The effect of salts on mixtures of the lyotropic mesogen hydroxypropyl cellulose with water and with coiled polymers

The phase behavior of hydroxypropyl cellulose (HPC) in aqueous systems is affected differently by thiocyanate salts compared with other salts. Thiocyanate salts tend to enhance solubility as evidenced by a higher cloud point temperature. In more concentrated aqueous solution of HPC, inclusion of {dollar}rm NHsb4SCN{dollar} stimulates its chiral nematic mesophase and leads to a substantial increase in pitch. Results suggest that inclusion of thiocyanates alters the solution properties of these systems by breaking of water structure-salting-in effect.; Concomitant with its salting-in effect, the inclusion of thiocyanate increases the solubility of some other water soluble polymers, such as poly(ethylene glycol)(PEC) and poly(acrylic acid) (PAA). The results from measurements of viscosity and cloud points show that the HPC/PEG/H{dollar}sb2{dollar}O system displays features of immiscibility and HPC/PAA/H{dollar}sb2{dollar}O present phase separation because of formation of a polymer/polymer complex Inclusion of LiSCN makes these mixtures miscible by increasing the mutual solubility of HPC/PEG blends. and through dissociation of the HPC and PAA blend.; For more concentrated mixtures, the HPC/PEG/H{dollar}sb2{dollar}O system displays immiscibility between the HPC mesophase and PEG isotropic phase. Microscopical observations and D-NMR suggest that the immiscibility is mitigated by introduction of LiSCN. For the HPC/PAA/H{dollar}sb2{dollar}O system, mesophase formation is inhibited by strong complexation between the polymers. The inclusion of LiSCN contributes to weakening the polycomplexes, and an anisotropic monophase is thus observed by microscopy. A miscible mixture containing rigid and flexible polymers can be an interesting subject for applications in chemical engineering and material science.