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Miscibility and interactions of rheology improvers based on functional polymethacrylate in toluene solutions

In this work, miscibility and molecular interactions of poly(dimethylaminoethyl methacrylate) (PDMAEMA) and series of homologous poly(n-alkyl methacrylates), namely: poly(methyl methacrylate), poly(hexyl methacrylate), poly(dodecyl methacry-late) and poly(octadecyl methacrylate), as well as between PDMAEMA and poly (ethylene-co-propylene) (EPC) or polystyrene (PS), were investigated by the dilute solution viscometry, in toluene as a model solvent for mineral base oil at 30 ° C. The specific, reduced and intrinsic viscosities as well as viscometric interaction parameters were determined for binary, polymer / toluene, and ternary, PDMAEMA / (PAMA or EPC or PS) / toluene systems. The PDMAEMA / (PMMA or PHMA or PODMA or EPC) investigated polymer / polymer pairs showed the negative viscometric interaction parameter values (Db12 < 0), calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations. Therefore, these polymer mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and structure. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter, where the interaction parameter values Db12 > 0. Investigated polymers are widely used as lubricating mineral oil rheology modifiers, that is viscosity index improvers, dispersants and pour point depressants. Thus, interaction and miscibility of the corresponding polymer mixture additives are important factors for the formulation of lubricants, such as motor oils.

dilute solution viscometry; miscibility; poly(dimethylaminoethyl methacrylate); poly(alkyl methacrylate); polystyrene; poly(ethylene-co-propylene)

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