WO₃Nanowires Enhance Molecular Alignment and Optical Anisotropy in Electrospun Nanocomposite Fibers: Implications for Hybrid Light-Emitting Systems

Abstract

The molecular orientation in polymer fibers is investigated for the purpose of enhancing their optical properties through nanoscale control by nanowires mixed in electrospun solutions. A prototypical system, consisting of a conjugated polymer blended with polyvinylpyrrolidone, mixed with WO 3 nanowires, is analyzed. A critical strain rate of the electrospinning jet is determined by theoretical modeling at which point the polymer network undergoes a stretch transition in the fiber direction, resulting in a high molecular orientation that is partially retained after solidification. Nearing a nanowire boundary, local adsorption of the polymer and hydrodynamic drag further enhance the molecular orientation. These theoretical predictions are supported by polarized scanning near-field optical microscopy experiments, where the dichroic ratio of the light transmitted by the fiber provides evidence of increased orientation nearby nanowires. The addition of nanowires to enhance molecular alignment in polymer fibers might consequently enhance properties such as photoluminescence quantum yield, polarized emission, and tailored energy migration, exploitable in light-emitting photonic and optoelectronic devices and for sensing applications.

Stiffness modeling of thermoset polymer fibers

“…, a linear dependence on the extension; at high extension, as chain conformations become less probable, the force rises sharply by a nonlinear function such as 1Àϵ 0 1Àϵ . 11,16,20 Thus:…”

“…The stretching equation bears similarity in form to the stretching of entangled linear polymer chains. 11,20 However, the thermoset polymer size and its relaxation time are completely different: ξ 0 $ N 0:4 (compared to $ N 0:6 ), L $ N 0:67 (compared to $ N), and τ $ N 1:8 or 1:2 (compared to $ N 3 ), being much more compact and with faster relaxation. The difference stems from the dissimilar physical state of the two polymer types.…”

“…Þthat a monomer will be aligned with each of the six possible directions. 11,20 x is the flow longitudinal axis, whereas y and z are the lateral axes. The (+) and (À) signs indicate the positive and negative directions of each axis, respectively.…”

“…The elongation of thermoplastic polymers under extensional flow has been broadly investigated, using the concepts of linear flexible chains, confining tube, chain reptation, and chain stretching and retraction. [11][12][13][14][15][16][17][18][19][20] The general polymer behavior is similar in thermosets, consisting of stretching of chains under the stresses induced by an extensional flow, followed by partial retraction due to the elastic forces in chains, which relieves some of the stress and achieves a new state of equilibrium. [21][22][23][24][25] However, the two polymer types are quite different, and therefore their modeling differs.…”

Ibuprofen-Loaded ZnO Nanoparticle/Polyacrylonitrile Nanofibers for Dual-Stimulus Sustained Release of Drugs

“…Numerous medicated nanoparticles have found their potential applications in drug delivery, while electrospinning has wide application prospects in the field of transdermal drug delivery. − Electrospinning is able to treat many kinds of fluids, including solutions, , emulsions, , and nano-suspensions, , and in several manners such as blending, , coaxial, and multiple fluid . Drug-loaded electrospun nanofiber membranes have large specific surface areas, high porosity, and high fluid absorption, which induce a humid environment on the skin cuticle, allowing the fiber membrane to closely fit to the skin, thereby helping drugs enter systemic circulation in the way of dissimilar diffusion along a concentration gradient. − Polyacrylonitrile (PAN) is widely used for electrospinning because of its good electrospinnability and stability .…”