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Effects of (complementary) polyelectrolytes characteristics on composite calcium carbonate microparticles properties
This study follows the possibility to tune the thermal stability of some CaCO3/polymer composites by crystal growth from supersaturated solutions controlled by polymer structure or by using nonstoichiometric polyelectrolyte complexes (NPECs). As the ratio between the organic and inorganic parts in the composites controls the Ca2+/polymer network crosslinking density, the CaCO3/polymer weight ratio was kept constant at 50/1, varying the initial concentration of the polyanions solutions (0.05 or 0.06 wt.%), the NPECs molar ratio , n+/n- (0.2 or 0.4), or the inorganic precursors concentration (0.25 or 0.3 M). Poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid) (PSA) and chondroitin-4-sulfate (CSA) were used as polyanions. Some NPEC dispersions, prepared with the same polyanions and poly(allylamine hydrochloride) (PAH), were also used for calcium carbonate crystallization. The characteristics of the prepared composites were investigated by scanning electron microscopy (SEM), flow particle image analysis (FPIA), particles charge density (CD), zeta-potential (ZP). The thermal stability of the composite particles was investigated as compared to bare CaCO3 microparticles prepared at the same initial inorganic concentrations
Autotemplate Microcapsules of CaCO<sub>3</sub>/Pectin and Nonstoichiometric Complexes as Sustained Tetracycline Hydrochloride Delivery Carriers
New types of composites
were obtained by an autotemplate method for assembling hollow CaCO<sub>3</sub> capsules by using pH-sensitive polymers. Five pectin samples,
which differ in the methylation degree and/or amide content, and some
nonstoichiometric polyelectrolyte complex dispersions, prepared with
the pectin samples and poly(allylamine hydrochloride), were used to
control the crystal growth. The morphology of the composites was investigated
by scanning electron microscopy, and the polymorphs characteristics
were investigated by FTIR spectroscopy. The presence of the polymer
in the composite particles was evidenced by X-ray photoelectron spectroscopy,
particle charge density, and zeta-potential. The new CaCO<sub>3</sub>/pectin hollow capsules were tested as a possible matrix for a tetracycline
hydrochloride carrier. The kinetics of the drug release mechanism
was followed using Higuchi and Korsmeyer–Peppas mathematical
models