Spatially Confined Fabrication of Polar Poly(Vinylidene Fluoride) Nanotubes

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 18; no. 51; pp. e2205790 - n/a
• Main Authors: Hou, Chunyue, Zhang, Wenxian, Dai, Xiying, Qiu, Jieshan, Russell, Thomas P., Sun, Xiaoli, Yan, Shouke
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.12.2022
• Subjects: ageing; Aging; alkali treatments; Aluminum oxide; anodized aluminum oxide membranes; Crystallinity; Crystallization; Crystals; Ferroelectricity; Fluorides; Membranes; Nanomaterials; Nanotechnology; Nanotubes; Piezoelectricity; polar PVDF nanotubes; Polyvinylidene fluorides; Potassium hydroxides; Room temperature; Vinylidene fluoride; alkali treatments; polar PVDF nanotubes; ageing; anodized aluminum oxide membranes
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202205790

Polar poly(vinylidene fluoride) (PVDF) nanotubes have attracted significant attention due to their excellent piezoelectric and ferroelectric properties, yet a tunable fabrication of homogeneous polar PVDF nanotubes remains a challenge. Here, a simple method is reported to fabricate polar PVDF nanotubes using anodize aluminum oxide (AAO) membranes as templates that are removed by etching in a potassium hydroxide (KOH) solution and then ageing at room temperature. PVDF nanotubes originally crystallized in the AAO membrane are pure α‐crystals with very low crystallinity, yet after being released from the templates, the crystallinity of the nanotubes markedly increases with ageing at room temperature, leading to the formation of β‐PVDF crystals in a very short time, with the formation of γ crystals after longer ageing times. A large amount of γ crystals formed when the released PVDF nanotubes are heated to ≈130 °C. The formation of polar PVDF nanotubes released from the AAO templates treated with higher concentrations of alkaline solution results from the reaction of the surface of the PVDF nanotubes with the alkaline solution and structure reorganization under confined conditions. This large‐scale preparation of β‐ and γ‐PVDF opens a new pathway to produce polar PVDF nanomaterials. Polar poly(vinylidene fluoride) nanotubes are fabricated using anodize aluminum oxide templates etched in a high concentration of KOH solution followed by a simple room temperature ageing. A large amount of polar phase can also form by heating. The unusual formation of polar nanotubes can be ascribed to the synergistic effect of confinement and alkaline solution.