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Time-resolved SAXS study of the effect of a double hydrophilic block-copolymer on the formation of CaCO<sub>3</sub> from a supersaturated salt solution

Time-resolved SAXS study of the effect of a double hydrophilic block-copolymer on the formation of CaCO3 from a supersaturated salt solution

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BOLZE, Jörg, Diego PONTONI, Matthias BALLAUFF, Theyencheri NARAYANAN, Helmut CÖLFEN, 2004. Time-resolved SAXS study of the effect of a double hydrophilic block-copolymer on the formation of CaCO3 from a supersaturated salt solution. In: Journal of Colloid and Interface Science. 277(1), pp. 84-94. ISSN 0021-9797. eISSN 1095-7103. Available under: doi: 10.1016/j.jcis.2004.04.029

@article{Bolze2004-09Timer-40380, title={Time-resolved SAXS study of the effect of a double hydrophilic block-copolymer on the formation of CaCO3 from a supersaturated salt solution}, year={2004}, doi={10.1016/j.jcis.2004.04.029}, number={1}, volume={277}, issn={0021-9797}, journal={Journal of Colloid and Interface Science}, pages={84--94}, author={Bolze, Jörg and Pontoni, Diego and Ballauff, Matthias and Narayanan, Theyencheri and Cölfen, Helmut} }

Pontoni, Diego 2017-10-18T09:42:19Z Bolze, Jörg Time-resolved SAXS study of the effect of a double hydrophilic block-copolymer on the formation of CaCO<sub>3</sub> from a supersaturated salt solution 2017-10-18T09:42:19Z The effect of a double hydrophilic block-copolymer additive (made of polyaspartic acid and polyethyleneglycol, pAsp(10)-b-PEG(110)) on the initial formation of calcium carbonate from a supersaturated salt solution has been studied in situ by means of time-resolved synchrotron small-angle X-ray scattering (SAXS). A stopped-flow cell was used for rapidly mixing the 20 mM aqueous reactant solutions of calcium chloride and sodium carbonate. In reference measurements without polymer additive the very rapid formation of primary, overall spherical CaCO<sub>3</sub> particles with a radius of ca. 19 nm and a size polydispersity of ca. 26% was observed within the first 10 ms after mixing. A subsequent, very rapid aggregation of these primary particles was evidenced by a distinct upturn of the SAXS intensity at smallest angles. During the aggregation process the size of the primary particles remained unchanged. From an analysis of the absolute scattering intensity the mass density of these particles was determined to 1.9 g/cm<sup>3</sup>. From this rather low density it is concluded that those precursor particles are amorphous, which has been confirmed by simultaneous wide-angle X-ray diffraction measurements. Upon adding 200 pm of the block-copolymer no influence on the size, the size polydispersity and morphology of the primary particles, nor on the kinetics of their formation and growth, was found. On the other hand, the subsequent aggregation and precipitation process is considerably slowed down by the additive and smaller aggregates result. The crystalline morphology of the sediment was studied in situ by WAXS ca. 50 min after mixing the reactants. Several diffraction rings could be detected, which indicate that a transformation of the metastable, amorphous precursor particles to randomly oriented vaterite nanocrystallites has taken place. In addition, a few isolated Bragg spots of high intensity were detected, which are attributed to individual, oriented calcite microcrystals that nucleated at the wall of the capillary. Ballauff, Matthias Pontoni, Diego Narayanan, Theyencheri Ballauff, Matthias Cölfen, Helmut Bolze, Jörg Narayanan, Theyencheri 2004-09 eng Cölfen, Helmut

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