Gina-Gabriela Bumbu

Investigation of micromechanical cantilever sensors with microfocus grazing incidence small-angle X-ray scattering

Micromechanical cantilever arrays coated with polymer brushes are an alternative to traditional chemical sensors. A critical parameter for the sensor sensitivity is the coating quality, and small changes in the coating uniformity generate a different behavior of the sensors. Microfocus grazing incidence small-angle x-ray scattering proved to be a sensitive tool to characterize coating quality, enabling a structural and chemical coating analysis.

On the compatibility of polysaccharide/maleic copolymer blends I. Thermal behaviour of dextran containing blends

Abstract The compatibility of dextran (D) with maleic acid–vinyl acetate copolymer (MAc–VA) in the solid state as a thin film has been studied by coupling thermogravimetry and differential scanning calorimetry with infrared spectroscopy. Optical and electron microscopy have been also used to investigate the morphology of the blends. It has been established that blends with a content of dextran higher than 85 wt.% exhibit good compatibility, the morphology of the blends being a homogeneous fine particle dispersion, while blends with a prevalent MAc–VA copolymer content exhibit a tendency to phase separation.

Analysis and Characterization of Maleic Anhydride Copolymers. II. Some Aspects of Thermo-oxidative Decomposition

Abstract Six binary and ternary maleic anhydride copolymers with vinyl acetate, methyl meth-acrylate and styrene, useful as plastics, adhesives coatings, additives, etc., have been synthesized. Thermo-oxidative behavior under dynamic conditions of heating has been studied to test the possible changes during thermal treatments. The four or five thermo-oxidative steps of weight loss are characteristic for the studied copolymers. The characteristic temperatures, weight losses and overall kinetic parameters have been determined, and information about physical and/or chemical processes involved has been obtained.

A Facile Route to Reassemble Titania Nanoparticles Into Ordered Chain-like Networks on Substrate

A facile route to reassemble titania nanoparticles within the titania-block copolymer composite films has been developed. The titania nanoparticles templated by the amphiphilic block copolymer of poly(styrene)-block-poly (ethylene oxide) (PS-b-PEO) were frozen in the continuous PS matrix. Upon UV exposure, the PS matrix was partially degraded, allowing the titania nanoparticles to rearrange into chain-like networks exhibiting a closer packing. The local structures of the Titania chain-like networks were investigated by both AFM and SEM; the lateral structures and vertical structures of the films were studied by GISAXS and X-ray reflectivity respectively. Both the image analysis and X-ray scattering characterization prove the reassembly of the titania nanoparticles after UV exposure. The mechanism of the nanoparticle assembly is discussed.

Maleic copolymers with pendant disinfectant and/or odorant molecules. II. Thermal and thermo-oxidative behaviour

Abstract New esters of alternating maleic anhydride/styrene or vinyl acetate copolymers with thymol, eugenol, phenylethyl alcohol and citronellol, known as bioactive molecules with disinfectant and/or odorant properties, have been synthesized and characterized by conductometry and infrared spectroscopy. Their thermo-oxidative and thermal behaviour under dynamic conditions of heating were studied by means of thermogravimetry and differential scanning calorimetry. One or two thermogravimetric steps of weight loss are characteristic for the studied compounds in the 20–450°C temperature range, that are endothermic processes in DSC curves. The characteristic temperatures, weight losses, overall kinetic parameters and reaction heats were evaluated and information about physical and/or chemical processes involved, have been obtained. On the basis of these results two distinct pathways for the release of active moieties have been proposed in respect to the parent copolymer. IR spectra recorded after heating at various temperatures support the proposed mechanisms. ©

Analysis and Characterization of Maleic Copolymers—III. Differential Scanning Calorimetry Study

Abstract Endothermic physical processes and transition temperatures below 220°C of several binary and ternary copolymers of maleic anhydride with vinyl acetate, methyl methacry-late and/or styrene were studied by differential scanning calorimetry and infrared spectroscopy. To improve resolution of differential scanning calorimetry peaks and allow correct assignment of the chemical and physical processes in the studied temperature range, multiple heating-cooling or isothermal treatments were performed. The recycliza-tion of hydrolyzed maleic acid units to maleic anhydride units, occurring around 160–190°C, was confirmed by infrared spectra.