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Highly conductive nanofibers with 1570 S/m were obtained from an electrospun solution of polymer containing multiwalled carbon nanotubes (MWCNTs). Homogeneous dispersion of high concentrations of MWCNTs was achieved by attaching poly(styrenesulfonic acid graft aniline) (PSS-g-ANI), an amphiphilic surfactant, to the MWCNT surface. The hydrophilic sulfonic acid group facilitated the dissolution of PSS-g-ANI-grafted MWCNTs in a polyethylene oxide (PEO) solution up to 6.7 wt% MWCNT. To our knowledge, this is the highest level of MWCNT doping attained in a solution designed for electrospinning. With the incorporation of PSS-g-ANI, the concentration of MWCNTs embedded in the electrospun nanofibers increased. More importantly, the alignment of MWCNTs along the nanofiber axis increased significantly, as confirmed by observed birefringence under crossed polarizers. The combination of higher doping levels and better alignment afforded highly conductive nanofibers suitable for electronic nanodevices.

The interfacial fracture toughness between semi-crystalline polymers (polyamide/polypropylene) were studied to understand the failure mechanisms at the interface, especially when the interface was reinforced by an in situ compatibilizer. Based on the observation of the interface using scanning electron microscopy and wide angle X-ray spectroscopy, it was revealed that crystalline structure of polypropylene was not affected by the in situ compatibilizer at the interface. The reinforcing mechanism could be qualitatively identified by investigating the evolution of fracture toughness as a function of annealing time and temperature. The adhesion strength increased with the annealing time. Depending on the annealing temperature, the fracture toughness passed a peak value and then reached a plateau after some bonding time. As long as the chain length of the compatibilizer is long enough to form entanglements with the molecules at both bulk sides, the fracture at the interface is decided by the balance between adhesion strength at the interface and cohesive strength in the weak modulus side; the failure locus follows the lower one. Thus, adhesive failure occurred first when the reaction at the interface did not occur long enough to provide high adhesive strength at the interface, but the cohesive failure occurred in the crack propagation side after the adhesive strength value became higher than the cohesive strength value.

The surface area change of UHMWPE fibers which underwent oxygen plasma treatment was measured as a function of plasma power and plasma treatment time. The interfacial adhesion of oxygen plasma treated UHMWPE fibers was evaluated via micro-droplet test and double cantilever beam test Surface area increased with plasma treatment time at 30 and 60W, but showed a maximum at 100 and 150W. The interfacial adhesion of UHMWPE fibers to vinylester resin exhibited the same trend as the surface area. SEM analysis revealed that oxygen plasma treatment roughened UHMWPE fibers by forming micro-pores leading to increased surface area. However, 1S0W plasma treatment led to degradation of the fibers and thus resulted in failure within the fiber surface layers, producing ribbon-like strips of fiber.

With the aid of a technique that induces electric-field-generated capillary waves on a polymeric liquid surface and the resulting wave propagation characteristics detected by an optical diffraction method, we examined the behavior of a diblock copolymer (poly(dimethylsiloxane-b-ethylene oxide)) at the interface between two oligomeric ethers, low molecular weight poly(dimethylsiloxane) (PDMS) and poly(ethylene glycol) (PEG). The interfacial tension values in the presence of the diblock copolymer at the interface were obtained from the dispersion equation. Upon addition of increasing amounts of the copolymer, the interfacial tension dropped rapidly and leveled off as the concentration surpassed some value. The reduction in the interfacial tension with an increasing amount of the block copolymer calculated by a self-consistent mean-field (SCMF) model showed good agreement with the experimental data, quantitatively as well as qualitatively. The SCMF calculations predicted that the effects of the copolymer on the interfacial properties in the strong segregation regime were governed by the structure of the copolymer (not only by the degree of polymerization of both the longer block and the short block but also by their relative length ratio) as well as by the degree of polymerization of the homopolymers. Depending on the relative length ratio between the two blocks, micelle formation competed with surface segregation of the block copolymer molecules.