title: Conformational Evolution of Elongated Polymer Solutions Tailors the Polarization of Light-Emission from Organic Nanofibers.
abstract: Polymer fibers are currently exploited in tremendously important technologies. Their innovative properties are mainly determined by the behavior of the polymer macromolecules under the elongation induced by external mechanical or electrostatic forces, characterizing the fiber drawing process. Although enhanced physical properties were observed in polymer fibers produced under strong stretching conditions, studies of the process-induced nanoscale organization of the polymer molecules are not available, and most of fiber properties are still obtained on an empirical basis. Here we reveal the orientational properties of semiflexible polymers in electrospun nanofibers, which allow the polarization properties of active fibers to be finely controlled. Modeling and simulations of the conformational evolution of the polymer chains during electrostatic elongation of semidilute solutions demonstrate that the molecules stretch almost fully within less than 1 mm from jet start, increasing polymer axial orientation at the jet center. The nanoscale mapping of the local dichroism of individual fibers by polarized near-field optical microscopy unveils for the first time the presence of an internal spatial variation of the molecular order, namely the presence of a core with axially aligned molecules and a sheath with almost radially oriented molecules. These results allow important and specific fiber properties to be manipulated and tailored, as here demonstrated for the polarization of emitted light.
authors: National Nanotechnology Laboratory of Istituto Nanoscienze-CNR , via Arnesano, I-73100 Lecce, Italy.
authors: Andrea
authors: A
authors: Camposeo
authors: Department of Mechanical Engineering, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors: Israel
authors: I
authors: Greenfeld
authors: Dipartimento di Fisica "Enrico Fermi" and CNISM, Università di Pisa , Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy ; Istituto Nazionale di Ottica INO-CNR , Sezione di Pisa, I-56127 Pisa ( Italy ).
authors: Francesco
authors: F
authors: Tantussi
authors: National Nanotechnology Laboratory of Istituto Nanoscienze-CNR , via Arnesano, I-73100 Lecce, Italy.
authors: Maria
authors: M
authors: Moffa
authors: Dipartimento di Fisica "Enrico Fermi" and CNISM, Università di Pisa , Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy ; Istituto Nazionale di Ottica INO-CNR , Sezione di Pisa, I-56127 Pisa ( Italy ).
authors: Francesco
authors: F
authors: Fuso
authors: Dipartimento di Fisica "Enrico Fermi" and CNISM, Università di Pisa , Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy ; Istituto Nazionale di Ottica INO-CNR , Sezione di Pisa, I-56127 Pisa ( Italy ).
authors: Maria
authors: M
authors: Allegrini
authors: Department of Mechanical Engineering, Technion-Israel Institute of Technology , Haifa 32000, Israel.
authors: Eyal
authors: E
authors: Zussman
authors: National Nanotechnology Laboratory of Istituto Nanoscienze-CNR , via Arnesano, I-73100 Lecce, Italy ; Dipartimento di Matematica e Fisica "Ennio De Giorgi", Università del Salento , via Arnesano I-73100 Lecce, Italy.
authors: Dario
authors: D
authors: Pisignano