| 1. |
- Iselau, Frida, 1979, et al.
(författare)
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Competitive adsorption of amylopectin and amylose on cationic nanoparticles: a study on the aggregation mechanism
- 2016
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 12:14, s. 3388-3397
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigate the interactions between cationic nanoparticles and anionic starch, where the starch was composed of 20 wt% of amylose, a linear polymer, and 80 wt% of amylopectin, a branched polymer. The mechanism of aggregation was investigated by scattering techniques. It was found that the cationic particles formed large aggregates with the starch as a result of selective adsorption of the amylopectin. Amylose did not participate significantly in the aggregate formation even when the charge ratio of starch to particles was <1. For starch to particle ratio 41 stabilization was recovered mostly due to the large hindrance brought about by the highly branched amylopectin. This results in a shift of the stabilization mechanism from electrostatic to electrosteric. The internal structure of the aggregates was composed of primary particles with starch coils adsorbed on the surface. This information supports the proposed aggregation mechanism, which is based on adsorption of the negatively charged starch in patches on the positively charged nanoparticles causing attractive interaction between the particles.
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| 2. |
- Iselau, Frida, 1979, et al.
(författare)
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Formation and relaxation kinetics of starch-particle complexes
- 2016
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Ingår i: Soft Matter. - 1744-6848 .- 1744-683X. ; 12:47, s. 9509-9519
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Tidskriftsartikel (refereegranskat)abstract
- The formation and relaxation kinetics of starch-particle complexes were investigated in this study. The combination of cationic nanoparticles in suspension and anionic starch in solution gave rise to aggregate formation which was studied by dynamic light scattering, revealing the initial adsorption of the starch molecules on the particle surface. By examining the stability ratio, W, it was found that even in the most destabilized state, i.e. at charge neutralization, the starch chains had induced steric stabilization to the system. At higher particle and starch concentrations relaxation of the aggregates could be seen, as monitored by a decrease in turbidity with time. This relaxation was evaluated by fitting the data to the Kohlrausch-Williams-Watts function. It was found that irrespective of the starch to particle charge ratio the relaxation time was similar. Moreover, a molecular weight dependence on the relaxation time was found, as well as a more pronounced initial aggregated state for the higher molecular weight starch. This initial aggregate state could be due to bridging flocculation. With time, as the starch chains have relaxed into a final conformation on the particle surface, bridging will be less important and is gradually replaced by patches that will cause patchwise flocculation. After an equilibration time no molecular weight dependence on aggregation could be seen, which confirms the patchwise flocculation mechanism.
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