Fabrication of agar/biopolymer blend aerogels in ionic liquid and co-solvent mixture

In the present study, a biopolymer (cellulose, rice starch or zein protein) was dissolved in the ionic liquid (l-butyl-3methylimidazolium chloride) and co-solvent (dimethyl sulfoxide) mixture (1:1 weight ratio), and then blended with the agar solution, followed by gelation at low temperature. The blends were soaked and shaken in 250 mL distilled water, washed and freeze-dried. The agar/biopolymer contents were varied as 1:1, 1:1.5 and 1:2 weight ratios. The bulk densities, melting point temperatures (Tm), FTIR spectra, surface morphologies, surface areas and pore size diameters of the blend aerogels were determined and characterized. The lowest bulk density (25.69 mg cm-3 ) was obtained for agar/rice starch, at a 1:2 weight ratio. DSC thermograms indicated depression in Tm, with the addition of biopolymers. FTIR spectra showed the presence of functional groups of blend aerogels components. SEM micrographs of blend aerogels indicated the presence of pores in their internal surface. The BET surface areas and pore size diameters of the blend aerogels (1:2 weight ratio) ranged from 371 to 478 m2 g-1 and from 34 to 63 nm, respectively. This study led to the conclusion that the mixture of l-butyl-3-methylimidazolium chloride and dimethyl sulfoxide could be used as a blend medium for the fabrication of agar/biopolymer blend aerogels.