In Situ Formation of Nanohybrid Shish-Kebabs during Electrospinning for the Creation of Hierarchical Shish-Kebab Structures

Abstract

We successfully tested the hypothesis that the nanohybrid shish-kebab (NHSK) structure, i.e., polymer kebabs on a CNT shish, can be created in situ during electrospinning. In addition, the resulting nanofibers containing the NHSKs were used to create a hierarchical structure by introducing a second level of shish-kebabs: the nanofiber shish-kebab (NFSK), i.e., polymer kebabs on the nanofiber shish. A multiwalled CNT/poly­(ε-caprolactone) (MWCNT)/(PCL) solution was electrospun to form nanofibers of Ø ≈ 100 nm. The MWCNTs aligned in fiber direction within the MWCNT/PCL nanofibers. The first time creation of the NHSK during electrospinning was confirmed by bright field diffraction contrast in the transmission electron microscope. The NFSK was created by incubating the NHSK containing nanofibers in a supersaturated PCL solution. A simple model explaining the in situ NHSK formation is presented. The hierarchical structure based on the shish-kebab morphology is proposed as a high-performing building block in future advanced materials.

The formation of a nanohybrid shish-kebab (NHSK) structure in melt-processed composites of poly(ethylene terephthalate) (PET) and multi-walled carbon nanotubes (MWCNTs)

“…A TCL morphology, predominantly occurs where MWCNT mass fractions are high (up to 80% wt aggregating into fibres or arrays) and the polymer is crystallized from solution giving a compact layer on the surface of the MWCNT fibres and improved MWCNT dispersion [23,24]. Further to this, a hierarchal NHSK type of morphology was recently reported for electrospun poly(Ɛ-caprolactone)(PCL) -MWCNT composites, where a secondary 'nanofiber shish-kebab' (NFSK) crystalline morphology evolved after the incubation of the NHSK nanofibers in solution [25]. Similarly, a layered structure has been suggested in Nylon 11-MWCNT composites where a uniform crystalline layer of polymer forms prior to a NHSK structure [26].…”

Confirmation of a nanohybrid shish‐kebab (NHSK) structure in composites of PET and MWCNTs

“…However, a “nanohybrid shish‐kebab” (NHSK) morphology is also possible, where individual CNTs act as heterogeneous nucleation sites (or shish) where polymer chains wrap around them and crystallites (kebabs) grow epitaxially outwards during crystallization . Recently, a hierarchal NHSK has been reported for electrospun poly(ε‐caprolactone) MWCNT composites; here a secondary level of structure termed “nanofiber shish‐kebab” (NFSK) evolved after incubation of the NHSK nanofibers in solution …”

Periodic Functionalization of Graphene‐Layered Alumina Nanofibers with Aromatic Thermosetting Copolyester via Epitaxial Step‐Growth Polymerization

“…Similarly, Resasco and co‐workers demonstrated that single‐walled CNT reinforced polypropylene formed an in situ crystallinity . Jandt and co‐workers investigated poly(ε‐caprolactone) with multi‐walled CNTs and they observed the development of hierarchical shish–kebab structures . Kumar and co‐workers studied the CNT‐based fibers in polyethylene and showed the formation of transcrystalline lamella regions upon successive melting and recrystallization processes .…”