Ionic Liquid (1-Ethyl-3-methylimidazolium Acetate) Plasticization of Chitosan-Based Bionanocomposites

Abstract

The structure and properties of different biopolymer composites based on chitosan and chitosan/carboxymethyl cellulose (CMC) are governed by multiple structure–property relationships associated with different phase interactions. Plasticization of these matrices with ionic liquid 1-ethyl-3-methylimidazolium acetate ([C 2 mim][OAc]) played a dominant role, increasing the mobility of biopolymer chains as well as ions and associated dipoles but reducing biopolymer chain interactions, crystallinity, and thermal stability. These structural changes led to higher matrix ionic conductivity, shorter electrical relaxation time, and greater matrix ductility. The inclusion of graphene oxide (GO) and reduced GO (rGO) also influenced the structure and properties of these bionanocomposites by disrupting the biopolymer hydrogen bonding and/or polyelectrolyte complexation (PEC) and interacting with [C 2 mim][OAc]. The impact of GO/rGO was more evident for 20 wt % [C 2 mim][OAc], such as increased crystallinity and thermal stability of chitosan. PEC was hindered with excess (40 wt %) [C 2 mim][OAc] added and further hindered again when rGO was included. This study shows that the structure and properties of bionanocomposites are not just determined by the surface chemistry of GO/rGO but can also be influenced by multiple interactions involving plasticizers such as ILs and additional biopolymers.

Cooperative Effects of Cellulose Nanocrystals and Sepiolite When Combined on Ionic Liquid Plasticised Chitosan Materials

“…Again, the inclusion of both CNCs and SPT was effective at suppressing re-crystallisation of the biopolymers, similar to that observed for A/CS-F. BE2/S-F and BE2/C-F exhibited a similar XRD pattern as that for BE2-F [29]. The IL facilitates biopolymer re-recrystallisation [29]. For BE2/C-F, the peaks at 13.5° and 10° 2θ were moderately more intense, suggesting CNCs further assisted the re-crystallisation of the IL-plasticised biopolymers.…”

“…Compared with B-F which was much less crystalline than A-F [13], B/S-F, B/C-F, and B/CS-F were even more amorphous. Again, the inclusion of both CNCs and SPT was effective at suppressing re-crystallisation of the biopolymers, similar to that observed for A/CS-F. BE2/S-F and BE2/C-F exhibited a similar XRD pattern as that for BE2-F [29]. The IL facilitates biopolymer re-recrystallisation [29].…”

“…In this regard, there may be interaction between CNCs and SPT, which combined results in greater steric hindrance limiting chain movement for re-crystallisation. Compared with AE2-F [ 29 ], AE2/S-F, AE2/C-F, and AE2/CS-F exhibited an unchanged XRD pattern, indicating that the inclusion of CNCs and/or SPT did not impact chitosan re-crystallisation.…”

“…The suffix “F” indicates the processed samples were in film form. A-F and B-F (without plasticiser or nano-additives) [ 13 ] and AE2-F and BE2-F (plasticised by [C 2 mim][OAc] at 20% but without nano-additives) [ 29 ], prepared in the same way, were reported previously and were compared with throughout the discussion section of this paper.…”

A Concise Review on the Physicochemical Properties of Biopolymer Blends Prepared in Ionic Liquids

“…Cellulose in the form of pulp [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ], linter [ 9 , 10 ], microgranular [ 11 , 12 , 13 ], microcrystalline [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ], and fabric [ 29 ] were usually used as raw materials for preparing biopolymer blends. On top of that, other biopolymers such as agarose [ 30 ], alginate [ 31 , 32 ], chitin [ 10 , 17 , 26 , 27 , 31 , 33 ], chitosan [ 1 , 4 , 5 , 7 , 29 , 30 , 34 , 35 , 36 ], chondroitin sulfate [ 37 ], collagen [ 24 , 32 ], keratin [ 6 , 8 , 21 ], lignin [ <...>…”