Dispersion of reduced graphene oxide within thermoplastic starch/poly(lactic acid) blends investigated by small-angle X-ray scattering.

Reduced graphene oxide (rGO) was incorporated into plasticized cornstarch (TPS), poly(lactic acid) (PLA) and their blends. Small-angle X-ray scattering (SAXS) was used to investigate rGO dispersion within the materials. For the TPS/PLA blend at 70:30 composition, the incorporation of rGO led to a larger fraction of small-sized rGO sheets, which at 5.0 mass% content developed stable fractal structures and domains of correlated sheets. The formation of fractal structures resulted in substantial enhancements in macroscopic properties. For these hybrids, the electrical conductivity, melt viscosity, storage moduli and biodegradation rates presented enhancements in relation to the neat blend. For the TPS/PLA blend at 30:70 composition, SAXS results indicated the formation of smaller fractions of well-dispersed rGO sheets and of segregated larger rGO sheets. With rGO at 5 mass% content, less expressive increases in electrical conductivity, melt viscosity, storage moduli and biodegradation rates were observed.

Synthesis of Polypropylene/Organoclay Nanocomposites via In Situ Polymerization with Improved Thermal and Dynamic-Mechanical Properties.

Preparation of polypropylene/clay nanocomposites via in situ polymerization is investigated. MgCl2/organophilic clay bi-supported Ziegler-Natta catalysts were used to prepare these nanocomposites. Three organophilic clays (Cloisite 30B, Cloisite 15A, and Claytone HY) were used as support and reinforcement agents. The nanostructure of the composites was characterized by X-ray diffraction. The results showed that the most active catalyst was that with clay having high inter-layer spacing without functional OH groups. Moreover, the silica layers of the clays (Cloisite 15A and Claytone HY) in these polypropylene/clay nanocomposites were exfoliated and well dispersed in the polypropylene matrix. Differential scanning calorimetric was used to investigate both melting and crystallization temperatures, as well as the crystallinity of the nanocomposite samples. These results showed that Cloisite 15A and Claytone HY acted as nucleating agents in the process of crystallization of polypropylene. Thermogravimetric analysis showed that Cloisite 15A and Claytone HY promoted an increase in resistance to thermal degradation. Dynamic-mechanical analysis showed that nanocomposites presented an increase in the storage modulus. Furthermore, Cloisite 15A and Claytone HY promoted an increase in glass transition temperature. Small-angle X-ray scattering analysis was used to determine how clay and its concentration influence the size of the polymer nanocrystals.

New electrorheological fluid obtained from mercaptosilsesquioxane-modified silicate suspensions.

Ormosil based on mercaptosilsesquioxane-modified silicate (SiO2/SSQ-SH) particle was prepared by sol-gel process involving a co-condensation of the hydrolyzed 3-mercaptopropyl-trimethoxysilane (MPTMS) and tetraetoxysilane (TEOS). The resulting material was characterized by (29)Si solid nuclear magnetic resonance spectroscopy ((29)Si NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FEG-SEM) and small angle X-ray scattering (SAXS). The (SiO2/SSQ-SH) particle presents a hierarchical structure, extending from micro to nanoscale and consisting of three structural levels. This SiO2/SSQ-SH particle was used for the first time as the dispersed phase in silicone oil suspension to develop a new electro-rheological fluid with a very good response under the action of electrical field from 1 to 4 kV/mm, whose values are comparable to those exhibited by other conventional ER fluids, under the influence of electric field.

Characterization of nanostructured epoxy networks modified with isocyanate-terminated liquid polybutadiene.

Polybutadiene-block-epoxy prepolymer (DGEBA-b-PBNCO) copolymers with multi-branched topological structure were prepared by reacting isocyanate-multifunctionalized liquid polybutadiene (PBNCO) with DGEBA prepolymer and used to develop nanostructured rubber-modified epoxy thermosets cured with triethylene-tetramine (TETA) as the aliphatic amine. The nanoscopic structure was obtained with the addition of as high as 20 phr of rubber component and successfully demonstrated by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The glass transition temperature of the rubber-modified epoxy networks was slightly higher than the neat epoxy system. In addition, a unique combination of outstanding toughness and increased modulus and T(g) was achieved in these modified systems, which was attributed to the peculiar morphology associated with a strong interfacial adhesion imparted by the reaction between the isocyanate and hydroxyl groups present in the PBNCO and epoxy resin, respectively. The effect of the PBNCO on the gelation time of the epoxy/TETA system was investigated by rheological techniques. The NCO-functionalized polybutadiene decreased the gelation time, indicating an accelerating effect on the curing process, probably because of the urethane groups formed by the reaction between PBNCO and the epoxy resin during the PB-b-ER block copolymer preparation.

Immobilization of streptavidin in sol-gel films: Application on the diagnosis of hepatitis C virus.

Recent advances have accelerated the development of biosensors for the analysis of specific gene sequences. In this kind of biosensor, a DNA probe is immobilized on a transducer and the hybridization with the target DNA is monitored by suitable methodology. In the present work, the streptavidin (STA) was encapsulated in thin films siloxane-poly(propylene oxide) hybrids prepared by sol-gel method and deposited on the graphite electrode surface by dip-coating process. Biotinylated 18-mer probes were immobilized through STA and a novel amperometric DNA biosensor for the detection and genotyping of the hepatitis C virus (genotypes 1, 2A/C, 2B and 3) is described. The HCV RNA from serum was submitted to reverse transcriptase-linked polymerase chain reaction (RT-PCR) and biotin-labeled cDNA was obtained. Thus, the cDNA was hybridized to the target-specific oligonucleotide probe immobilized on the graphite electrode surface and following the avidin-peroxidase conjugate was added. The enzymatic response was investigated by constant potential amperometry at -0.45V versus Ag/AgCl using H(2)O(2) and KI solutions. HCV RNA negative and positive controls and positive samples of sera patients were analyzed and the results were compared to commercial kit. The proposed methodology appeared to be suitable and convenient tool for streptavidin immobilization and diagnose of HCV disease.