Mihkel Viirsalu

Influence of Preparation Process on Morphology and Conductivity of Carbon Black-Based Electrospun Nanofibers

In this work, three different methods of preparation of polyacrylonitrille (PAN) with carbon black (CB) solutions further used in electrospinning for producing conductive fiber mats are discussed. CB is used as conductive filler. Content of CB in polymer matrix is varied, CB/PAN = 1/2, 1/1, and 3/2. The solution properties and obtained fiber morphology are analyzed. The effect of preparation on fiber morphology and conductivity is analyzed, as well as the effect of sonication on solution properties, morphology, and conductivity of PAN+CB samples.

Impact of 1-butyl-3-methylimidazolium chloride on the electrospinning of cellulose acetate nanofibers

ABSTRACT Additives like ionic liquids (ILs) have proven to be excellent materials useful in improving the electrospinnability and conductivity of both synthetic and biopolymers. The aim of this study is to investigate the effect of 1-buthyl-3-methylimidazolium chloride [BMIM]Cl on the electrospinnability of cellulose acetate (CA). The results showed that [BMIM]Cl has the greater effect on viscosity and conductivity of the spinning solution while the morphology of the nanofibers significantly improved as the concentration of the IL increases from 0% to 12% (v/v) of [BMIM]Cl. To understand the interaction between CA and [BMIM]Cl, Fourier-transform infrared spectroscopy (FTIR) has been used. Observations by scanning electron microscopy (SEM) suggested that [BMIM]Cl significantly altered the morphology of the CA nanofibers and 12% (v/v) of [BMIM]Cl would be an ideal concentration producing uniform fibers with a mean diameter of 180nm. In addition, the membranes showed a significant increase in conductivity (from 0 to 2.21 × 10−7S/cm) as the concentration of ionic liquid increases up to 12% (v/v) that indicates a successful loading of IL inside the nanofibers.

One-step carbon nanotubes grafting with styrene-co-acrylonitrile by reactive melt blending for electrospinning of conductive reinforced composite membranes

ABSTRACT Aim of this research was to electrospin conductive composite membrane of styrene-co-acrylonitrile (SAN) reinforced with carbon nanotubes (CNTs). To improve electrical conductivity of final membrane ionic liquid (IL) was used. For better dispersion of CNTs in SAN matrix one-step reactive melt blending method for grafting of SAN onto CNTs was developed. Influence of SANm-g-CNTs on solutions properties was studied and compared to solutions with ungrafted CNTs and carboxyl group functionazed CNTs (CNT-COOHs). Combination of IL and SANm-g-CNTs increase in to orders of magnitude SAN membrane tensile stress and modulus. Electrical conductivity of obtained membranes achieved the level of semi-conductor materials.

Synthesis of Polymerizable Ionic Liquid Monomer and Its Characterization

The polymerizable monomer of 1-(6-hydroxyhexyl)-3-methylimiadazolium bromide ionic liquid (IL) was synthesized. The thin layer chromatography tests were conducted at each step to verify the reactions. It was observed that the ionic liquid compound formed after 48 hours though confirmed the presence of starting materials. A high viscous transparent liquid was extracted and believed to be formed of 99% yielding of ionic liquid. Apart from that, the synthesis of ionic liquid was also performed using microwave treatment and heating to stimulate the reaction. Surprisingly, it was observed that the reaction was taking place within a fraction of second when the synthesis process was conducted with microwave treatment. In the second step, esterification IL with methacryloyl chloride was done to obtain monomer of polymerizable ionic liquid (m-PIL). The final product was a high viscous yellowish liquid.