Effect of amphiphilic and non-amphiphilic polymers on micellar behaviour of nonionic surfactant Triton X-100

Cloud point (CP), dynamic light scattering (DLS) and small angle neutron scattering (SANS) have been used to study polymer/surfactant interactions involving Triton X-100 (TX-100) with nonionic polymers, namely, polypropylene glycol (PPG), polyethylene glycols (PEGs) as well as triblock copolymers PEG-PPG-PEG and PPG-PEG-PPG. PEG molecules wrap around TX-100 micelles and do not change the size of the micellar core. While PPG does not alter the micelle size at ambient temperature, it drastically increases the size at elevated temperature. On the other hand, triblock copolymers with different PEG/PPG ratios and molecular weights show unusual effects on the cloud point/micellar behaviour of TX-100 compared to PEG and PPG. In absence of the polymer, TX-100 micelles are ellipsoidal at 30 degrees C but the ellipticity of the micelles increases significantly at higher temperature (50 degrees C). Ellipsoidal micelles of TX-100 transform into spherical micelles on addition of hydrophilic triblock copolymers (F88, F108). Low molecular weight hydrophobic triblock copolymers such as L61, L81 and 25R4 offer considerable micellar growth at high temperature. Conversely, micellar growth was not found in the system containing TX-100 with high molecular weight and very hydrophobic L101 and L121 copolymers, even at a higher temperature. These results are discussed in terms of the penetration of polymer molecules into TX-100 micelles. (C) 2015 Elsevier B.V. All rights reserved.