Colloidal Particle-Induced Microstructural Transition in Cellulose/Ionic Liquid/Water Mixtures

Abstract

The role of colloidal particles in enhancing the mechanical and thermal properties of liquid crystalline (LC) gels formed in microcrystalline cellulose/1-allyl-3-methylimidazolium chloride/water mixtures is experimentally investigated by means of rheology and polarized optical microscopy (POM). The overshoot in loss modulus and increase in the melting temperature of LC domains as observed in differential scanning calorimetry signal a stronger interaction of cellulose with both hydrophobic polystyrene and hydrophilic silica nanoparticles which in turn point to considerable amphiphilic nature of cellulose. The aggregation of nanoparticles observed by POM and the rheological behavior point to the development of a sample-spanning network of cellulose− nanoparticle clusters during the sol−gel transition with an increase in concentration of water. Furthermore, the LC gels obey Chambon−Winter (CW) criterion, indicating a self-similar gel network, except at very high particle loadings. Moreover, the LC domains show a temporal evolution into a space-spanning network of cellulose spherulites. The evolution process largely depends on the particle concentration, with highly loaded samples showing quicker evolution, which leads to a violation of the CW criterion. Furthermore, the temperature-induced microstructural transition (with and without shear) is also examined.

Advances in the use of microgels as emulsion stabilisers and as a strategy for cellulose functionalisation

“…As discussed previously (''Top-Down Approaches'' section), like other polymer microgels the nature and morphology is highly dependent on the properties of the macrogel, which in turn is affected by the amount of cellulose dissolved and the method and conditions of coagulation (applied shear force, temperature, anti-solvent, etc.) (Li et al 2009;Fan et al 2017;Rajeev and Basavaraj 2019).…”