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Peripheral nerve regeneration across long nerve gaps is clinically challenging. Autografts, the standard of therapy, are limited by availability and other complications. Here, using rigorous anatomical and functional measures, we report that aligned polymer fiber-based constructs present topographical cues that facilitate the regeneration of peripheral nerves across long nerve gaps. Significantly, aligned but not randomly oriented fibers elicit regeneration, establishing that topographical cues can influence endogenous nerve repair mechanisms in the absence of exogenous growth promoting proteins. Axons regenerated across a 17mm nerve gap, reinnervated muscles, and reformed neuromuscular junctions. Electrophysiological and behavioral analyses revealed that aligned, but not randomly oriented constructs facilitated both sensory and motor nerve regeneration, significantly improved functional outcomes. Additionally, a quantitative comparison of DRG outgrowth in vitro and nerve regeneration in vivo on aligned and randomly oriented fiber films clearly demonstrated the significant role of sub-micron scale topographical cues in stimulating endogenous nerve repair mechanisms.

Poly(vinyl alcohol) (PVA) composite films using poly(vinyl pyrrolidone) (PVP) and sodium dodecyl sulfate (SDS)-covered, well dispersed single wall carbon nanotubes (SWNT) exhibit significant improvement in tensile strength and modulus as compared to the control PVA and PVA/PVP/SDS films. The evidence of load transfer to the nanotubes in the composite film has been obtained from the shift in the Raman SWNT D* band peak position.

Carbon nanotubes (CNTs) are regarded as ideal filler materials for polymeric fiber reinforcement due to their exceptional mechanical properties and 1D cylindrical geometry (nanometer-size diameter and very high aspect ratio). The reported processing conditions and property improvements of CNT reinforced polymeric fiber are summarized in this review. Because of CNT polymer interaction, polymer chains in CNTs' vicinity (interphase) have been observed to have more compact packing, higher orientation, and better mechanical properties than bulk polymer. Evidences of the existence of interphase polymers in composite fibers, characterizations of their structures, and fiber properties are summarized and discussed. Implications of interphase phenomena on a broader field of fiber and polymer processing to make much stronger materials are now in the early stages of exploration. Beside improvements in tensile properties, the presence of CNTs in polymeric fibers strongly affects other properties, such as thermal stability, thermal transition temperature, fiber thermal shrinkage, chemical resistance, electrical conductivity, and thermal conductivity. This paper will be helpful to better understand the current status of polymer/CNT fibers, especially high-performance fibers, and to find the most suitable processing techniques and conditions.

Poly(p-phenylene benzobisoxazole) (PBO) has been synthesized in the presence of singlewall carbon nanotubes (SWNTs) in poly(phosphoric acid) (PPA) using typical PBO polymerization conditions. PBO and PBO/SWNT lyotropic liquid crystalline solutions in PPA have been spun into fibers using dry-jet wet spinning. The tensile strength of the PBO/SWNT fiber containing 10 wt % SWNTs is about 50% higher than that of the control PBO fibers containing no SWNTs. The structure and morphology of these fibers have been studied.

A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconducting SWNTs in the solubilized sample and predominantly metallic SWNTs in the residual solid sample according to Raman, near-IR absorption, and bulk conductivity characterizations.

An optically homogeneous solution/dispersion of single-wall carbon nanotubes (SWNTs) in oleum has been used to form isotropic films exhibiting fibrillar morphology. Tensile modulus, strength, and strain to failure of the film are 8 GPa, 30 MPa, and 0.5%, respectively. The electrical conductivity in the plane of the film is 1 × 105 S/m.

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