TY - JOUR
T1 - Quantifying Polymer Chain Orientation in Strong and Tough Nanofibers with Low Crystallinity
T2 - Toward Next Generation Nanostructured Superfibers
AU - Papkov, Dimitry
AU - Delpouve, Nicolas
AU - Delbreilh, Laurent
AU - Araujo, Steven
AU - Stockdale, Taylor
AU - Mamedov, Sergey
AU - Maleckis, Kaspars
AU - Zou, Yan
AU - Andalib, Mohammad Nahid
AU - Dargent, Eric
AU - Dravid, Vinayak P.
AU - Holt, Martin V.
AU - Pellerin, Christian
AU - Dzenis, Yuris A.
N1 - Funding Information:
This work was supported in part by the grants from ONR (N000141410663), NSF (DMR-1310534, CMMI-1463636), and NIH (1R01HL125736-01). C.P. acknowledges the support from the Natural Sciences and Engineering Council of Canada. M.H. acknowledges the support of the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-06CH11357. The authors thank Bruce Chase of University of Delaware, Dmitri Basov of Columbia University, Alan D. English of Macromolecules journal, and Martha Morton of University of NebraskaLincoln for reading sections of this work and valuable comments; Tobias Gokus and Nicolai Hartmann from neaspec GmbH for their help with nano-FTIR measurements; and Joel Brehm of UNL for his help with creating graphical schematics for this paper.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/5/28
Y1 - 2019/5/28
N2 - Advanced fibers revolutionized structural materials in the second half of the 20th century. However, all high-strength fibers developed to date are brittle. Recently, pioneering simultaneous ultrahigh strength and toughness were discovered in fine (<250 nm) individual electrospun polymer nanofibers (NFs). This highly desirable combination of properties was attributed to high macromolecular chain alignment coupled with low crystallinity. Quantitative analysis of the degree of preferred chain orientation will be crucial for control of NF mechanical properties. However, quantification of supramolecular nanoarchitecture in NFs with low crystallinity in the ultrafine diameter range is highly challenging. Here, we discuss the applicability of traditional as well as emerging methods for quantification of polymer chain orientation in nanoscale one-dimensional samples. Advantages and limitations of different techniques are critically evaluated on experimental examples. It is shown that straightforward application of some of the techniques to sub-wavelength-diameter NFs can lead to severe quantitative and even qualitative artifacts. Sources of such size-related artifacts, stemming from instrumental, materials, and geometric phenomena at the nanoscale, are analyzed on the example of polarized Raman method but are relevant to other spectroscopic techniques. A proposed modified, artifact-free method is demonstrated. Outstanding issues and their proposed solutions are discussed. The results provide guidance for accurate nanofiber characterization to improve fundamental understanding and accelerate development of nanofibers and related nanostructured materials produced by electrospinning or other methods. We expect that the discussion in this review will also be useful to studies of many biological systems that exhibit nanofilamentary architectures and combinations of high strength and toughness.
AB - Advanced fibers revolutionized structural materials in the second half of the 20th century. However, all high-strength fibers developed to date are brittle. Recently, pioneering simultaneous ultrahigh strength and toughness were discovered in fine (<250 nm) individual electrospun polymer nanofibers (NFs). This highly desirable combination of properties was attributed to high macromolecular chain alignment coupled with low crystallinity. Quantitative analysis of the degree of preferred chain orientation will be crucial for control of NF mechanical properties. However, quantification of supramolecular nanoarchitecture in NFs with low crystallinity in the ultrafine diameter range is highly challenging. Here, we discuss the applicability of traditional as well as emerging methods for quantification of polymer chain orientation in nanoscale one-dimensional samples. Advantages and limitations of different techniques are critically evaluated on experimental examples. It is shown that straightforward application of some of the techniques to sub-wavelength-diameter NFs can lead to severe quantitative and even qualitative artifacts. Sources of such size-related artifacts, stemming from instrumental, materials, and geometric phenomena at the nanoscale, are analyzed on the example of polarized Raman method but are relevant to other spectroscopic techniques. A proposed modified, artifact-free method is demonstrated. Outstanding issues and their proposed solutions are discussed. The results provide guidance for accurate nanofiber characterization to improve fundamental understanding and accelerate development of nanofibers and related nanostructured materials produced by electrospinning or other methods. We expect that the discussion in this review will also be useful to studies of many biological systems that exhibit nanofilamentary architectures and combinations of high strength and toughness.
KW - chain orientation quantification
KW - characterization of subwavelength-diameter nanofibers
KW - continuous nanofibers
KW - electrospinning
KW - low crystallinity
KW - macromolecular orientation
KW - nanoscale-related artifacts
KW - simultaneously strong and tough nanofibers
KW - size effects in nanofibers
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U2 - 10.1021/acsnano.8b08725
DO - 10.1021/acsnano.8b08725
M3 - Review article
C2 - 31038925
AN - SCOPUS:85066853266
VL - 13
SP - 4893
EP - 4927
JO - ACS Nano
JF - ACS Nano
SN - 1936-0851
IS - 5
ER -