Effect of stimuli-responsive polydiacetylene on the crystallization and mechanical properties of PVDF nanofibers
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Effect of stimuli‑responsive polydiacetylene on the crystallization and mechanical properties of PVDF nanofibers Najmeh Moazeni1 · Mehdi Sadrjahani1 · Ali Akbar Merati1,2 · Masoud Latifi1 · Shohre Rouhani3,4 Received: 21 April 2019 / Revised: 23 October 2019 / Accepted: 8 November 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract To improve the β-phase content of polyvinylidene fluoride (PVDF), diacetylene (DA) monomers were embedded in PVDF nanofibers. The PVDF/DA nanofiber membranes were fabricated using the electrospinning technique and polymerized to form polydiacetylene (PDA) after UV irradiation. In this study, the effect of PDA on the crystalline structure of PVDF nanofibers was examined and compared with cast films. The nanofiber morphology was assessed by SEM, while Fourier transform infrared spectroscopy and wide-angle X-ray diffraction were performed to characterize the crystallinity behavior. The mechanical properties and crystal polymorphism of the electrospun PVDF/DA nanofibers were also studied before irradiation, after irradiation and after colorimetric transition induced by the heat treatment. The results showed that the addition of PDA can effectively improve β-phase crystalline PVDF in both the as-cast film and the electrospun nanofibers which is greater in the latter. The electrospun PVDF/DA nanofibers after UV irradiation exhibit greater intensity of β-phase in comparison with those before irradiation. Furthermore, the fraction of β-phase decreased when the blue phase of the PVDF–PDA nanofibers undergoes a heat-induced thermochromic transition to a red phase. The tensile strength and elongation at break as well as the tensile modulus were notably improved after heat treatment of the electrospun PVDF–PDA nanofibers. Keywords Polyvinylidene fluoride · Polydiacetylene · Electrospinning · UV irradiation
* Najmeh Moazeni [email protected] Extended author information available on the last page of the article
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Polymer Bulletin
Introduction Polyvinylidene fluoride (PVDF) has been widely investigated due to its attractive properties such as piezo-, pyro- and ferroelectricity, flexibility, lightweight, excellent chemical stability, mechanical strength and good processability with applications such as sensors and actuators in microelectromechanical systems (MEMS), energy harvesters and nonvolatile memories in microelectronics [1, 2]. PVDF exhibits at least five crystalline phases, with different conformations, all-trans (TTTT) in the β-phase, an alternation of trans and gauche (TGTG′) in α- and δ-phases and TTTGTTTG′ in γ- and ε-phases [3, 4]. Among these crystal phases, the α-phase is the most common phase where the net dipole moment is zero due to its antiparallel arrangement of fluoride atoms along the carbon backbone. The β-phase comprises fluorine atoms and hydrogen atoms on opposite sides of the carbon backbone which are responsible for the piezo- and pyroelectrical properties [5, 6]. Therefore, the main interest is focused on the polar β-
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