Polyurethane/organically modified montmorillonite (PU/O‐MMT) nanocomposites were electrospun and the effect of O‐MMT on the morphology and physical properties of the PU/O‐MMT nanofiber mats were investigated for the first time. The average diameters of the PU/O‐MMT nanofibers were ranged from 150 to 410 nm. The conductivities of the PU/O‐MMT solutions were linearly increased with increasing the content of O‐MMT, which caused a decrease in the average diameters of the PU/O‐MMT nanofibers. The as‐electrospun PU and PU/O‐MMT nanofibers were not microphase separated. The exfoliated MMT layers were well distributed within the PU/O‐MMT nanofibers and oriented along the fiber axis. When the PU/O‐MMT nanofibers were annealed, the exfoliated MMT layers hindered the microphase separation of the PU. The electrospinning of PU/O‐MMT nanocomposites resulted in PU nanofiber mats with improved Young's modulus and tensile strength. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3171–3177, 2005

In this study, montmorillonite (MMT)/poly (e-caprolactone)-based polyurethane cationomer (MMT/ PCL-PUC) nanocomposites were prepared and their mechanical properties, thermal stability, and biodegradability were investigated. PCL-PUC has 3 mol % of quaternary ammonium groups in the main chain. The MMT was successfully exfoliated and well dispersed in the PCL-PUC matrix for up to 7 wt % of MMT. The 3 mol % of quaternary ammonium groups facilitated exfoliation of MMT. The 1 wt % MMT/PCL-PUC nanocomposites showed enhanced tensile properties relative to the pure PCL-PU. As the MMT content increased in the MMT/PCL-PUC nanocomposites, the degree of microphase separation of PCL-PUC decreased because of the strong interactions between the PCL-PUC chains and the exfoliated MMT layers. This resulted in an increase in the Young's modulus and a decrease in the elongation at break and maximum stress of the MMT/PCL-PUC nanocomposites. Biodegradability of the MMT/PCL-PUC nanocomposites was dramatically increased with increasing content of MMT, likely because of the less phaseseparated morphology of MMT/PCL-PUC.

SYNOPSISPoly( ether urethane) ( P E U ) prepolymer terminated with isocyanate at both ends was prepared by controlling the mol ratio of poly (tetramethylene glycol) and methane diphenyl-4,4'-diisocyanate. Using this prepolymer as an activator, the anionic polymerization of ccaprolactam was carried out to obtain PEU-nylon 6 block copolymer. The phase structure of the block copolymers was characterized on the basis of molecular interaction. The results of dynamic mechanical and thermal analyses revealed that the block copolymer films prepared via melt pressing and subsequent quenching had a one-phase structure. The equilibrium melting temperatures determined by a Hoffman-Weeks plot showed that the two blocks are miscible in the melt state. N-Trifluoroacetylation of the block copolymer led to the conclusion that this miscible behavior is due mainly to the specific interaction between urethane groups in PEU block and amide groups in nylon 6 block through hydrogen bonding.

Nanocomposites based on thermoplastic elastomeric polyurethane (TPU) and layered silicate clay were prepared by in situ synthesis. The properties of nanocomposites of TPU with unmodified clay were compared with that of organically modified clay. The nanocomposites of the TPU and organomodified clay showed better dispersion and exhibited superior properties. Exfoliation of the clay layers was observed at low organoclay contents, whereas an intercalated morphology was observed at higher clay contents. As one of major purposes of this study, the effect of the silicate layers in the nanocomposites on the order-disorder transition temperature (T ODT ) of the TPU was evaluated from the intensity change of the hydrogen-bonded and free carbonyl stretching peaks and from the peak position change of the NÀ ÀH bending peak. The presence of the organoclay increased T ODT by approximately 108C, which indicated improved stability in the phase-separated domain structure. The layered silicate clay caused a tremendous improvement in the stiffness of the TPU; meanwhile, a reduction in the ultimate elongation was observed.

An OTDM multihop prototype network, developed at Princeton University, is presented. By employing a new self-routing scheme with special address coding suitable for optical packet switching, 100Gbit/s optical packet switching in an 8-node transparent shuffle network is demonstrated offering extremely high bandwidth and low latency