Microheterogeneity and Microviscosity of F127 Micelle: The Counter Effects of Urea and Temperature

Abstract

F127 is the most widely studied triblock copolymer and due to the presence of very long polypropylene oxide (PPO) and polyethylene oxide (PEO) groups, F127 micelle has different microenvironments clearly separated into core, corona, and peripheral regions. Urea has been known to have adverse effects on the micellar properties and causes demicellization and solvation; on the other hand, rise in temperature causes micellization and solvent evacuation from the core and corona regions. In the present study, we have investigated the microheterogeneity of the core, corona, and peripheral regions of the F127 micelle using red edge excitation shift (REES) at different temperatures and urea concentrations and correlated the effect of both on the micellar system. It was found that the temperature counteracts the effect of urea and also that the counteraction is more prominent in the core region with respect to corona, and the peripheral region is least affected. Also, the core and corona regions are very much heterogeneous, while the peripheral region is more of a homogeneous nature. Using time-resolved fluorescence anisotropy, we found that the microviscosity within the micelles vary in the order of core > corona > peripheral region, and urea has a general tendency to reduce the microviscosity, especially for core and corona regions. On the other hand, rise in temperature initially increases and then decreases the microviscosity throughout, and at elevated temperatures the effect of urea is being dominated by the effect of temperature, thereby establishing the counter effects of temperature and urea on the F127 micellar system.

How does bile salt penetration affect the self-assembled architecture of pluronic P123 micelles? – light scattering and spectroscopic investigations

“…The corresponding anisotropy decays are shown in Fig. [65][66][67] By this observation we can conclude that the core region of the P123 micelle is more affected by the bile salt penetration in comparison to the corona region of the micelle. The gradual decrease in the rotational time of both C153 and C480 with the penetration of bile salts into the P123 micelle indicates that there is a net increase in the hydrophilicity and polarity surrounding the probe molecules in the bile salt-P123 mixed micelle.…”

Urea-based gemini surfactants: Synthesis, aggregation behaviour and biological activity

“…Urea significantly affects the aggregation properties and microstructure of nonionic micelles consisted of triblock copolymers [10] or sugar-based surfactants (glucopyranosides and maltopyranosides) [11]. The increased aggregation behaviour (vesicles formation, organogelators) was confirmed for fluorinated amphiphilic urea derivatives [12,13].…”

Self‐assembly of telechelic polymers bearing adamantane groups via host‐guest inclusion complexes with cyclodextrin polymer

“…After incorporation of the cyclodextrin host molecules, the flowerlike micelles of Ada-F127-Ada as first compressed by inclusion complexation and further increased with rise in temperature. [44] At the turning point about of 20 C, the temperature-enhanced supramolecular interaction of the host-guest was destroyed and the structure of F I G U R E 6 1 H NOESY NMR spectra of Ada-PAA-SH/P(β-CD) (A) and Ada-F127-Ada/P(β-CD) (B) inclusion complexes in water after frozen dried [Color figure can be viewed at wileyonlinelibrary.com] micelles collapsed due to the increasing CMC, [47] the micelles size distribution also became broad (seeing Figure S6).…”