MORPHOLOGY OF COMPLEX AGGREGATES IN SHAMPOOS 295 STRUCTURE OF THE POLYMER CHAIN AND THE MORPHOLOGY OF THE PRECIPITATED COMPLEX The relationship between the structure of the polymer chains and the morphology of the precipitated complexes was investigated. When compared with CC molecules in which Figure 6. Effect of LPB mixing on the morphology of precipitated complexes from ten-times-diluted model shampoo solution. Figure 7. Effect of C18E25 mixing on the morphology of precipitated complexes from ten-times-diluted model shampoo solution.
JOURNAL OF COSMETIC SCIENCE 296 glucose units are connected by β-1,4 bonds, CD molecules in which glucose units are connected through α-1,6 bonds have a higher bendability. Figure 8 shows the partial phase diagrams of the systems containing CD at α = 0.38 and LES/LPB. The CP region for the system containing LES alone lay on the low surfactant concentration side of the diagram (Figure 11a), and it widened on the low salt concentration side when LPB was added to the system, bringing the composition of the diluted model shampoo solution into the CP region. The same trend was observed for the system containing less cation- ized CD at α = 0.30. A comparison of the phase diagrams in Figure 8 with those for the systems containing CC at α=0.38 (Figure 4a–c) revealed that no complex precipitation occurred in the dilution of the systems containing CD when the charge on the surfactant micelles was high. LPB mixing with CD at α = 0.38 tended to widen the CP region on the lower salt concentration side, and the complexes coacervated in dilution (Figure 8b,c). Figure 9a,b shows typical SEM images of complexes precipitated in the dilution process of the model shampoo solutions containing LES/LPB=3/1 and CD at α=0.38, 0.30. Membranous aggregates of the complexes precipitated in both cases independently of the charge on CD. MECHANISM OF THE MORPHOLOGY FORMATION OF THE COMPLEX AGGREGATES The morphology of the complexes precipitated in the model shampoo solution changed according to the degree of cationic charge, the structure of the polymer chains, and the composition of the surfactant mixtures. The dilution of the model shampoo solution is likely to cause changes in the dissolved state of the complexes before the composition reaches the CP region. Figure 10 shows the changes in the relative scattered light intensity, Figure 8. Partial phase diagrams for systems containing 0.1wt% CD at α=0.38, LES and LPB as surfactants, and Na2SO4 as salt at varied concentrations. The region above the dotted line was not observed. Figure 9. Effect of CD bendability on the morphology of the precipitated complex from ten-times-diluted model shampoo. Surfactant: LES/LPB=3/1.
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