Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). To control the diameter, morphology, and structure of PVDF nanofibers, some parameters were investigated, such as polymer concentration, nozzle‐to‐ground collector distance, feeding rate of the polymer solution, and applied voltage. The fabricated fiber was 80–700 nm in diameter. The increase in the polymer concentration caused an increase in the polymer viscosity and fiber diameter. At low polymer concentration (5 wt %), polymer nanoparticles were formed. An increase in applied voltage will increase the fiber diameter. Variation in the nozzle‐to‐ground collector distance did not result in significant changes in the fiber diameter. Increase in the feeding rate of the polymer solution decreased the fiber diameter. Differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) measurements showed that the melting point and total crystallinity were decreased. Fourier transform infrared spectroscopy (FTIR) measurement revealed that ESD process induced the formation of the oriented β‐phase PVDF structures. It was also demonstrated that the addition of hydrofluorocarbon solvent to polymer solution remarkably enhanced the formation of β‐phase crystalline structure of PVDF nanofiber. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 779–786, 2006

ABSTRACT:Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). In the present work, the additive effect of ionic fluorinated surfactants-anionic and cationic surfactants -on the diameter, morphology, and crystalline structure of PVDF nanofiber was investigated. The addition of ionic fluorinated surfactants is useful for the formation of bead-free homogeneous fiber. At a higher concentration of the ionic surfactants, thicker fiber was formed. In addition, the Fourier transform infrared spectroscopy and the wide angle X-ray diffraction measurements showed that the addition of both ionic fluorinated surfactants causes a complete change in conformation from the initial -phase of to the -phase of PVDF during ESD. A possible mechanism based on the interaction between the polymer and surfactant molecules during ESD is discussed.

The fine structure of poly(vinylidene fluoride) (PVDF) nanofiber prepared by electrospray deposition (ESD) has been investigated by wide angle X‐ray diffraction (WAXD) and infrared spectroscopy (IR). The β‐phase crystal was dominant in the crystalline region. The degree of crystallinity of 0.54 for the nanofiber, determined by Ruland's method, was almost identical to that for a melt pressed sheet of PVDF. The disorder parameter k was 4, which is significantly smaller than the value of 6 for the melt pressed sheet of PVDF. Molecular orientation along the fiber axis was observed by the polarized infrared spectra of the uniaxially aligned nanofiber. These results suggest that the PVDF nanofiber possesses a fiber structure which is by no means inferior to that of practical fibers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 558–563, 2008

Unoriented and highly oriented films of poly(octylthiophene) (POT) have been studied by optical-absorption measurements and Raman scattering. Optical absorption was analyzed using a vibronic model improved by the explicit evaluation of transition-matrix elements. The average conjugation length of POT at room temperature was estimated to be four thiophene rings. After stretch orientation, the ordered region in the material and the conjugation length in the ordered region increased. A clear dispersion and a strong anisotropy were observed for the Raman line of the amplitude mode, which is interpreted by the conjugation-length model.

ABSTRACT:The in situ optical absorption and fluorescence of poly(3-octylthiophene) (POT) upon electrochemical doping were studied. Fluorescence from the undoped POT was observed in the acetonitrile electrolyte. It was quenched by the electrochemical doping. The effect of a dopant molecule on the intensity change of the fluorescence is 7.5 times greater than the one for the optical absorption. Thus, the fluorescence quantum yield decreased after electrochemical doping.