The International Istanbul Textile Congress 2013 May 30th to June 1th 2013, Istanbul, Turkey

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ONE-STEP SYNTHESIS OF POLY (VINYLIDENE FLUORIDE-CO-HEXAFLUOROPROPENE) (PVDF-CO-HFP) /SILVER NANOFIBROUS

SYSTEM Y. AYKUT1*, S. A. KHAN2, and B. POURDEYHIMI3

1Uludag University, Department of Textile Engineering, Bursa, Turkey 2North Carolina State University, Chemical and Biomolecular Engineering, NC, USA

2North Carolina State University, Textile Engineering Chemistry and Science, NC, USA aykut@uludag.edu.tr

Abstract: We demonstrate the synthesis of silver nanoparticles (Ag NPs) incorporated PVDF-co-HFP nanofibers (NFs) through reducing agent free production of silver nanoparticles in PVDF-co-HFP solution and electrospinning (ES) of the prepared solution into nanofibrous system. As-synthesized Ag NPs in the ES solution was investigated with UV-Vis spectra, as-spun Ag/ PVDF-co-HFP composite nanofibers were evaluated with a scanning electron microscopy (SEM) and a differential scanning calorimeter (DSC). The results reveal that Ag/ PVDF-co-HFP NFs were successfully prepared and melting temperature of PVDF-co-HFP increases from 128 oC to 138 oC with Ag addition. Such nanofibrous system with a high specific surface can potentially be used in a Li-ion battery to enhance device performance. Keywords: silver nanoparticles, electrospinning, PVDF-co-HFP nanofiber, ionic conductivity 1. Introduction Polymer electrolytes are promising materials for lithium-ion batteries, super capacitors, and fuel cells, because of their excellent solid state chemical stabilities [1]. Poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-co-HFP) has been considered to be one of these material as solid state battery electrolyte. Producing PVDF-co-HFP in nanoscale can enhance the device performance because more interaction can be provided from high specific surface are of the material. On the other hand one of the challenges to enhance device performance is to increase ionic conductivity of PVDF-co-HFP. In the literature several salts have been doped in PVDF-co-HFP to overcome this problem [2]. In this study we dissolve AgNO3 in PVDF-co-HFP solution ans produced Ag NPs embedded PVDF-co-HFP NFs from the subsequent solution via electrospinning technique. 2. Materials and Methods

PVDF-co-HFP/DMF/acetone solution is prepared with magnetically stirring at an ambient condition until getting a homogeneous polymer solution. Then, a proper rate of AgNO3 is added into the solution and continued to stirring. Ag NPs started to reduce on the polymer chains and grow as a result of stirring. Then, the prepared solution is directly electrospun into nanofibers. The detail of the ES process is explained in Reference 3. 3. Results and Discussions UV-Vis absorption spectrum is collected to confirm the formation of Ag NPs. As seen from the spectra (Fig. 1), absorption intensity is significantly increased with increasing solution stirring time because of formation and growth of Ag Nanoparticles. SEM investigation of as-spun PVDF-co-HFP and Ag-doped PVDF-co-HFP nanofibers are demonstrated in Fig. 2. As seen from the Fig. 2A and 2B, as-spun PVDF-co-HFP are in the form of 3D interwoven structure, and the fibers are randomly distributed and the surface of the fibers are extremely smooth (Fig. 2A and 2B). When Ag NPs are doped in the fibers, surfaces of the fibers become rougher and fiber diameters decrease significantly (Fig. 2C and 2D). Thermal analyses of the fibers were performed with a DSC and shown in Fig. 3. Appearance of an exothermic peak at around 128 oC is attributed to melting point of the semi crystalline pure PVDF-co-HFP nanofibers (Fig 3a). This peak shifts to a higher temperature with addition of Ag NPs into NFs (Fig 3a, 3b) because the existence of NPs intends to decrease the segmental mobility of the polymer chains in the NFs as a result of steric hindrance effect [1].

The International Istanbul Textile Congress 2013 May 30th to June 1th 2013, Istanbul, Turkey

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Figure 1. UV-Vis absorption spectrum Ag NPs in PVDF-co-HFP/ AgNO3/DMF/acetone solutions with differing stirring time: a)0 , b)10, c)30 minutes,and with addition of CaOH d) 10 min, e)30 min.

Figure 2. Low and high magnification SEM images of A, B) PVDF-co-HFP, C,D) Ag doped PVDF-co-HFP nanofibers

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The International Istanbul Textile Congress 2013 May 30th to June 1th 2013, Istanbul, Turkey

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4. CONCLUSION

Ag/PVDF-co-HFP composite nanofibers were prepared successfully via electrospinning technique. The addition of Ag NPs into PVDF-co-HFP NFs increases the melting point of the polymer as a result of reducing segmental mobility of polymer chains. The prepared system can be considered a potential candidate to use as polymer electrolyte in li-ion batteries. References [1] Kalyana Sundaram, N. T.; Subramania, A.: Electrochim. Acta (2007), 52, 4987-4993. [2] Ulaganathan, M.; Rajendran,S.: J. Appl. Poly. Sci. (2010), 118, 646-651. [3] Saquing, C. D.;Manasco, J. L.; Khan, S.A.: Small (2009) 5, 944-951