Agarose processing in protic and mixed protic–aprotic ionic liquids: dissolution, regeneration and high conductivity, high strength ionogels

Abstract

We have shown that low viscosity alkyl or hydroxyalkyl ammonium formate (ILs) can dissolve agarose, and higher dissolution can be achieved in the mixed, alkyl or hydroxyalkyl ammonium + imidazolium or pyridinium ILs. The polarity parameters α, β, π*, E_T(30) and E_T^N of these IL systems were measured to explain their dissolution ability for agarose. Dissolved agarose was either regenerated using methanol as a precipitating solvent or ionogels were formed by cooling the agarose–IL solutions to ambient temperature. Exceptionally high strength ionogels were obtained from the agarose solutions in N-(2-hydroxyethyl)ammonium formate or its mixture with 1-butyl-3-methylimidazolium chloride. Regenerated material and ionogels are characterized for their possible degradation/conformational changes and gel properties (thermal hysteresis, strength, viscoelasticity and conductivity) respectively. A high strength, high conducting ionogel was demonstrated to be able to build an electrochromic window. Such ionogels can also be utilized for other soft matter electronic devices and biomedical applications.