Interactions between cationic starch and anionic surfactants
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Date
2001-03-02
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Language
en
Pages
107, [74]
Series
Reports / Helsinki University of Technology, Laboratory of Forest Products Chemistry. Series A, 12
Abstract
The interactions between cationic starch (CS) and anionic surfactants and their mixtures were studied by using surface tension, solution viscosity and dynamic light scattering (DLS) measurements. The composition and structure of the complexes of CS and surfactants were studied by using phase equilibrium determination, small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) measurements. Critical association concentrations (cac) are well below the critical micellisation concentrations (cmc) of the surfactants. Associative phase separation occurs in extremely dilute systems when the charge ratio between the surfactants and the polymer is close to one. The effect of mixing on micellisation of the binary surfactant solution can be described by taking into account the effects of the volume difference between the hydrocarbon chains. The separated phase is a hydrophobic, viscous, gel-like complex containing less than 60 w% of water. With mixed surfactants, the more surface-active component is enriched in the complex phase. The gel is dissolved entirely or partly when excess surfactant is added with charge reversal mechanism. The mixed micelles of alkanoates are prolate ellipsoids with the longer-chain surfactant enriched in the end-cups of the ellipsoid. In dilute solutions CS molecules have a helical conformation. The core of CS/surfactant aggregates is formed by surfactant monomers and the surrounded shell by CS-chains. The structure of the complexes in dilute solutions resembles the inclusion complexes of amylose and surfactants. The charge neutralized CS-surfactant complexes consists of lyotropic liquid crystalline phase. The mesophases are the same as the pure surfactants form without any added polymer (hexagonal, lamellar or cubic), but they form with CS at lower surfactant concentrations. The gel-like CS-surfactant complex phases have high viscosity and elasticity. Their rheological behaviour is described by the Hershel-Bulkley model.Description
Keywords
cationic starch, anionic surfactants, interactions, complexes, structure, phase equilibrium, viscosity, SAXS, SANS, DLS
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Parts
- Merta, J.; Stenius, P. (1995), Interactions between cationic starch and anionic surfactants. 1. Phase equilibria and surface tensions. Colloid Polym. Sci. 273, 974-983.
- Merta, J.; Stenius, P. (1997), Interactions between cationic starch and anionic surfactants 2. Viscosity and aggregate size in dilute solutions. Colloids Surfaces A: Physicochem. Eng. Aspects 122, 243-255. [article2.pdf] © 1997 Elsevier Science. By permission.
- Merta, J., Pirttinen, E.; Stenius, P. (1999), Interactions between cationic starch and anionic surfactants. III. Rheology and structure of the complex phase. J. Dispersion Sci. and Techn. 20, 677-697.
- Merta, J. and Stenius, P. (1999), Interactions between cationic starch and mixed anionic surfactants. Colloids Surfaces A: Physicochem. Eng. Aspects 149, 367-377. [article4.pdf] © 1999 Elsevier Science. By permission.
- Merta, J., Torkkeli, M., Ikonen, T., Serimaa, R. and Stenius, P. (2001). The structure of cationic starch (CS)/anionic surfactant complexes studied by small angle X-ray scattering. Macromolecules. Accepted. [article5.pdf] © 2001 American Chemical Society. By permission.
- Merta, J., Garamus, V., Willumeit, R., Kuklin, A. and Stenius, P. (2000). Determination of the Structure of Complexes Formed by a Cationic Polymer and Mixed Anionic Surfactants by SANS. Langmuir 16, 10061-10068. [article6.pdf] © 2000 American Chemical Society. By permission.