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The formation of aggregates of a fraction of asphaltenes extracted from Brazilian crude oil was investigated by measuring the interfacial tension and kinematic viscosity of their solutions prepared in different solvents. The interfacial tension results indicate the existence of critical micelle concentration (CMC) levels of the asphaltenes in solvents with solubility parameters sufficiently different from those of the asphaltene tested. The kinematic viscosity measures revealed the formation of aggregates at concentrations above the CMC. The interfacial tension measures of asphaltenes in organic solutions, although infrequently mentioned in the literature, were used to calculate the molar mass, permitting the comparison of various molar masses attributed to the asphaltenes in the form of aggregates.

The influence of the solveny medium on the aggregation of asphaltene macromolecules and determination of their molar mass