Juha Merta

Interactions between cationic starch and mixed anionic surfactants

The surface tensions and the phase equilibria of dilute aqueous cationic starch (CS)/surfactant systems were investigated. The degree of substitution of the CS varied from 0.014 to 0.772. The surfactants investigated were sodium dodecyl sulphate (SDS), potassium octanoate (KOct), potassium dodecanoate (KDod) and sodium oleate (NaOl). The concentrations of CS were 0.001, 0.01 and 0.1 w%.

Synthesis and characterization of copper sulfide nanocrystallites with low sintering temperatures

To study nano-inks with relatively low sintering temperatures for fabrication of functional electronics on paper by inkjet printing technology, we have successfully prepared copper sulfide nanocrystallites protected by self-assembled monolayers. Systematic characterization was performed on as-prepared nanoparticles by FTIR, NMR, thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and wide-angle X-ray scattering (WAXS) with heating. The copper sulfide nanocrystallites with crystal sizes <1.5 nm show a hexagonal Cu2S phase at low temperatures but undergo significant consolidation/crystallization from 100 to 240 °C, accompanying a transformation from the hexagonal Cu2S phase to the cubic Cu1.8S phase when heated up to ca. 150 °C. The protective ligand burnout during heating is closely associated with the nanocrystallite consolidation. Further, the copper sulfide nanoparticles were deposited on paper and sintered at 240 °C in air. The sintered particles are composed of large crystals of cubic Cu1.8S with no serious degradation due to oxidation. The resistivity of the sintered particles was of the order of 1 × 10−5 (Ω m).

Complexation between lignosulfonates and cationic surfactants and its influence on emulsion and foam stability

Abstract The association between sodium lignosulfonates and cationic as well as nonionic surfactants (quaternary ammonium bromides, cetylpyridinium chloride (CPC)) has been investigated by means of surface tension measurements, with additional information from measurements of viscosities and electrophoretic mobilities. A strong interaction is revealed between the lignosulfonate (LS) and micelles of the cationic surfactant, whereas no interaction is found in the case of a polyethyleneoxide-based nonionic surfactant. This is in agreement with the general behavior of polyelectrolyte-surfactant systems. LS as emulsifier in oil/water emulsions (o/w) gives rapid creaming into a highly concentrated emulsion, which is stable towards coalescence. The addition of cationic surfactant enhances the stability towards creaming. LS is a poor foaming agent, but the addition of cationic surfactant greatly improves the foam stability.

Interactions between cationic starch and anionic surfactants 2. Viscosity and aggregate size in dilute solutions

Abstract The effects of the charge density of the polymer, the chain length of the surfactant and the ionic strength on the viscosity and particle size of cationic starch/surfactant/water systems were investigated. Critical association concentrations (CAC) were observed at concentrations well below the CMCs of the surfactants. A strong decrease in the viscosity at concentrations just below the phase separation concentrations is observed. Associative phase separation occurs in extremely dilute systems when the charge ratio between the surfactants and the polymers is about one. The separated phase is a highly viscous gel phase containing less than 60% water. Depending on the charge density, the gel dissolves entirely or partly when excess surfactant is added. The properties of the systems can be understood qualitatively assuming that (1) formation of surface active complexes through ion condensation occurs in very dilute solutions, (2) the driving force of association of the surfactants with the polysaccharide chains increases as the hydrophobic chain length of the surfactant or the charge density of the polyelectrolyte increases, and (3) there is an associative interaction between the surfactant aggregates and the polysaccharide which decreases with increasing ionic strength.

Interactions between cationic starch and anionic surfactants. III. Rheology and structure of the complex phase

Abstract This paper reports on studies of the rheological properties of cationic starch (CS)/ surfactant systems. The degree of substitution of the CS was 0.1 - 0.8. Surfactants investigated were sodium dodecyl sulfate (SDS), potassium octanoate (KOct), sodium decanoate (NaDe)potassium dodecanoate (KDod), sodium oleate (NaOl) and sodium erucate (NaEr). Aggregation of surfactant micelles with the polymer produces a hydrophobic and pseudoplastic gel-like complex phase with low water content and high viscosity. The rheological behavior of the gels is described by the Herschel-Bulkley model. In dilute aqueous solution the CS/surfactant aggregate structure resembles a randomly coiled polymer network, in which polymer molecules are linked by micelles. The rheological data for the gel are compatible with the assumption that the surfactants form liquid crystalline structures with the polymer anchored to the surfactant aggregates, as recently suggested for analogous systems. However, this conjecture needs to be co...