期刊
APPLIED SPECTROSCOPY
卷 -, 期 -, 页码 -出版社
SAGE PUBLICATIONS INC
DOI: 10.1177/00037028231202791
关键词
Anisotropic; applications; materials; polymers; quantitative analysis; Raman spectroscopy
This study investigates the use of solvent volatility to improve the molecular orientation and crystallinity of polymer fibers. Highly volatile solvents rapidly increase the glass transition temperature of the polymer jet during electrospinning, resulting in higher and sustained orientation.
Electrospun fibers of amorphous or low-crystallinity polymers typically exhibit a low molecular orientation that can hamper their properties and application. A key stage of the electrospinning process that could be harnessed to mitigate the loss of orientation is jet rigidification, which relates closely to the solvent evaporation rate. Here, we establish quantitative Raman methods to assess the molecular orientation and crystallinity of weakly crystalline poly(2,6-dimethyl-1,4-phenylene oxide) fibers with varying diameters. Our findings demonstrate that solvent volatility can be leveraged to modulate the orientation and crystallinity through its impact on the effective glass transition temperature (T-g,T-eff) of the polymer jet during the electrospinning process. Specifically, a highly volatile solvent yields a higher and more sustained orientation (median P2 > of 0.53 for diameters < 1.0 mu m) because its fast evaporation rapidly increases T-g,eff above room temperature. This vitrification early along the jet path promotes the formation of an oriented amorphous phase and a moderate fraction of strain-induced crystals. Our data reveals that a high T-g is a crucial parameter for reaching high orientation in amorphous or low-crystallinity polymer systems.
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