On the Importance of Noncrystalline Phases in Semicrystalline Electrospun Nanofibers

Soleimani, Foad; Mazaheri, Mehdi; Pellerin, Christian; Bagheri, Reza

doi:10.1021/acsapm.1c01088

Cited by 8 publications

(14 citation statements)

References 50 publications

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“…The prominent T g and T cc observed in the as-spun NF were no longer evident in the heat-set PET t-shirt NF. This observation is consistent with previous reports 25,26 and provides evidence of how heat-setting could have affected the polymer chains of the polyester textile fibers.…”

Section: ■ Results and Discussionsupporting

confidence: 93%

“…Similar unclear glass transition and cold crystallization behavior have commonly been observed for annealed PET samples. , The growth of the crystalline region restricts the mobility of the chains in the amorphous phase, leading to a broadening of the glass transition range . Cold crystallization arises from the presence of highly ordered chains that can easily reorganize into crystals . Therefore, it is likely that those locally aligned chains transformed into crystals during the heat-setting process of polyester textile manufacturing.…”

Section: Resultssupporting

confidence: 53%

“…25 Cold crystallization arises from the presence of highly ordered chains that can easily reorganize into crystals. 26 Therefore, it is likely that those locally aligned chains transformed into crystals during the heat-setting process of polyester textile manufacturing. To further support the above discussion, Figure S3 shows the DSC thermogram of the PET t-shirt NF subjected to a 1-h heat setting at 150 °C, along with that of the as-spun PET tshirt NF.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Structural Investigation on Electrospun Nanofibers from Postconsumer Polyester Textiles and PET Bottles

Ko,

Hinestroza,

Uyar

2023

ACS Appl. Polym. Mater.

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This study investigates the structural and physical properties of electrospun nanofibers (NF) produced from postconsumer poly(ethylene terephthalate) (PET) textile sources, including a no-dye polyester fabric, a 50/50 (by weight) mixture of red-and blue-dye polyester fabric, a polyester t-shirt, and from a postconsumer PET bottle. The postconsumer PET sources and their corresponding electrospun NF exhibited similar chemical structures and melting points. However, the electrospun PET NF showed distinct cold crystallization and sharper melt-crystallization behavior during rapid cooling as well as improved resolution of their Fourier transform infrared spectra. We hypothesize that this behavior can be attributed to the presence of locally ordered mesophases in the electrospun PET NF caused by rapid stretching of the electrically charged jet during electrospinning. The electrospun NF were found to be more amorphous, to have a lower degree of crystallinity, and to exhibit weakened signals of the trans conformers of the glycol units, when compared to their original postconsumer PET sources. Polyester-textile NF showed smaller average fiber diameters, higher degrees of crystallinity, higher melt-crystallization temperatures, and more rigidity than those of NF produced from PET bottles. The electrospun NF acquired from postconsumer PET textiles and bottles may hold promise as a versatile material for filtration, protective clothing, and environmental remediation.

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Section: ■ Results and Discussionsupporting

confidence: 93%

Section: Resultssupporting

confidence: 53%

Section: ■ Results and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Structural Investigation on Electrospun Nanofibers from Postconsumer Polyester Textiles and PET Bottles

Ko,

Hinestroza,

Uyar

2023

ACS Appl. Polym. Mater.

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“…ES fabrics were immediately removed from the substrate and dried in a vacuum oven at 30 °C for 48 h. After drying, no significant amount of solvents was detectable according to our previous study. 8 The ES fabrics were named L.…”

Section: Fabrication Of Hydrophobic/hydrophilic Compositesmentioning

confidence: 99%

Engineered Robust Hydrophobic/Hydrophilic Nanofibrous Scaffolds with Drug-Eluting, Antioxidant, and Antimicrobial Capacity

Soleimani,

Pellerin,

Omidfar

et al. 2024

ACS Appl. Bio Mater.

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Multifunctional nanofibrous architectures have attracted extensive attention for biomedical applications due to their adjustable and versatile properties. Electrospun fabrics stand out as key building blocks for these structures, yet improving their mechanobiological and physicochemical performance is a challenge. Here, we introduce biodegradable engineered hydrophobic/hydrophilic scaffolds consisting of electrospun polylactide nanofibers coated with drug-eluting synthetic (poly(vinyl alcohol)) and natural (starch) polymers. The microstructure of these composite scaffolds was tailored for an increased hydrophilicity, optimized permeability, water retention capacity of up to 5.1 g/g, and enhanced mechanical properties under both dry and wet conditions. Regarding the latter, normalized tensile strengths of up to 32.4 MPa were achieved thanks to the improved fiber interactions and fiber-coating stress transfer. Curcumin was employed as a model drug, and its sustained release in a pure aqueous medium was investigated for 35 days. An in-depth study of the release kinetics revealed the outstanding water solubility and bioavailability of curcumin, owing to its complexation with the hydrophilic polymers and further delineated the role of the hydrophobic nanofibrous network in regulating its release rate. The modified curcumin endowed the composites with antioxidant activities up to 5.7 times higher than that of free curcumin as well as promising anti-inflammatory and bacteriostatic activities. The cytocompatibility and cell proliferation capability on human dermal fibroblasts also evidenced the safe use of the constructs. Finally, the fabrics present pH-responsive color-changing behavior easily distinguishable within the pH range of 5–9. Thus, these designs offer a facile and cost-effective roadmap for the fabrication of smart multifunctional biomaterials, especially for chronic wound healing.

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“…After solvent removal, we speculate that these string structures and/or assemblies of the strings evolved in the jet may be transformed to become a stack of the fibrils and/or stacks of the assemblies of the fibrils in the solid fibers. In other words, the strings in the electrospinning jet evolve into the fibrils in the as-spun fibers in the extremely short electrospinning time of about 0.05 s. Formation of fibrillar structure in the electrospun fibers has been proposed, − and direct observations of fibrils are occasionally reported. , Moreover, the enhanced elastic modulus as fiber diameter is reduced is attributed to the fibrillar structure in the nanofibers . The development of crystalline phase, such as the crystal structure and crystal orientation, during such a rapid process deserves systematic investigations.…”

Section: Introductionmentioning

confidence: 99%

Poly(vinyl alcohol) Fibrils with Highly Oriented Amorphous Chains Developed in Electrospun Nanofibers

Wang,

Tsai,

Hashimoto

2024

Macromolecules

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Aligned poly(vinyl alcohol) (PVA) fibers with diameters of about 180 ± 22 nm were obtained by using a wire−drum collector during electrospinning of aqueous solutions of PVA with 99% hydrolysis. The fiber orientation factor, defined by the Herman's orientation function, was about 0.95 with respect to the collecting direction. Subjected to a stepwise heating protocol, the crystal orientation and crystallinity in the aligned fibers at different annealing temperatures (T a ) were determined by using Fourier transform infrared spectroscopy (FTIR) and synchrotron 2D wide-angle X-ray diffraction (WAXD). Upon heating, FTIR results disclosed the desorption of residual water molecules at T a < 100 °C and an increase in crystal orientation at elevated temperatures as-revealed by the decreasing dichroism of the crystal-related band at 1143 cm −1 until fiber melting, followed by thermal degradation at T a ≳ 190 °C. The enhanced crystal orientation along the fiber axis at high T a (≳100 °C) was also validated by the detailed analyses of the 2D WAXD patterns to extract the Herman's orientation factor of the reciprocal lattice vectors of the (101/101̅ ) crystal planes from which the chain orientation factor in the crystalline phase was derived to dramatically increase from 0.57 at 35 °C to reach the highest value of 0.88 at 200 °C. Meanwhile, the fiber crystallinity was also increased upon heating from 31% at 35 °C to 35% at 100 °C and further up to 37% at 180 °C. The peculiar two-step enhancement in the crystal orientation and fiber crystallinity at elevated temperatures is attributed to the presence of the fibrils comprising the fiber, which are composed of highly oriented amorphous chains as well as the loosely packed amorphous chains existing in between the oriented crystalline domains. The presence of fibrils and fiber bundles (superstructures of the fibrils) was validated by atomic force microscopy as well as scanning and transmission electron microscopy. The highly oriented amorphous chains were disclosed by the anomalous meridional X-ray diffraction with a unique spacing of 2.44 Å, which is associated with the spacing along the chain axis in the closely packed and aligned chains with zigzag conformation. These extended amorphous chains may form strong intrachain and interchain hydrogen bonds, which firmly hold the fiber integrity for restricting orientation relaxation of chain molecules upon heating, therefore, to readily proceed the chain reorganization and develop oriented crystals directly at high T a . The unique features of fibrils existing in the as-spun PVA fibers are relevant to the flow-induced phase separation of the electrospinning jet to produce phase-separated structure of strings with various widths. A discussion on the structures evolved from the liquid strings to the solid fibrils and subsequent heating effect is provided.

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On the Importance of Noncrystalline Phases in Semicrystalline Electrospun Nanofibers

Cited by 8 publications

References 50 publications

Structural Investigation on Electrospun Nanofibers from Postconsumer Polyester Textiles and PET Bottles

Structural Investigation on Electrospun Nanofibers from Postconsumer Polyester Textiles and PET Bottles

Engineered Robust Hydrophobic/Hydrophilic Nanofibrous Scaffolds with Drug-Eluting, Antioxidant, and Antimicrobial Capacity

Poly(vinyl alcohol) Fibrils with Highly Oriented Amorphous Chains Developed in Electrospun Nanofibers

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