Influence of urea on single and mixed micellar systems of Tetronics®

Here we report micellar and micellization characteristics of single and mixed Tetronics (R) altered by the presence of urea using high sensitivity differential scanning calorimetry (HSDSC) and small angle neutron scattering (SANS). Three Tetronics (R) with almost identical polypropylene oxide (PPO) blocks but variable polyethylene oxide (PEO) blocks viz. T1301, T1304 and T1307, were chosen for studying their solution behavior in aqueous urea (0-8 M) solutions. In the case of single micellar systems, the three copolymers showed markedly different behavior.T1301 being most hydrophobic forms vesicular structures at ambient temperature, T1304 with moderate hydrophobicity forms micelles with low polydispersity while very hydrophilic T1307 exhibits high polydispersity and occur as unimers, loose micelles and clusters. The addition of urea has a disruptive effect on all the three copolymers; smaller vesicles in T1301, smaller micelles with enhanced polydispersity in T1304 and T1307 completely demicellizes to unimers and clusters as evidenced by SANS. A similar trend has also been noticed for mixed micelles. However, the phase separation temperature/critical micelle temperature (CMT) of the co-polymers in binary mixtures are slightly lower as compared to the copolymer solutions of individual block copolymers in the presence of 8 M urea. HSDSC measurements revealed decreased enthalpy of micellization (Delta H) and increased CMT in the presence of urea suggesting enhanced solubility of the copolymer and consequently delayed micellization. (C) 2017 Elsevier B.V. All rights reserved.