César Saldías

Thermal and morphological behavior of chitosan/PEO blends containing gold nanoparticles. Experimental and theoretical studies.

Using solution-casting method, binary blends of chitosan (CS) and poly (ethylene oxide) (PEO 100,000) containing Au nanoparticles (AuNPs) were prepared. Shifts in the melting temperature (Tm) and crystallization temperature (Tc) values for CS/PEO and CS/PEO/AuNPs blends were observed by calorimetric analysis. In general, CS/PEO/AuNPs blends tended to decompose at higher temperatures than neat polymers. From the FT-IR spectra, shifts in the main signals, such as -NH2, -OH and COC, were detected in the blends and were attributed to the polymer interactions and the incorporation of gold nanoparticles. In addition, the analysis of the blend topographies by atomic force microscopy (AFM) showed that at a higher CS content, more homogenous surfaces were observed. This behavior was attributed to the interactions present in the CS/PEO/AuNPs blends. Finally, theoretical analyses helped to confirm that the gold nanoparticles would be preferentially adsorbed onto the chitosan microdomains due to the interactions between acetyl and hydroxyl groups and Au atoms.

In situ preparation of film and hydrogel bio-nanocomposites of chitosan/fluorescein-copper with catalytic activity

Copper nanoparticles were introduced into chitosan/fluorescein (Ch/f) film and hydrogel matrices by immersion of the respective matrix into an aqueous solution containing the precursor metallic salt and further reduction in aqueous medium at 75°C for 3h under nitrogen (N2) atmosphere. TGA was used to estimate the metallic content of Ch/f-Cu film and hydrogel nanocomposites. The prepared nanocomposites were proven to be effective as catalytic materials in the reduction of methylene blue (MB) employing N2H4 as reducing agent. In addition, rate constants of the reduction reaction using Ch/f-Cu film and hydrogel nanocomposites as catalysts were determined. The experimental results showed that the catalytic activity and order of reaction of the MB-N2H4 reduction system depended strongly on the type of nanocomposite used. Finally, the recyclability of the film and hydrogel nanocomposites as catalytic materials was also studied.

Preparation of CuONPs@PVDF/Non-Woven Polyester Composite Membrane: Structural Influence of Nanoparticle Addition

Membrane distillation techniques appear as one of the most promise alternative to 15 guarantee the availability of potable water in time of scarce of this essential resource. For 16 membrane preparation, polyvinylidene fluoride (PVDF) is preferred due to the easier synthesis 17 procedures with respect to other fluorine based polymers. In this work, copper oxide nanoparticles 18 (CuONPs) at different weight percent (wt.%), embedded in PVDF membranes supported on 19 non-woven polyester fabric (NWPET) were prepared by the phase-inversion method, and 20 characterized by spectroscopy (ATR-FTIR, Raman) and electron microscopy techniques (SEM). The 21 PVDF deposited onto the NWPET was highly composed by its polar -phase (F( )= 53 %) which  22 was determined from the ATR-FTIR spectrum. The F( ) value was kept constant, in the whole  23 range of CuONPs studied (2-10 wt.%) as was determined from the ATR-FTIR spectrum. The 24 absence of signals corresponding to CuONPs in the ATR-FTIR spectra and the appearance of peaks 25 at 297, 360 and 630 cm-1 in the Raman spectra of the membranes suggested that the CuONPs are 26 preferably located in the inner of the membrane but not on its surface. The membrane 27 morphologies were characterized by SEM. From the obtained SEM micrographs, a decrease and 28 increase in the amount of micropores and nanopores, respectively, near to the surface and 29 intercalated in the finger-like layer were observed. As result of the CuONPs addition, the 30 nanopores in the sponge-like layer decrease in size. The values of water contact angle (WCA) 31 measurements showed a trend to decrease from 94° to 80° upon the addition of CuONPs (2-10 32 wt.%) indicating a diminish in the hydrophobicity degree of the membranes. Apparently, the 33 increase in the amount of nanopores near to the surface decreased the membrane roughness 34 becoming less hydrophobic. 35 36

Polyitaconates: a new family of “all polymer” dielectrics

This work presents the synthesis of new poly(itaconate)s containing sulfone or nitrile pendant groups through conventional radical polymerization together with their characterization and comparison with poly(methacrylate)s containing identical groups. Structural and thermal characterization has been carried out in terms of Fourier transform infrared spectroscopy, differential scanning calorimetry, nuclear magnetic resonance, and thermogravimetric analysis. Characterized by broad band dielectric spectroscopy (BDS), all polymers showed dielectric constant values between 7 and 10 (at 25 °C and 1 kHz) and relative low dielectric loss values (≈0.02). BDS measurements showed, for all the polymers analyzed, notorious subglass transitions even at temperatures below -100 °C, resulting in a broad temperature interval in which these polymers exhibit high dielectric constant and could work without high losses. Therefore, these materials seem to be good candidates for dielectric applications such as energy storage, among others.

Non-steroidal anti-inflamatory drugs as guest of dendronized polymeric nanocomposites

The study of dendronized polymeric nanocomposites like poly(diethylaminoethyl methacrylamide) (PEAM), poly(acryloil tris nitrile/(methylester)) (PATCN) and dendronized poly(e-caprolactone) as carriers of different non- steroidal antiinflamatory drugs like ibuprofen (IBU), ketoprofen (KTP), naproxen (NPX) and indomethacin (IMTh) are reported.