Polymer composite yarns containing a high loading of double-walled carbon nanotubes (DWNTs) have been developed in which the inherent acrylate-based organic coating on the surface of the DWNT bundles interacts strongly with poly(vinyl alcohol) (PVA) through an extensive hydrogen-bond network. This design takes advantage of a toughening mechanism seen in spider silk and collagen, which contain an abundance of hydrogen bonds that can break and reform, allowing for large deformation while maintaining structural stability. Similar to that observed in natural materials, unfolding of the polymeric matrix at large deformations increases ductility without sacrificing stiffness. As the PVA content in the composite increases, the stiffness and energy to failure of the composite also increases up to an optimal point, beyond which mechanical performance in tension decreases. Molecular dynamics (MD) simulations confirm this trend, showing the dominance of nonproductive hydrogen bonding between PVA molecules at high PVA contents, which lubricates the interface between DWNTs.

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Polymer-derived amorphous SiBCN ceramics are synthesized through a simple dehydrocoupling and hydroboration reaction of an oligosilazane containing amine and vinyl groups and BH3 3 Me 2 S, followed by pyrolysis. Two types of ceramics, denoted as Si 2 B 1 and Si 4 B 1 , are produced from preceramic polymers with Si/B ratios of 2/1 and 4/1, respectively. The structural evolution of these ceramics with respect to the pyrolysis temperature and boron concentration is investigated using solid-state NMR, Raman, and EPR spectroscopy. Solid-state NMR suggests the presence of three major components in the ceramics: (i) hexagonal boron nitride (h-BN), (ii) turbostratic boron nitride (t-BN), and (iii) BN 2 C groups. Increasing pyrolysis temperature leads to the transformation of BN 2 C groups into BN 3 and "free" carbon. A thermodynamic model is proposed to explain such transformation. Raman spectroscopy measurements reveal that the concentration of the "free" carbon cluster decreases with increasing pyrolysis temperature, and Si 4 B 1 contains more "free" carbon cluster than Si 2 B 1 . EPR studies reveal that the carbon (C)-dangling bond content also decreases with increasing pyrolysis temperature. It appears that the complete decomposition of the metastable BN 2 C groups to the BN 3 groups and the "free" carbon affects the crystallization of SiBCN, which leads to Si 4 B 1 ceramics crystallized at 1500 °C, whereas Si 2 B 1 ceramics crystallized at 1600 °C.

Polymer-derived ceramic fibers with aligned multiwalled carbon nanotubes (MWCNTs) are fabricated through the electrospinning of polyaluminasilazane solutions with well-dispersed MWCNTs followed by pyrolysis. Poly(3-hexylthiophene)-b-poly (poly (ethylene glycol) methyl ether acrylate) (P3HT-b-PPEGA), a conjugated block copolymer compatible with polyaluminasilazane, is used to functionalize MWCNT surfaces with PPEGA, providing a noninvasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions. The electrospinning of the MWCNT/polyaluminasilazane solutions generates polymer fibers with aligned MWCNTs where MWCNTs are oriented along the electrospun jet by a sink flow. The subsequent pyrolysis of the obtained composite fibers produces ceramic fibers with aligned MWCNTs. The study of the effect of polymer and CNT concentration on the fiber structures shows that the fiber size increases with the increment of polymer concentration, whereas higher CNT content in the polymer solutions leads to thinner fibers attributable to the increased conductivity. Both the SEM and TEM characterization of the polymer and ceramic fibers demonstrates the uniform orientation of CNTs along the fibers, suggesting excellent dispersion of CNTs and efficient CNT alignment via the electrospinning. The electrical conductivity of a ceramic fibers with 1.2% aligned MWCNTs is measured to be 1.58 × 10−6 S/cm, which is more than 500 times higher than that of bulk ceramic (3.43 × 10−9 S/cm). Such an approach provides a versatile method to disperse CNTs in preceramic polymer solutions and offers a new approach to integrate aligned CNTs in ceramics.