Search for: All records

Ion transport in solid polymer electrolytes is crucial for applications like energy conversion and storage, as well as carbon dioxide capture. However, most of the materials studied in this area are petroleum-based. Natural materials (biopolymers) have the potential to act as alternatives to petroleum-based products and, when derived with ionic liquid (IL) functionalities, present a sustainable alternative for conductive materials by offering tunable morphological, thermal, and mechanical properties. In this study, a series of IL-functionalized cellulose derivatives with variations in pendant alkyl chain length, counteranions, and degrees of substitution were synthesized in order to explore structure-property relationships. Emphasis was placed on investigating morphological, thermal, and ionic conductivity changes, hypothesizing that materials synthesized with longer alkyl chains would exhibit increased backbone-to-backbone spacing, thereby lowering the glass transition temperature, and enhancing ionic conductivity. A variety of characterization techniques were used for this investigation, including nuclear magnetic resonance spectroscopy (NMR), elemental analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray scattering, and dielectric relaxation spectroscopy (DRS). The findings reveal a link between longer alkyl chain lengths, expanded backbone-backbone spacing, and side chain interdigitation. Within each set of samples, heightened ionic conductivity was observed with the introduction of bulkier, less coordinating anions, underscoring the significant influence of counteranion size. 

Dual ionic liquid-substituted cellulosic materials were prepared by coupling a series of alkyne-terminated imidazoles with variable carbon spacer with azide-functionalized cellulose, followed by quaternization and anion exchange. All three of the [NTf2]-bearing cellulosic materials exhibited Tg values below zero and could be cast as flexible films, which exhibited stress at break values exceeding 2.3 MPa with strain at break values up to 252%. X-ray scattering analyses indicated the amorphous nature of the cellulosic materials with three scattering peaks observed, from high-to-low q, corresponding to the amorphous halo, anion-to-anion distance, and the distance between ion aggregates, respectively. The highest degree of ionic aggregation was found to exist in the CELL-C12-NTf2 material, presumably due to the longer alkyl tethers causing more uniformity in the interaggregate spacing. The conductivity of the films was found to be on the order of 10−5−10−6 S/cm at 30 °C. A slower increase in conductivity with temperature was observed for systems where ionic aggregation was the strongest. 

Blended biocomposites created from the electrostatic and hydrophobic interactions between polysaccharides and structural proteins exhibit useful and unique properties. However, engineering these biopolymers into applicable forms is challenging due to the coupling of the material’s physicochemical properties to its morphology, and the undertaking that comes with controlling this. In this particular study, numerous properties of the Bombyx mori silk and microcrystalline cellulose biocomposites blended using ionic liquid and regenerated with various coagulation agents were investigated. Specifically, the relationship between the composition of polysaccharide-protein bio-electrolyte membranes and the resulting morphology and ionic conductivity is explored using numerous characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray scattering, atomic force microscopy (AFM) based nanoindentation, and dielectric relaxation spectroscopy (DRS). The results revealed that when silk is the dominating component in the biocomposite, the ionic conductivity is higher, which also correlates with higher β-sheet content. However, when cellulose becomes the dominating component in the biocomposite, this relationship is not observed; instead, cellulose semicrystallinity and mechanical properties dominate the ionic conduction.