Lamellar Phases with Calcium Dodecyl Sulfate, Heptanol or Octanol, and Water
Langmuir, 1999
ABSTRACT
Investigation of the L 3 Phase in Systems Containing Calcium Dodecyl Sulfate, Alcohol, and Water
Langmuir, 2001
ABSTRACT
Kinetic investigations at the cloud point of nonionic surfactants
Journal of Colloid and Interface Science, 1981
ABSTRACT
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
The influence of sodium counterions on the highly swollen lamellar phases in the system consistin... more The influence of sodium counterions on the highly swollen lamellar phases in the system consisting of calcium dodecyl sulfate (CDS), octanol, and water was investigated at 25°C. Highly dilute, iridescent lamellar phases could be obtained with CDS/sodium dodecyl sulfate (SDS) weight ratios above 85/15. There is no continuous transition from the swollen lamellar phase to the more highly dilute iridescent phase, instead, there is a miscibility gap with coexisting lower iridescent and upper swollen lamellar phases which is more pronounced in systems containing sodium counterions. Also, the CDS/decanol/water system was investigated, in which we found a novel, highly swollen lamellar and even an iridescent phase in an extremely narrow region in the phase diagram at 25°C. In contrast to the pentanol-octanol systems, the decanol system displays an L 3 phase at elevated, but not at room temperature.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1994
Dilute C,2114 alkyl polyglucoside (Glucopon6000S ®) solutions containing small amounts of fatty a... more Dilute C,2114 alkyl polyglucoside (Glucopon6000S ®) solutions containing small amounts of fatty alcohols (hydrocarbon chain length greater than 4) show three different lamellar phases (L, 1, L, L,,,) which are characterized by increasing fatty alcohol : surfactant ratios. The middle lamellar phase appears, in some aspects, like a mixture of the lower and upper lamellar phases. The lower and middle lamellar phases are optically biaxial and are therefore probably in tilted crystalline states. The upper lamellar phase is in the liquid state and is uniaxial. On the addition of alkyl sulphates together with the appropriate amount of the fatty alcohols, to a 5% alkyl polyglucoside solution the middle lamellar phase predominates. Pentanol and hexanol favour the upper lamellar phase while longer-chain fatty alcohols favour the lower lamellar phase. A cholesteric phase with characteristic fingerprint texture appears in highly concentrated surfactant solutions containing decanol or higher fatty alcohols. The characteristic fingerprint texture of this phase is due to myelinic figures which occur in the two-phase region between the lower lamellar phase and an isotropic phase. The fingerprints can be oriented in strong magnetic fields. The cholesteric phase interacts strongly with polarized light which is travelling in the direction of the helical axis.
Book Review: Surfactant Science and Technology. By D. Myers
Angewandte Chemie International Edition in English, 1989
Book Review: Foams and Biliquid Foams-Aphrons. By F. Sebba
Angewandte Chemie International Edition in English, 1989
Advances in Colloid and Interface Science, 2003
This article presents an overview over research on binary and ternary anionic surfactant systems ... more This article presents an overview over research on binary and ternary anionic surfactant systems with calcium counterions over the past 30 years, with a focus on recent studies. General phase behavior of surfactants and the underlying electrostatics are given a synoptical treatment. With N-alkyl amide sulfates, a new class of surfactants is described in which the Krafft point of the calcium surfactant is lower than that of its sodium counterpart. The exemplary ternary systems treated in depth are calcium dodecyl poly(oxyethylene) sulfatey C betainywater, calcium dodecyl sulfateymedium-chain alcoholywater, and a-sulfonated 14 methyl myristate, Ca salty2-ethylhexylmonoglycerideywater. It is shown that ternary 2q systems of this kind frequently show elements of the behavior of non-ionic or double-chain surfactants, e.g. a tendency toward micellar growth and the formation of vesicular and lamellar structures, the existence of highly swollen, iridescent lamellar phases and also the formation of L (sponge) phases. This is explained by the high degree of membrane 3 association of the doubly-charged calcium ions and the resulting low apparent surface charge density of the surfactantywater interface. The methods discussed in this article include smallangle neutron scattering (SANS), UV-Vis photometry, differential scanning calorimetry, oscillating rheometry, conductivity and electric birefringence measurements and electron microscopy.
Colloid & Polymer Science, 1994
Electron microscopic observations and classical light-scattering measurements have been carried o... more Electron microscopic observations and classical light-scattering measurements have been carried out for dodecyldimethylaminoxide/hexanol/ water mixtures in the concentration range where iridescent colors occur. This system has two different iridescent phases. The iridescent phase with more hexanol forms quickly, and the phase with less hexanol forms very slowly. Three different isotropic phases which show strong flow birefringence are found near both iridescent phases. The electron microscopic pictures show clearly that only one of these isotropic phases with strong flow birefringence is a bicontinuous sponge phase (L3h-phase). This is the phase which comes out by adding some alkanol to the upper lameUar phase. The flow birefringent phase below the lower lamellar phase forms unilamellar vesicles. The flow birefringent phase which occurs between both iridescent phases contains multilamellar vesicles and is shown to be a precursor of a lamellar phase.
Preparation of alkyl a- and �- d-glucopyranosides, thermotropic properties and X-ray analysis
Carbohyd Res, 1998
Monohydrates of heptyl to decyl α-d-glucopyranosides as obtained from product mixtures of the Fis... more Monohydrates of heptyl to decyl α-d-glucopyranosides as obtained from product mixtures of the Fischer glucosylation were crystallized from water at the Krafft point. The results of the single-crystal X-ray analysis of anhydrous α anomers and their monohydrates provide for a better understanding of crystal formation and stability of their hydrates. The preparation of alkyl β-d-glucopyranosides—without concomitant formation of α anomers as by-products—has been described. The thermotropic properties have been investigated for the α compounds and their monohydrates, and for the β-d-glucopyranosides.
Carbohyd Res, 1999
Thermotropic properties and crystal structures of alkyl α-d-glucopyranosides and their hydrates w... more Thermotropic properties and crystal structures of alkyl α-d-glucopyranosides and their hydrates were estimated by X-ray, DSC and thermogravimetric measurements (TGA). Monohydrates rapidly lose their crystal water several degrees below the melting point of the anhydrous glucopyranosides. The melting points of the monohydrates measured in DSC pressure cells (chain length longer than seven) are lower, and the clearing points higher than those of the anhydrous glucosides. Layer distances of smectic and crystalline phases of anhydrous compounds were established. Melting points, densities and layer distances of the crystalline anhydrous glucopyranosides display strong even–odd effects. The strong decrease of these effects in the case of the monohydrates can be elucidated by the results of X-ray crystal structure analysis.
Novel Vesicles from Single-Chain Surfactants
The Journal of Physical Chemistry B, 1999
ABSTRACT
Langmuir, 1998
The photoinduced optical anisotropy (POA) of novel aqueous azo dye systems which form chromonic m... more The photoinduced optical anisotropy (POA) of novel aqueous azo dye systems which form chromonic mesophases upon addition of methanol or sodium chloride was investigated. The phases were characterized between crossed polarizers. For further characterization rheological and holographic transient relaxation experiments were carried out. Distinctive differences in the hologram formation and decay were found for phases which exhibit the same texture in polarization microscopy. The generated holographic gratings could be assigned to either photoinduced phase transitions or an alignment of optical axes. In the present study we concentrate on a comparison of phases with the same macroscopic birefringence; results are discussed in comparison with models in the literature.
Phase behavior and stability of concentrated emulsions
Journal of Colloid and Interface Science, 1989
... RUCKENSTEIN,*'1 GERLINDE EBERT,t AND G. PLATZt* State University of New York at Buff... more ... RUCKENSTEIN,*'1 GERLINDE EBERT,t AND G. PLATZt* State University of New York at Buffalo, Department of Chemical Engineering, Buffalo, New ... Experimentalresults are presented in some detail for SDS and Triton X-100 and in tess detail for a large number ofsurfactants. ...
Langmuir, 1998
Calcium dodecyl sulfate (CDS) is insoluble both in water and in alcohols at room temperature. How... more Calcium dodecyl sulfate (CDS) is insoluble both in water and in alcohols at room temperature. However, it can be dissolved up to high concentrations in mixtures of water and ethanol, propanol, or butanol. No liquid-crystalline phases are formed with ethanol and propanol at 25°C but are observed with butanol at higher concentrations of CDS. With pentanol and hexanol, lamellar phases are observed, which can be swollen largely. Neutron scattering measurements of phases with a weight ratio CDS:hexanol) 1:1 show stiff lamellae in the concentration range of 1.5-25 wt % CDS. The repeat distance grows linearly with dilution. The effective thickness for the hydrocarbon part of the lamellae decreases to some extent at high CDS concentrations.
Eine Sto?wllenapparatur zur Untersuchung von Shcnellen Reaktionen in L?sungen
Colloid Polym Sci, 1974
The Kinetics of Micelle Formation
Anianssons equations for the fast monomer relaxation process in micellar systems are explained in... more Anianssons equations for the fast monomer relaxation process in micellar systems are explained in an elementary way. The relations which must exist between distribution curves and rate constants for the stepwise aggregation processes in order to obtain one single relaxation time are discussed. Anianssons method is finally applied to the general case of a multistep process with stepwise monomer association.
Untersuchung von Trübungserscheinungen im Einphasengebiet wäßriger Lösungen nichtionogener Tenside
Berichte der Bunsengesellschaft/Physical Chemistry Chemical Physics
ABSTRACT
Highly Ordered Parabolic Focal Conics in Lyotropic Systems
Langmuir, 1996
ABSTRACT
Swelling Behavior of Lamellar Phases with Calcium Dodecyl Sulfate, Heptanol or Octanol, and Water
Langmuir, 1999
ABSTRACT
Investigation of the L 3 Phase in Systems Containing Calcium Dodecyl Sulfate, Alcohol, and Water
Langmuir, 2001
ABSTRACT
Kinetic investigations at the cloud point of nonionic surfactants
Journal of Colloid and Interface Science, 1981
ABSTRACT
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001
The influence of sodium counterions on the highly swollen lamellar phases in the system consistin... more The influence of sodium counterions on the highly swollen lamellar phases in the system consisting of calcium dodecyl sulfate (CDS), octanol, and water was investigated at 25°C. Highly dilute, iridescent lamellar phases could be obtained with CDS/sodium dodecyl sulfate (SDS) weight ratios above 85/15. There is no continuous transition from the swollen lamellar phase to the more highly dilute iridescent phase, instead, there is a miscibility gap with coexisting lower iridescent and upper swollen lamellar phases which is more pronounced in systems containing sodium counterions. Also, the CDS/decanol/water system was investigated, in which we found a novel, highly swollen lamellar and even an iridescent phase in an extremely narrow region in the phase diagram at 25°C. In contrast to the pentanol-octanol systems, the decanol system displays an L 3 phase at elevated, but not at room temperature.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1994
Dilute C,2114 alkyl polyglucoside (Glucopon6000S ®) solutions containing small amounts of fatty a... more Dilute C,2114 alkyl polyglucoside (Glucopon6000S ®) solutions containing small amounts of fatty alcohols (hydrocarbon chain length greater than 4) show three different lamellar phases (L, 1, L, L,,,) which are characterized by increasing fatty alcohol : surfactant ratios. The middle lamellar phase appears, in some aspects, like a mixture of the lower and upper lamellar phases. The lower and middle lamellar phases are optically biaxial and are therefore probably in tilted crystalline states. The upper lamellar phase is in the liquid state and is uniaxial. On the addition of alkyl sulphates together with the appropriate amount of the fatty alcohols, to a 5% alkyl polyglucoside solution the middle lamellar phase predominates. Pentanol and hexanol favour the upper lamellar phase while longer-chain fatty alcohols favour the lower lamellar phase. A cholesteric phase with characteristic fingerprint texture appears in highly concentrated surfactant solutions containing decanol or higher fatty alcohols. The characteristic fingerprint texture of this phase is due to myelinic figures which occur in the two-phase region between the lower lamellar phase and an isotropic phase. The fingerprints can be oriented in strong magnetic fields. The cholesteric phase interacts strongly with polarized light which is travelling in the direction of the helical axis.
Book Review: Surfactant Science and Technology. By D. Myers
Angewandte Chemie International Edition in English, 1989
Book Review: Foams and Biliquid Foams-Aphrons. By F. Sebba
Angewandte Chemie International Edition in English, 1989
Advances in Colloid and Interface Science, 2003
This article presents an overview over research on binary and ternary anionic surfactant systems ... more This article presents an overview over research on binary and ternary anionic surfactant systems with calcium counterions over the past 30 years, with a focus on recent studies. General phase behavior of surfactants and the underlying electrostatics are given a synoptical treatment. With N-alkyl amide sulfates, a new class of surfactants is described in which the Krafft point of the calcium surfactant is lower than that of its sodium counterpart. The exemplary ternary systems treated in depth are calcium dodecyl poly(oxyethylene) sulfatey C betainywater, calcium dodecyl sulfateymedium-chain alcoholywater, and a-sulfonated 14 methyl myristate, Ca salty2-ethylhexylmonoglycerideywater. It is shown that ternary 2q systems of this kind frequently show elements of the behavior of non-ionic or double-chain surfactants, e.g. a tendency toward micellar growth and the formation of vesicular and lamellar structures, the existence of highly swollen, iridescent lamellar phases and also the formation of L (sponge) phases. This is explained by the high degree of membrane 3 association of the doubly-charged calcium ions and the resulting low apparent surface charge density of the surfactantywater interface. The methods discussed in this article include smallangle neutron scattering (SANS), UV-Vis photometry, differential scanning calorimetry, oscillating rheometry, conductivity and electric birefringence measurements and electron microscopy.
Colloid & Polymer Science, 1994
Electron microscopic observations and classical light-scattering measurements have been carried o... more Electron microscopic observations and classical light-scattering measurements have been carried out for dodecyldimethylaminoxide/hexanol/ water mixtures in the concentration range where iridescent colors occur. This system has two different iridescent phases. The iridescent phase with more hexanol forms quickly, and the phase with less hexanol forms very slowly. Three different isotropic phases which show strong flow birefringence are found near both iridescent phases. The electron microscopic pictures show clearly that only one of these isotropic phases with strong flow birefringence is a bicontinuous sponge phase (L3h-phase). This is the phase which comes out by adding some alkanol to the upper lameUar phase. The flow birefringent phase below the lower lamellar phase forms unilamellar vesicles. The flow birefringent phase which occurs between both iridescent phases contains multilamellar vesicles and is shown to be a precursor of a lamellar phase.
Preparation of alkyl a- and �- d-glucopyranosides, thermotropic properties and X-ray analysis
Carbohyd Res, 1998
Monohydrates of heptyl to decyl α-d-glucopyranosides as obtained from product mixtures of the Fis... more Monohydrates of heptyl to decyl α-d-glucopyranosides as obtained from product mixtures of the Fischer glucosylation were crystallized from water at the Krafft point. The results of the single-crystal X-ray analysis of anhydrous α anomers and their monohydrates provide for a better understanding of crystal formation and stability of their hydrates. The preparation of alkyl β-d-glucopyranosides—without concomitant formation of α anomers as by-products—has been described. The thermotropic properties have been investigated for the α compounds and their monohydrates, and for the β-d-glucopyranosides.
Carbohyd Res, 1999
Thermotropic properties and crystal structures of alkyl α-d-glucopyranosides and their hydrates w... more Thermotropic properties and crystal structures of alkyl α-d-glucopyranosides and their hydrates were estimated by X-ray, DSC and thermogravimetric measurements (TGA). Monohydrates rapidly lose their crystal water several degrees below the melting point of the anhydrous glucopyranosides. The melting points of the monohydrates measured in DSC pressure cells (chain length longer than seven) are lower, and the clearing points higher than those of the anhydrous glucosides. Layer distances of smectic and crystalline phases of anhydrous compounds were established. Melting points, densities and layer distances of the crystalline anhydrous glucopyranosides display strong even–odd effects. The strong decrease of these effects in the case of the monohydrates can be elucidated by the results of X-ray crystal structure analysis.