Perfluorooctanoic acid-mediated self-assembly behaviour of linear and star block copolymers: the impact of intermolecular interactions on polymer micelles

Abstract

In this study, we present results from high-sensitivity differential scanning calorimetry (HSDSC), dynamic light scattering (DLS), small-angle neutron scattering (SANS), and computational simulation performed for understanding the micellization and micelle morphology of two EO–PO block copolymeric surfactants, namely, the linear triblock copolymer Pluronic® F127 and the star block copolymer Tetronic® T1107 (both with 70% PEO content), in the presence of perfluorooctanoic acid (PFOA). Increasing the concentration of PFOA in aqueous solutions of both copolymers resulted in a significant reduction in the critical micellization temperature (CMT), as inferred from the calorimetric findings. Scattering experiments revealed intriguing results, indicating that the micelle radius (R_c, R_hs) and aggregation number (N_agg) of polymeric micelles increased with increasing PFOA concentration. The addition of PFOA did not alter the morphology of the micelles; however, comparing the correlation peaks in SANS suggested that the distance between the spherical micelles decreased as the PFOA concentration increased. Thus, the outcome of this study helps to fine-tune the performance-based properties of these widely used polymeric surfactants with a fluorinated hydrophobic additive.