Phase Behaviour of Hydroxypropyl Cellulose/ Polyacrylamide Gels

Summary : Polysaccharide‐based materials have gained nowadays a great importance in many fields of industry, e.g., in the pharmaceutical industry. Some characteristics of such compounds are their non‐toxicity and the presence of a lower critical solution temperature (LCST) and/or an upper critical solution temperature (UCST). This work presents results on the synthesis and characterization of composites from hydroxypropyl cellulose (HPC) and polyacrylamide (PAAm). The ratio of HPC/PAAm was varied as well as the concentration of the crosslinker and the pH value of the reaction mixture. The compounds prepared were characterized by means of Fourier Transform Infrared spectroscopy (FTIR) and turbidity measurements. FTIR spectroscopy showed the presence of the main structural features of the precursors in the gels. The turbidity measurements of the gels in water showed the presence of a LCST in all samples. The LCST decreased when the quantity of HPC was increased in the gel and diminished also with increasing quantities of crosslinker and pH. The turbidity measurement showed the presence of an UCST when the concentration of the polymer was higher than 1% (w/w). This phenomenon is caused by the presence of the PAAm, which acted as precipitant and influenced over the entropy of the system and provoked phase separation.