Cinzia De Vita

Rotational dynamics ESR investigation of the cholestane spin probe dissolved in a narrow dispersity poly(ethyl acrylate): effect of the presence of trace amounts of free monomer

The dynamics of cholestane spin probes dissolved in poly(ethyl acrylate) (PEA) matrices was fully investigated over a wide temperature range by means of ESR spectroscopy. A PEA sample with narrow molecular weight dispersion (PEA1) and a second one (PEA2) doped with about 2.7 wt.-% free ethyl acrylate were employed. Depending on temperature, different dynamical regimes were identified. The coupling between the spin probe dynamics and structural, β, and γ relaxation processes was recognised. At higher temperatures, Vogel-Fulcher laws well described the temperature dependence of the spin probe rotation, which tracks the backbone dynamics with different coupling degrees. The experiments provide the chance of evaluating the onset of cooperativity in the different PEA matrices. The information is obtained by comparing the temperature dependence of probe rotation with that of rheological measurements. Moreover, the dynamics of cholestane in PEA2 shows an Arrhenius regime in the highest temperature region, which exhibits a complete decoupling from the backbone dynamics. Cholestane spin probe.

Water-borne Organic and Hybrid Nanostructured Polymer Particles as Film-Forming Materials for the Consolidation and Protection of Porous Substrates.

A new class of materials consisting of water-borne formulations (lattices) of sub-micron to nano-sized heterophasic particles with film-forming capability has been developed. These lattices are prepared by either multi-step sequential emulsion polymerisation, as in the case of partially fluorinated acrylic lattices with core-shell particle structure, or by sequential emulsion copolymerisation of acrylates with the reactive comonomer TSPMA (trimethoxysilylpropyl methacrylate) followed by sol-gel co-condensation of various alkoxysilanes onto the pre-formed acrylic particles, yielding hybrid organic-inorganic core-shell particles. The investigation on the structure, morphology and chemical evolution of these systems during their synthesis and after film formation is aimed at optimizing their application properties in the field of the preservation of cultural property. In particular, the unique features resulting from the heterophasic nature of the latex particle can be directed towards the formation of partially fluorinated protective coatings with ultra-hydrophobic surfaces or of new consolidants for porous substrates based on nanostructured hybrid acrylic-organosiloxane materials.