Synthesis and solution rheology of poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)

Abstract

Poly([stearyl methacrylate]-stat-[2-(dimethylamino) ethyl methacrylate]) was synthesised through radical polymerisation using 1,1-diphenyl ethylene (DPE) as a molecular weight controlling agent. The amino groups were further quaternised into a cationic form in order to increase water solubility. Solubility of the polymers in water and a mixed solvent was studied with rotational rheometry. The resulting poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)] was soluble in water when the amount of stearyl methacrylate (SMA) in the polymer was less than 17 mol%. At higher SMA content, solubility strongly decreased but could be improved by using an organic co-solvent. Viscosity of the SMA-based statistical co-polymers is strongly dependent on polymer composition but solvent quality also has an influence, and the fluidic character can be either Newtonian or shear-thinning, or a weak gel can be formed. Concentration dependence behaviour deviates from that of typical polyelectrolytes. SMA polymers retain low viscosity up to rather high concentrations, but above a certain limiting concentration, the viscosity rapidly increases. This phenomenon is stronger with a higher amount of hydrophobic side-chain. At high co-polymer concentrations no entanglement formation was observed, and rheological behaviour indicates that SMA segments form aggregates in water solution.