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- Filling in the voids of electrospun hydroxypropyl celulose network: dielectric investigationsPublication . MANAILA MAXIMEAN, DOINA; Danila, Octavian; Ganea, Constantin Paul; Almeida, Pedro L.Here we describe an organic electro-optic device, obtained using electrospun hydroxypropyl cellulose (HPC) polymer fibres and nematic liquid crystals (LC). Its working mechanism is similar to that of a classic polymer-dispersed liquid crystal (PDLC) device. The scanning electron microscopy of the HPC deposited fibres shows a mat of fibres with diameters in the nano and micron size range. Dielectric spectroscopy measurements allow the determination of the dependence of the dielectric constant and electric energy loss on frequency and temperature as well as the determination of the activation energy. The electro-optic study shows a very good optical transmission curve, with an “on”-“off” switching voltage of less than 1V/μ m.
- Electrical properties of a liquid crystal dispersed in an electrospun cellulose acetate networkPublication . MANAILA MAXIMEAN, DOINA; Danila, Octavian; Almeida, Pedro L.; Ganea, Constantin PaulElectro-optical devices that work in a similar fashion as PDLCs (polymer-dispersed liquid crystals), produced from celulose acetate (CA) electrospun fibers deposited onto indium tin oxide coated glass and a nematic liquid crystal (E7), were studied. CA and the CA/liquid crystal composite were characterized by multiple investigation techniques, such as polarized optical microscopy, dielectric spectroscopy and impedance measurements. Dielectric constant and electric energy loss were studied as a function of frequency and temperature. The activation energy was evaluated and the relaxation time was obtained by fitting the spectra of the dielectric loss with the Havriliak–Negami functions. To determine the electrical characteristics of the studied samples, impedance measurements results were treated using the Cole–Cole diagram and the three-element equivalent model.