Mihaela Olaru

Effect of SO2 Dry Deposition on Porous Dolomitic Limestones

The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100) and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA) were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units.

Silsesquioxane-based Hybrid Nanocomposite with Self-assembling Properties for Porous Limestones Conservation

The study was concerned with the synthesis and characterization of a silsesquioxane-based hybrid nanocomposite with self-assembling properties intended for monumental porous limestone conservation. Radical polymerization of 3-(trimethoxysilyl)propyl methacrylate in the presence of a primary amine surfactant yielded a new type of hybrid nanocomposite, in which silica was dispersed as domains with typical sizes in the nanometer range. The self-assembling properties of the synthesized composite have been ascribed to the supramolecular assembling abilities of the surfactant, as well as to the combination of linear, ladder, and cage-like fragments of silsesquioxane type. This new sol—gel approach, in which the surfactant makes the pore size of the network more coarse and uniform, avoids cracking while drying inside the stone and thus provides an effective alternative for porous limestone conservation.

Functional silsesquioxane-based hierarchical assemblies for antibacterial/antifungal coatings

This paper reports the first study on functional silsesquioxane-based hierarchical assemblies containing an ordered distribution of silver nanoparticles with a large number of {111} facets, obtained through sol-gel reaction, intended for antibacterial/antifungal coatings.

Silsesquioxane-Based Hybrid Nanocomposites of Polymethacrylate Type with Self-Assembling Properties

The aim of the study was to synthesize and characterize silsesquioxane-based hybrid nanocomposites with self-assembling properties to be used in monumental stone conservation. Through radical polymerization of 3-(trimethoxysilyl)propyl methacrylate, a monomer that contains both methacrylate and silica phases, in the presence of a primary amine surfactant, at different silica precursor:ethanol molar ratios, new types of hybrid nanocomposites, in which silica was dispersed as domains with typical sizes in the nanometer range, were obtained. The self-assembling properties of the synthesized composites have been ascribed to the supramolecular assembling abilities of the surfactants, as well as to the combination of linear, ladder, and cagelike fragments of silsesquioxane type. The incorporation of surfactant within the sol-gel derived matrix may also lead to the obtaining of compounds that avoid cracking of the hybrid gel while drying inside the stone.

Siloxane-based polymers as protective coatings against SO2 dry deposition

The present research was focused on investigating the ability of different siloxane-based polymeric coatings to provide environmental protection to monumental limestone (Repedea from Romania) used in the north-eastern part of Romania for the construction of many stone monuments. Three siloxane-based polymers used throughout the world in protecting stone monuments, namely Lotexan-N, Silres® BS 290 and Tegosivin HL 100 and a newly designed hybrid nanocomposite containing silsesquioxane units (TMSPMA) were selected as polymeric coatings. The ability of the coatings to protect the stone from dry SO2 deposition in the presence of humidity in a standardized accelerated ageing test was determined. A comparative study of the obtained results indicates that the stone samples treated with the new hybrid siloxane-based nanocomposite exhibited improved resistance to degradation after being exposed to a SO2 saturated atmosphere.

PVA-based hybrid composites with luminescent properties for drug delivery

The aim of this study was to synthesize and characterize new poly(vinyl alcohol)s (PVAs) hybrid composites with or without a basic drug content, e.g., 2-[4-(2-methylpropyl)phenyl]propanoic acid (ibuprofen), obtained at different pH values. Through sol-gel approach of chloropropyltriethoxysilane with a PVA precursor containing a fluorescent dye (lissamine rhodamine-B sulfonyl chloride), new hybrid materials with porous structures were obtained. Due to encapsulation in a porous network, the influence of rhodamine H-dimers on fluorescence quenching was negligible and the presence of free dye was exploited as a mechanism for anchoring the ibuprofen molecules through hydrogen bonding onto pore surfaces.