| 1. |
- Friman, Rauno, et al.
(författare)
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Oppositely charged surfactant-polyelectrolyte systems as model systems for mesoscopically ordered surfactant-silicates
- 2006
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 291:1-3, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- Due to the strongly kinetic nature of the chemical events leading to the formation of mesoscopically ordered inorganic-surfactant composite materials, detailed studies on the interdependency between the degree of inorganic condensation and the co-operative self-assembly is difficult to perform. We have therefore undertaken a study where organic polyelectrolytes are used as models for the inorganic oligomeric/polymeric species and studied the phase behavior of negatively charged polyacrylate positively charged surfactant complexes in aqueous solution as a function of polyelectrolyte molar mass. Dodecyltrimethyl ammonium chloride was used as the surfactant. The toluene solubilization capacity of the complexes were also determined, and a clear dependency on the (poly)electrolyte molar mass was found. The results can be used to explain many of the observed features observed for evolving silicate-surfactant under kinetic control. It is suggested that electrostatic screening effects dominate at low degrees of silicate condensation, while the stabilizing effect of the polyelectrolyte becomes increasingly dominant upon further silicate condensation. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Lund, Kristina, 1976-
(författare)
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Structural and Morphological Studies of Mesoporous Crystals
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mesoporous silica and carbon have been synthesised and characterised by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) and nitrogen adsorption. Surface structure, size and shape (morphology) of particles have been of special interest in this work. These parameters are of importance in understanding the growth mechanism and structural characteristics of mesoporous materials overall, which has been the main aim of this thesis.The novel synthetic system involving preparation of AMS (anionic surfactant-templated silica) crystals, where the non-toxic N-acyl-amino acids are used as surfactant together with a co-structure directing agent, was investigated in two different surfactant systems. Particle size and shape of AMS solids were controlled through the addition of a polymeric dispersant, which slowed down the system dynamics. However, the response for the two synthetic systems investigated, proved to be different. Nanoparticles of cage-type cubic Fd-3m crystals were obtained in one system, whereas facetted particles formed in a near-to-equilibrium growth in the bicontinuous cubic Ia-3d case. The surface fine structure of mesoporous silica was observed by high resolution SEM, leading to an understanding of the pore accessibility at the particle surface of SBA-15 silica. Furthermore, discrepancies in the XRD patterns of mesoporous tube-type carbon CMK-5 with different pore diameters were observed. XRD patterns displaying accidental extinction of the 10 reflection were observed in CMK-5 samples prepared with the widest pore diameter. An analytical approach was formulated in order to simulate the variation of XRD intensity for carbon crystals with p6mm symmetry. TEM observations of inner and outer diameter of the carbon tubes were used to interpret the diminishing of certain reflections and we observed good agreement between experimental observations and our calculations.
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