Modification of acrylonitrile/acrylic acid copolymer films and fibers by dendrigraft formation

Abstract

Samples of film, wet-and electro-spun fibers and powder were prepared from acrylonitrile/acrylic acid copolymer, with their specific surface areas being considerably different. We attempted to alter the properties of the samples by increasing the amount of carboxylic acid groups on the surfaces through the formation of dendritic structures. Dendritic molecules were grown by a reaction between the carboxylic acid groups of acrylic acid, activated by dicyclohexylcarbodiimide, and hydroxyl groups of citric acid. Products were analyzed using Fourier transform infrared and NMR spectroscopy, optical microscopy, scanning electron microscopy and density measurements. It was found that with an increase of the specific surface area, the percentage conversion increased indicating that the topochemical reactions were prominent. The density of electro-spun fibers was the greatest indicating the most compact structure. With an increase of step numbers of dendrigraft formation the density reached a minimum which points to the formation of nanoscale voids in the deposited dendritic structure.

Dendrigraft with citric acid on acrylonitrile/acrylic acid copolymer electrospun fibres

“…Figure shows that the percentage conversion of the reactions decreases with increasing generation number and increasing AA content of the copolymers. In comparison with previous work, where AA contents were 5 mol%, decreasing the AA content to less than 5 mol% results in a greater conversion on ES‐fibres.…”

“…There are sharp peaks at 1727 cm −1 for G 0 and at 1735 cm −1 for G 1 , G 2 , G 3 and G 4 due to CO stretching. The FTIR spectra for G 1 to G 4 show a band at 930 cm −1 related to the formation of hydrogen‐bonding interactions between the ester groups of CA and the acidic hydrogen atoms of CA, which is not observed for the G 0 samples . The spectra of other dendrigrafted ES‐fibres which are similar to that for the 10% AA spectra are not shown here.…”

“…The integrated intensities of CH 2 signals of CA and P(AN/AA) in 1 H NMR spectral analysis were used to calculate the percentage conversion, as described previously . Figure shows that the percentage conversion of the reactions decreases with increasing generation number and increasing AA content of the copolymers.…”

“…Dendrigrafts were synthesized on the ES‐fibres according to the procedure described previously . Several consecutive reaction steps were carried out.…”

Citric acid-modified acrylic micro and nanofibers for removal of heavy metal ions from aqueous media

“…To increase the reactivity of HPAN with CA, HPAN fibers were reacted with N,N´-Dicyclohexylcarbodiimide (DCC) [17,18]. HPAN fibers were added to a flask containing a solution of DCC in THF and dioxane (50:50 v/v).…”