The crystallization characteristics of CaCO3 microparticles from supersaturate aqueous solutions in the presence of a conjugate drug-copolymer has been investigated, comparative with particles prepared in similar conditions but without polymer. The polymer conjugate, P(NVP-MA-Ox), is based on poly(N-vinylpyrrolidone-co-maleic anhydride) as support and 2-amino-5-(4-methoxy-phenyl)-1,3,4-oxadiazole. The influence of the polymer/CaCO3 ratio on the microparticles' characteristics and the particles' pH stability was deeply investigated by scanning electron microscopy, X-ray diffraction, flow particle image analysis, particles charge density, and electrophoresis. The presence of P(NVP-MA-Ox) as a template in the CaCO3 crystallization process induced the particles stability increase up to the polymer isoelectric point located at pH = 3.4, irrespective of carbonate content in composite particles. The adsorption capacity of the microparticles as a function of their characteristics was tested using methylene blue. The sorption capacity of composite materials increased with the increase of polymer content in the composites, suggesting that the sorption process takes place mainly by electrostatic interactions.

Polyelectrolyte multilayers are versatile materials that are used in a large number of domains, including biomedical and environmental applications. The fabrication of polyelectrolyte multilayers using the layer-by-layer technique is one of the simplest methods to obtain composite functional materials. The properties of the final material can be easily tuned by changing the deposition conditions and the used building blocks. This review presents the main characteristics of polyelectrolyte multilayers, the fabrication methods currently used, and the factors influencing the layer-by-layer assembly of polyelectrolytes. The last section of this paper presents some of the most important applications of polyelectrolyte multilayers, with a special focus on biomedical and environmental applications.

Polyelectrolyte complex (PEC) dispersions were prepared by controlled mixing of three random copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) [P(AMPS54-co-TBA46) and P(AMPS37-co-TBA63)] or methyl methacrylate (MM) [P(AMPS52-co-MM48)] with an ionene-type polycation, containing 95 mol % N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units (PCA5), with their structural characteristics being deeply investigated by dynamic light scattering (DLS) and atomic force microscopy (AFM). Shape, size, and polydispersity of the PEC dispersions were directly observed by AFM as a function of polyanion structure, the ratio between charges, n-/n+, and the titrant addition rate (TAR). The particle sizes increased and the colloidal stability decreased with the increase of the nonionic comonomer content and with the decrease of TAR. It was demonstrated that the medium particle sizes of the complex nanoparticles adsorbed on silicon wafers measured by AFM, in the dry state, were close but always lower than those measured by DLS, both before and after the complex stoichiometry.

A new type of Cu(II) ion sorbents is presented. These are obtained by CaCO3 mineralization from supersaturated solutions on gel-like cross-linked polymeric beads as insoluble templates. A divinylbenzene-ethylacrylate-acrylonitrile cross-linked copolymer functionalized with weakly acidic, basic, or amphoteric functional groups has been used, as well as different initial inorganic concentrations and addition procedures for CaCO3 crystal growth. The morphology of the new composites was investigated by SEM and compared to that of the unmodified beads, and the polymorph content was established by X-ray diffraction. The beads, before and after CaCO3 mineralization, were tested as sorbents for Cu(II) ions. The newly formed patterns on the bead surface after Cu(II) sorption were observed by SEM, and the elemental distribution on the composites and the chemical structure of crystals after interaction with Cu(II) were investigated by EDAX elemental mapping and by FTIR-ATR spectroscopy, respectively. The sorption capacity increased significantly after CaCO3 crystals growth on the weak anionic bead surface (up to 1041.5 mg Cu(II) /g sample) compared to that of unmodified beads (491.5 mg Cu(II) /g sample).

No abstract

Composite solid surfaces with high content of functional groups (FGs) are useful materials in different types of applications requiring stimuli-responsive “hard/soft” architectures, their improved properties rising from the combination of organic–inorganic parts. Among different types of weak polyelectrolytes, poly­(ethyleneimine) (PEI) is of great interest in the construction of composite systems with thin layer-by-layer (LbL) organic films due to the large number of amino groups per unit mass of polymer. Herein, the spherical silica microparticles were modified with linear (L) or branched (B) PEI chains using LbL deposition of a copper complex (PEIL–Cu2+ or PEIB–Cu2+) and poly­(acrylic acid) (PAA), glutaraldehyde selective cross-linking, followed by copper and PAA extraction from the multilayer. The newly formed silica/(PEIL)10 and silica/(PEIB)10 composites were used in batch and column sorption/desorption experiments of four heavy metal ions (Cu2+, Ni2+, Co2+, and Cd2+). In noncompetitive conditions ([FG]/Σ­[M2+] > 9), all heavy metal ions were retained on composites, demonstrating the potential application of the prepared functional microparticles in surface water treatment. However, in competitive conditions ([FG]/Σ­[M2+] < 9), only Cu2+ is sorbed in high amount (∼2.5 mmol·g–1 PEI) on composites, with simultaneous displacement of already sorbed ions, demonstrating the solid-phase extraction and chromatographic properties of the synthesized silica/(PEIL) n and silica/(PEIB) n composites.

This study describes the effects of mixed anionic/ cationic polyelectrolytes on the crystallization of calcium carbonate in supersaturated solutions in comparison with polyanion-based CaCO 3 composite structures. Two simple methods of introducing the polycation in the crystallogenesis of calcium carbonate are proposed: preformed nonstoichiometric polyelectrolyte complexes (NPECs) or in situ mixing of complementary polyelectrolytes, with a very large range of ratios between complementary polyions. For this purpose three polyanionspoly(acrylic acid) sodium salt, poly(sodium 4styrenesulfonate) and poly(sodium vinylsulfonate)and poly-(diallyl-dimethylammonium chloride) as polycation were used. The molar ratio between complementary polyelectrolytes used in CaCO 3 composite synthesis varied between 0 (just polyanions) up to 0.95 (close to the equimolar ratio between ionic charges of complementary polyelectrolytes). The polymer presence into the composite particles, as a function of polyanion structure and the preparation mode, was evidenced by energy dispersive X-ray diffraction and particle charge detection in the supernatant fraction. Scanning electron microscopy was used to provide the particles' morphology, and Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy was used to determine the polymorph content ratio. The enhanced CaCO 3 / polyanion/polycation microparticles stability in ethylenediamine tetraacetic acid has been also shown compared to CaCO 3 / polyanion microparticles as a function of the molar ratio between complementary polyelectrolytes and the method of introducing the polycation in the crystallogenesis system.

New types of composites were obtained by an autotemplate method for assembling hollow CaCO 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/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.