Quantitative characterization of dielectric properties of polymer fibers and polymer composites using electrostatic force microscopy
| Autor: | Anuja S Jayasekara, Cristian Staii, Peggy Cebe, Ilya Yurchenko |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Materials science
Polymer nanocomposite Electrostatic force microscope Bioengineering 02 engineering and technology Dielectric Carbon nanotube 010402 general chemistry 01 natural sciences law.invention Scanning probe microscopy law General Materials Science Fiber Electrical and Electronic Engineering Composite material chemistry.chemical_classification Mechanical Engineering General Chemistry Polymer 021001 nanoscience & nanotechnology 0104 chemical sciences chemistry Mechanics of Materials Nanofiber 0210 nano-technology |
| Zdroj: | Nanotechnology. 31(50) |
| ISSN: | 1361-6528 |
| Popis: | We use a new method based on electrostatic force microscopy (EFM) to perform quantitative measurements of the dielectric constants of individual electrospun nanofibers of poly(L-lactic acid) (PLLA), as well as composite fibers of PLLA with embedded multiwall carbon nanotubes (MWCNT-PLLA). The EFM data record the oscillation phase of an atomic force microscope (AFM) cantilever as a function of the AFM tip position. In our experiments the relative dielectric constants ϵ of the sample are measured from the EFM phase shifts vs. the tip-surface separation, according to a simple analytical model describing the tip-surface interactions. We perform a comprehensive study of how the dielectric constant depends on the fiber diameter for both electrospun PLLA and MWCNT/PLLA fiber composites. Our measurements show that EFM can distinguish between dielectric properties of PLLA fibers and fiber composites with different diameters. Dielectric constants of both PLLA and MWCNT-PLLA composite fibers decrease with increasing fiber diameter. In the limit of large fiber diameters (D > 100 nm), we measure dielectric constants in the range: ϵ = 3.4–3.8, similar to the values obtained for unoriented PLLA films: ϵfilm = 2.4–3.8. Moreover, the dielectric constants of the small diameter MWCNT-PLLA composites are significantly larger than the corresponding values obtained for PLLA fibers. For MWCNT-PLLA nanofiber composites of small diameters (D < 50 nm), ϵ approaches the values measured for neat MWCNT: ϵCN = 12 ± 2. These results are consistent with a simple fiber structural model that shows higher polarizability of thinner fibers, and composites that contain MWCNTs. The experimental method has a high-resolution for measuring the dielectric constant of soft materials, and is simple to implement on standard atomic force microscopes. This non-invasive technique can be applied to measure the electrical properties of polymers, interphases, and polymer nanocomposites. |
| Databáze: | OpenAIRE |
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