Effect of Cationic Polyelectrolyte on the Flow Behavior of Hydroxypropyl Methyl Cellulose/Polyacrylic Acid Interpolymer Complexes

Association of polyacrylic acids and nonionic polymers in solutions via hydrogen bonding results in formation of novel polymeric materials. These complexes are novel individual compounds and their properties are entirely different from the properties of their component polymers. In this study, the effects of a cationic polyelectrolyte (polyethylenimine, PEI) on the interpolymer complexation of hydroxypropyl methyl cellulose (HPMC) with polyarcylic acid (PAA) in aqueous media were studied. Results showed that at low pH, interpolymer complex (IPC) formation was observed between HPMC and PAA at a 3:0.5 polymer ratio. Under basic conditions, the viscosity of the IPC increased accompanied with the transition from coiled structure to an extended conformation of associates. Addition of PEI to the same system caused some structural changes in the polymer solution mixtures depending on the pH of the system. PEI worked as a destructive agent for the HPMC/PAA interpolymer complexes and associates. This behavior was attributed to the complex formation between PEI and HPMC via hydrogen bonding.