Study on the synthesis of spherulitic calcium carbonate composite in amphiphilic PS-b-PAA solution and its crystalline structure

摘要

Spherulitic calcium carbonate composite is synthesized in the solution of amphiphilic block copolymer PS-b-PAA. FE-SEM and XRD measurements show that the size of the particulates decrease with the augment of PS-b-PAA concentration, and the morphology as well as the crystalline structure* are changed too. TG-DTA together with IR analysis is applied to investigate the thermal dynamic behavior of the composite. The results show that the composite is mainly composed of two phases, that is, the nanocrystalline calcium carbonate and the PS-b-PA-Ca composites. In DTA curves, PS phase decomposes first with a large heat release at the temperature range between 300 and 400 deg C. However, the PAA chains have relatively higher thermal stability, probably due to the structural Ca-O bond, and decompose between 400 and 500 deg C. The above studies on the morphology and crystal structure of the calcium carbonate and the thermal stability indicate that the micellization of amphiphilic block copolymers, the stretching of ionized PAA chains and the preferential induction of neighboring carboxyl group on the precipitation of calcium carbonate may cause the formation of the spherulitic composite.