On the role of block copolymer additives for calcium carbonate crystallization:Small angle neutron scattering investigation by applying contrast variation

摘要

The role of the double-hydrophilic block copolymer poly(ethylen glycol)-block-poly(methacrylic acid) (PEG-b-PMAA) on the morphogenesis of calcium carbonate (CaCO_3) was studied by applying the contrast variation small angle neutron scattering technique.The morphology and size of CaCO_3 crystals is strongly affected by the addition of PEG-b-PMAA.In order to determine the partial scattering functions of the polymer and CaCO_3 mineral,we developed both an experimental and theoretical approach with a sophisticated method of their determination from the scattering intensity.Partial scattering functions give detailed information for each component.In particular,the partial scattering function of the polymer,S_(pp) ,shows a monotonic slope with Q~(-2 to -3) where the scattering vector Q is low (Q<0.01 A~(-1)),which is a clear evidence that the polymer within the CaCO_3 mineral has a mass fractal dimension.The other partial scattering functions reflected the geometry of the CaCO_3 particles or the "interaction" of polymer and CaCO_3 on a microscopic scale,which leads to a coherent view with S_(pp) .