The micellar growth of quaternary ammonium Gemini surfactants containing methylene group spacer (referred to as C₁₂-s-C₁₂, 2Br) in inorganic salt (NaBr) media was investigated by using dynamic light scattering. The size of micelles increases with increasing salt concentration or decreasing temperature or decreasing the length of spacer chain. The enlarged micelles have a shape of prolate ellipsoid or rod. Based on these mean hydrodynamic radius (R_h) measurements, values of the thermodynamic parameter K governing the sphere to rod transition were determined. Numerical values of enthalpy and entropy change for this transition were deduced from the linear plot of ln K vs. 1/T. The novel micellar growth of C₁₂-2-C₁₂, 2Br was discussed. The distribution of micelle size was analyzed by using non-negatively constrained least square (NNLS) algorithm.

Key words: Gemini surfactant, mean hydrodynamic radius, dynamic light scattering, micellar growth