LOW HYDROPHOBICALLY-MODIFIED POLY(ACRYLIC ACID) STABILIZING MACROEMULSIONS - RELATIONSHIP BETWEEN COPOLYMER STRUCTURE AND EMULSIONS PROPERTIES

Low hydrophobically modified (with dodecylamide chain) linear poly(acr ylic acid) sodium salts (LHMPAANa) of various degrees of grafting (tau ) and molecular weights were synthesized and used as emulsifiers of th e n-dodecane/water (NaNO3 10(-3) M) system. Stability and how properti es of the resulting n-dodecane in water emulsions (dispersed phase vol ume fraction = 0.5) were investigated as a function of tau (tau = 0 to 10% in mel), molecular weight (5000, 50,000, and 150,000 g/mol) and p olymer concentration (0 to 10%). It was clearly shown that viscosifica tion (via an associating mechanism of LHMPAANa) of the external phase of emulsions is a key factor in explaining dispersion breakdown. Howev er, a complete description of the phenomenon could not be achieved wit hout considering the adsorption of the polymer at the liquid-liquid in terface which depends closely on tau but not much on molecular weight. The molecular weight effects were found to be restricted to the visco sification of the outer phase. (C) 1998 Academic Press.