Nanocomposites and nanomaterials

Creation of polyelectrolyte films and capsules by layer-by-layer self-assembly
Guzenko N.V.1, Gabchak O.L.1, Pakhlov E.M.1, Skwarek E.2, Janusz W.2
1 Chuiko Institute of Surface Chemistry, NAS of Ukraine, 17 General Naumov Str., Kyiv 03164, Ukraine. E-mail: guznataliia@gmail.com
2 Faculty of Chemistry, Maria Curie-7 Skłodowska University, pl. Marii Curie-Skłodowskiej 3, 2-031 Lublin, Poland.

Method of layer-by-layer self-assembly of polyelectrolytes provides ample opportunities for creation of thin polymer films and capsules with precise control of their thickness, composition, morphology and chemical functionality. The process of interpolyelectrolyte complex (IPEC) formation has been carried out for the couple of oppositely charged polymers (polyhexamethylenguanidine hydrochloride, PHMG and sodium carboxymethylcellulose, CMC) by simple mixing in solution and by layer-by-layer adsorption on the piezo-quartz crystal and on the surface of micro-sized calcium carbonate spherical particles. 
An insoluble IPEC was synthesized by mixing equal volumes of aqueous solutions of PHMG and CMC. This indicates that a complete compensation of the charge of both polymers occurs in this case. The absorption bands characterizing the vibrations of CMC groups manifested themselves more intensively in IR spectra of the complex, whereas in the mechanical mixture of equal mass parts of the polymers, the intensity of the absorption bands of both polymers was comparable. This can indicate a mass predominance of CMC in the complex.
A step-by-step formation of stable, irreversibly adsorbed multilayer film of the polymers has been demonstrated using the quartz crystal microbalance method. After the adsorption of fourth double polyelectrolyte layers the vibration frequency reduction of quartz crystal resonator was 1000 Hz that corresponds to 0.05 g/m mass increase of the formed polymer film. Particles charge overcompensation after the layer-by-layer adsorption of PHMG and CMC on the surface of spherical particles of CaCO3 was observed using the electrophoresis method. Twenty cycles of polymer adsorption followed by the core dissolution in EDTA resulted in formation of hollow capsules with unusually thick shell (5 μm) stable in neutral medium. The mass of the multilayer shells was 13.6% of the core mass. The density of the shells, calculated based on microscopic and thermogravimetric data, amounted to 4104 g/m3, which indicates the formation of a loose polymer film in the conditions of synthesis. Moreover IR spectra of the polymer capsules show the absorbance bands, which were characteristic for the IPEC, obtained in solutions.