Morphological and thermal properties of optimized electrospun cellulose acetate nanofibres during deacetylation in different pH values

Abstract

The aim of this study is to investigate morphology, molecular structure and thermal behavior of optimized cellulose acetate nanofibrous mats during deacetylation reaction in both basic and acidic environments. Firstly, the polymer concentration, applied voltage, flow rate and syringe needle tip-collector distance have been optimized via a response surface methodology. This optimization of the above independent variables leads to obtain a uniform and smooth morphology for cellulose acetate nanofibrous samples with a minimum average diameter of 166.2 nm. Afterward, the effect of basic and acidic environments on the morphologies, functional groups changes on the surface of the samples and their thermal behaviors have been studied by using scanning electron microscopy (SEM), Fourier transformed infra-red (FTIR)spectroscopy and differential scanning calorimetry (DSC) respectively. The FTIR results show that a deacetylation reaction occurs in nanofibrous samples treated with KOH solution as compared to those samples treated with HCl solution. Due to the altering functional groups in the chemical structure, cellulose acetate nanofibres are converted to cellulose with a semi-film like shape. The SEM micrographs confirm these results obtained from FTIR spectra. DSC thermograms reveal different values at melting point of the samples before and after immersion of the samples into the both environments. Moreover, some changes in crystallization appear within the molecular structure of the samples during solidification.