The micellar structural transition in cationic amphiphiles, viz.alkyltrimethylammonium bromides (C₁₂-,C₁₄-, C₁₆- and C₁₈TABr), hexadecylpyridinium bromide (C₁₆PyBr) and hexadecyltriphenylphosphonium bromide (C₁₆TPPBr) in the presence of polyoxyethylene dodecyl ethers (C₁₂E_n, n = 3–8) was studied using
viscosity and scattering (dynamic light scattering (DLS) and small angle neutron scattering measurements (SANS)) techniques. Aprogressive growth in micellar size was observed upon the addition of C₁₂E_n particularly when n≤5 and C₁₂E₃ was found to be the most effective in promoting the micellar growth attributed to increasing hydrophobicity of surfactants. These results are well supported by SANS measurements which reveal increase in major axis of the ellipsoidal micelle with increase in C₁₂E₃ concentration up to 20mM, leading to large elongated micelles, above which the size remained nearly constant. Increased effectiveness of lipophilic nonionic surfactant is discussed in light of electrostatic and hydrophobic forces operating in solution, which are responsible for micellar growth process.