Forming crystalline polymer-nano interphase structures for high-modulus and high-tensile/strength composite fibers

PVA/single-walled nanotube (SWNT) composite fibers are fabricated using a steady shear-flow gel-spinning method. The resultant fibers show excellent tensile strength, modulus, and toughness of 4.9 GPa, 128 GPa, and 202 J·g^-1, respectively. Templated interfacial crystallization of PVA in the vicinity of SWNT is controlled by tailoring the degree of undercooling of PVA during the composite solution preparation. WAXD shows that the templated crystallization behavior of the PVA at the SWNT interfacial region is new. PVA/SWNT fibers that exhibit interfacial structure show a predominant crystallization plane of (001) as compared to the (101) plane seen in PVA/SWNT fibers without a distinct interfacial structure. This demonstrates that the PVA interfacial region around SWNT has denser crystalline chain-packing. Single-walled nanotubes (SWNTs) are used to template a new PVA crystalline interphase structure in shear-flow gel/spun composite fibers. The presence of the highly crystalline interphase regions provides improved contact between PVA chains and SWNT and a better stress transfer. The fibers show superior properties with tensile strength, modulus, and toughness of 4.9 GPa, 128 GPa, and 202 J·g^-1, respectively.