Study on the Poly(ether ketone)(PK) nanofibrous membrane via electrospinning Graduate School of Engineering, Shinshu University Master’s degree Osamu Ohsawa

Reserch Topics Characterization of PK nanofibrous membrane via electrospinning Property comparison between electrospun PK nanofiber and Gel-spun PK microfiber

Poly(ether ketone) Properties: fast crystallization CYBERLONTM Properties: fast crystallization high tensile strength high chemical and wear resistance very low permaeability good impact behavior over a broad temperature range

Electrospinning & Gel-spinning

Features & Applications of Nanofiber Web Large surface area Small pore size High porosity Ref. Z. Huang et al. Comps. Sci. Technol. 2003, 63, 2223. Medical Prosthesis Filtration Composite Tissue Template Liquid crystal device Electromagnetic shielding 3D structure of E-spun fibers

Electrospinning parameters Solution properties → Viscosity (centipoise) → Conductivity (μS/cm) → Surface tension (dyne/cm) Controlled variables → Hydrostatic pressure in the capillary → Applied voltage → Tip-to-collector distance Ambient parameters → Temperature, Humidity → Air velocity in the electrospinning chamber

Experimental Materials Conditions Polymer: Poly(ether ketone)(IV:2.3) Applied voltage: 10kV Solvents: Trifluoroacetic acid (TFA) dichloromethane (MC) Tip-to Collector distance: 15cm Solution concentration:6-14wt% Temperature: RT Mixture solvent ratio (TFA/MC,w/w) : 30/70, 40/60, 50/50, 75/25, 100/0 Humidity: 40%

Solution properties & Morphologies Effect of concentration 2μm 6wt% 8wt% 10wt% 12wt% Concentration Viscosity Surface tension [wt%] [cP] [mN/m] 6 90 20.9 8 234 22.2 10 541.4 23.2 12 943.3 23.9 14 1725 24.7

Solution properties & Morphologies 30% 40% 75% 100% Effect of mixture solvent TFA content(%) Optimum condition Concentration:12wt% TFA/MC=40/60, 50/50

Time dependence of PK solution 0h 5h 10h 24h 0h 5h 10h 24h 2μm 2μm 2μm 2μm

Crystal structure α form β form b b a a Intermolecular dipole-dipole bonds Intermolecular hydrogen bonds α form β form Fabrication method (Spinning, Drawing) Transformation condition α→β Temperature Crystallization kinetics etc… a (Å) b (Å) c (Å) ρc(g/cm3) α 6.87 5.12 7.6 1.39 β 8.24 4.74 7.58 1.26

WAXD α α α α α α α Intensity (a.u.) β β 2theta (degree) 10 20 30 40 50 (110) (301) (210) (200) (111) (101) (103) (212) α Intensity (a.u.) α α α α α α β Solvent cast PK film β (201) (210) Electrospun PK fiber 10 20 30 40 50 2theta (degree)

DSC α→β Heat Flow (J/g) Temperature (oC) 50 100 150 200 250 300 Solvent cast PK film 50 100 150 200 250 300 Electrospun PK fiber Heat Flow (J/g) Crystallinity 1J/g E-spun fiber: 48% Solvent cast film: 56% Temperature (oC)

Raman Wavenumbers (cm-1) 1000 1200 1400 1600 1800 -CH2- symmetric stretching(νs) -CH2- asymmetric stretching(νa) C=O　stretching (ν) -CH2- bending(δ) 2700 2800 2900 3000 3100 -CH2- twisting(γt) C-C stretching(ν) Solvent cast PK film Electrospun PK fiber 1000 1200 1400 1600 1800 Wavenumbers (cm-1)

Raman Wavenumber(cm ) α-form β-form 1440cm-1 1412cm-1 1418cm-1 Solvent cast PK film Electrospun PK fiber 1350 1400 1450 Wavenumber(cm -1 )

FT-IR Transmittance (%) Wavenumbers (cm-1) 4000 3500 3000 2500 2000 Solvent cast PK film Electrospun PK fiber -CH2- symmetric stretching (νs) -CH2- twisting Transmittance (%) Skeletal vibration -CH2- bending(δ) inter unit CC stretching(ν) -CH2-Wagging 5% ν (C=O) 4000 3500 3000 2500 2000 1500 1000 500 Wavenumbers (cm-1)

Conclusion PK nanofibers have been successfully electrospun from the solution. The optimized concentration and mixture solvent ratio of the solution for electrospinning were 12wt% and TFA/MC (40/60,w/w), respectively. Different crystalline forms of electrospun PK fiber and solvent cast PK film were confirmed by XRD, FT-IR, and Raman spectroscopy. Solvent cast PK film showed completely α-form, while electrospun PK fiber showed β-form, suggesting the different crystallization kinetics and stress induced crystalline transformation during electrospinning and solvent casting process.

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WAXD Intensity 1000 2theta (o) Stretched Gel-spun PK fiber 10 20 30 40 50 Intensity 2theta (o) 1000 Gel-spun PK fiber Electrospun PK fiber Stretched Gel-spun PK fiber

FT-IR Transmittance (%) Wavenumbers (cm-1) 5 4000 3500 3000 2500 2000 1500 1000 Wavenumbers (cm-1)