Toughening of epoxy thermosets by self-assembled nanostructures of amphiphilic comb-like random copolymers.

Amphiphilic comb-like random copolymers synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMMA) and stearyl methacrylate (SMA) with PEGMMA contents ranging between 30 wt% and 25 wt% were demonstrated to self-assemble into various well-defined nanostructures, including spherical micelles, wormlike micelles, and vesicle-like nanodomains, in anhydride-cured epoxy thermosets. In addition, the polymer blends of the comb-like random copolymer and poly(stearyl methacrylate) were prepared and incorporated into epoxy thermosets to form irregularly shaped nanodomains. Our research findings indicate that both the comb-like random copolymers and polymer blends are suitable as toughening modifiers for epoxy. When added at a concentration of 5 wt%, both types of modifiers lead to substantial improvements in the tensile toughness (>289%) and fracture toughness of epoxy thermosets, with minor reductions in their elastic modulus (<16%) and glass transition temperature (<6.1 °C). The fracture toughness evaluated in terms of the critical stress intensity factor (KIC) and the strain energy release rate (GIC) increased by more than 67% and 131% for the modified epoxy thermosets containing comb-like random copolymers.

The fabrication of polycrystalline silver nanowires via self-assembled nanotubes at controlled temperature.

We report a novel method for the fabrication of silver nanowires under controlled conditions. Silver nanoparticles were synthesized using a surfactant of octanoic acid via a reverse micelle technique. Hollow nanotubes were prepared under various controlled conditions through self-assembly of surfactant clusters of reversed micelles containing silver nanoparticles. These organized nanotubes were used as a structure-directing template for the preparation of silver nanowires. This is a bottom-up technique for the fabrication of silver nanowires. Self-assembled nanotube construction and the cross section of the nanotubes were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. From the results, reasonable schematic representations of the formation of self-assembled nanoparticles and nanowires were proposed. Further sintering treatment at 500 degrees C burned away the organic compounds and left silver nanowires. The construction of the nanowires was confirmed using SEM, x-ray diffraction (XRD), and energy dispersive x-ray analysis (EDXA). This paper demonstrates that silver nanowires can be fabricated via self-assembled nanoparticles at a controlled low temperature.

Degradation of phenol and TCE using suspended and chitosan-bead immobilized Pseudomonas putida.

The degradability of phenol and trichloroethene (TCE) by Pseudomonas putida BCRC 14349 in both suspended culture and immobilized culture systems are investigated. Chitosan beads at a size of about 1-2mm were employed to encapsulate the P. putida cells, becoming an immobilized culture system. The phenol concentration was controlled at 100 mg/L, and that of TCE was studied from 0.2 to 20 mg/L. The pH, between 6.7 and 10, did not affect the degradation of either phenol or TCE in the suspended culture system. However, it was found to be an important factor in the immobilized culture system in which the only significant degradation was observed at pH >8. This may be linked to the surface properties of the chitosan beads and its influence on the activity of the bacteria. The transfer yield of TCE on a phenol basis was almost the same for the suspended and immobilized cultures (0.032 mg TCE/mg phenol), except that these yields occurred at different TCE concentrations. The transfer yield at a higher TCE concentration for the immobilized system suggested that the cells immobilized in carriers can be protected from harsh environmental conditions. For kinetic rate interpretation, the Monod equation was employed to describe the degradation rates of phenol, while the Haldane's equation was used for TCE degradation. Based on the kinetic parameters obtained from the two equations, the rate for the immobilized culture systems was only about 1/6 to that of the suspended culture system for phenol degradation, and was about 1/2 for TCE degradation. The slower kinetics observed for the immobilized culture systems was probably due to the slow diffusion of substrate molecules into the beads. However, compared with the suspended cultures, the immobilized cultures may tolerate a higher TCE concentration as much less inhibition was observed and the transfer yield occurred at a higher TCE concentration.