Spontaneous Vesicle Formation in a Block Copolymer System

Cellulose nanocrystal and Pluronic L121-based thermo-responsive composite hydrogels

Cellulose nanocrystal (CNC) is a promising sustainable material with its biocompatibility, high aspect ratio, and mechanical strength. CNC-based systems have potential applications in various fields including biosensors, packaging, coating, energy storage, and pharmaceuticals. However, turning CNC into smart systems remains a challenge due to the lack of stimuli-responsiveness, limitation in compatibility with hydrophobic matrices, and their agglomeration tendency. In this work, a thermo-responsive nanocomposite system is constructed with CNCs and polymersome forming Pluronic L121 (L121), and its phase behavior and mechanical properties are investigated in detail. Two different CNC concentration (4 % and 5 %) is studied by changing the L121 concentration (1-20 %) to understand the effect of unimers and polymersomes on the CNC network. At dilute L121 concentrations (1-5 %), the composite system becomes softer but more fragile below the transition temperature. However, it becomes much stronger at higher L121 concentrations (10-20 %), and a gel network is obtained above the transition temperature. Interestingly, the elastically reinforced CNC gels exhibit greater resistance to microstructural breakdown at large strains due to the soft and deformable nature of the large polymersomes. It is also found that the gelation temperature for hydrogels is tunable with increasing L121 concentration, and the nanocomposite hydrogels displayed thermo-reversible rheological behavior.

Aqueous Two-Phase Systems within Selectively Permeable Vesicles

An aqueous two-phase system (ATPS) encapsulated within a vesicle organizes the vesicle core as two coexisting phases that partition encapsulated solutes. Here, we use microfluidic technologies to produce vesicles that efficiently encapsulate mixtures of macromolecules, providing a versatile platform to determine the phase behavior of ATPSs. Moreover, we use compartmentalized vesicles to investigate how membrane permeability affects the dynamics of the encapsulated ATPS. Designing a membrane selectively permeable to one of the components of the ATPS, we show that out-of-equilibrium phase separations formed by a rapid outflow of water can be spontaneously reversed by a slower outflow of the permeating component across the vesicle membrane. This dynamics may be exploited advantageously by cells to separate and connect metabolic and signaling routes within their nucleoplasm or cytoplasm depending on external conditions.

Small molecule-mediated self-assembly behaviors of Pluronic block copolymers in aqueous solution: impact of hydrogen bonding on the morphological transition of Pluronic micelles

The influence of hydrogen bonding on the self-assembly behaviors of Pluronic P123 micelles is experimentally and theoretically investigated by introducing three small molecules, i.e. propyl benzoate (PB), propyl paraben (PP) and propyl gallate (PG) into the aqueous solution. It is discovered that the number of phenolic hydroxyl groups and concentration of the tested small molecules exhibit a profound impact on the micellar morphology. Although all the small molecules increase the size and polydispersity of Pluronic micelles in a concentration-dependent manner, the micellar morphologies induced by them vary considerably as demonstrated by DLS and cryo-TEM measurement. PB, without phenolic hydroxyl, cannot bring about the morphological change of P123 micelles, while PP induces a series of morphological transitions from spheres to long worm-like micelles and then to unilamellar vesicles by increasing the PP content. Upon increasing the number of phenolic hydroxyls in small molecules, i.e. PG, the fusion of the intermicellar core takes place, resulting in the formation of large micelles and micellar clusters. A qualitative study by NMR reveals that the different locations of small molecules within the micelles are attributed to the balance of hydrogen bonding and hydrophobic interaction between small molecules and copolymers. In addition, molecular dynamics simulations (MDS) are performed to further confirm the experimental results and provide quantitative information on intermolecular interaction strength. It is supposed that the mechanism of micellar morphological transition mediated by small molecules is ascribed to the hydrogen bonding interactions with varying strengths between the PEO blocks and their phenolic hydroxyls, which governs their locations in micelles, affecting the free energies from different regions of micelles, and consequently leads to the varying micellar morphologies. This study deepens our understanding of the role of hydrgen bonding in the self-assembly behaviors of Pluronic micelles and provides an alternative strategy for manipulating the nanostructure of Pluronic micelles.

Vesicle to micelle transition in the ternary mixture of L121/SDS/D2O: NMR, EPR and SANS studies

Proposed model depicting vesicle to mixed micelle transformation in a ternary mixture of L121/SDS/D₂O.

A simple method for the synthesis of porous polymeric vesicles and their application as MR contrast agents

Because of their low membrane permeability the use of polymeric vesicles in certain drug delivery and molecular imaging applications and as bioreactors is less than ideal. Here, we report a simple method to prepare porous polymeric vesicles that possess high membrane permeability. Specifically, porous vesicles were produced from the aqueous assembly of the diblock copolymer PEG-PBD, and the triblock copolymer PEG-PPO-PEG. It was found that PEG-PPO-PEG-doped polymersomes exhibited improved membrane permeability to molecules less than 5 kDa. Further, these porous vesicles retained molecules ≥10 kDa within their aqueous interiors with no significant leakage. To demonstrate its application, highly efficient magnetic resonance contrast agents were produced from porous polymersomes by encapsulating macromolecules labeled with gadolinium. Due to a fast water exchange rate with surrounding bulk water, these paramagnetic porous polymersomes exhibited higher r₁ relaxivity compared with Gd-encapsulated vesicles with no pores. Due to their simplicity, the porous polymersomes prepared with this method are expected to have additional useful applications.

Continuously manufactured magnetic polymersomes--a versatile tool (not only) for targeted cancer therapy

Micromixer technology was used to prepare polymeric vesicles (Pluronic® L-121) dual loaded with the anti-cancer drug camptothecin and magnetic nanoparticles. Successful incorporation of the magnetic nanoparticles was confirmed by transmission electron microscopy. Dynamic light scattering measurements showed a relatively narrow size distribution of the hybrid polymersomes. Camptothecin polymersomes reduced the cell viability of prostate cancer cells (PC-3) measured after 72 h significantly, while drug-free polymersomes showed no cytotoxic effects. Covalent attachment of a cancer targeting peptide (bombesin) as well as a fluorescent label (Alexa Fluor® 647) to the hybrid polymersomes was performed and specific cell binding and internalization were shown by flow cytometry and confocal microscopy. Relaxometry measurements clearly demonstrated the capacity of magnetic polymersomes to generate significant T2-weighted MRI contrast and potentially allow for direct monitoring of the biodistribution of the polymersomes. Micromixer technology as an easy, fast and efficient way to manufacture hybrid polymersomes as theranostic drug delivery devices is a further step from basic research to personalized medicine.

Nanoparticles with a bicontinuous cubic internal structure formed by cationic and non-ionic surfactants and an anionic polyelectrolyte

Nanoparticles with an internal structure have been prepared by dispersing under dilute conditions poly(acrylic acid) with a polymerization degree n = 6000 (PAA6000) together with a cationic surfactant hexadecyltrimethylammonium hydroxide (C16TAOH) and the non-ionic surfactant penta(ethylene glycol) monododecyl ether (C12E5) in water. The nanoparticles are formed at different mixing ratios in the corresponding two-phase regions (liquid crystalline phase/dilute isotropic phase) of the C16TAPA6000 complex salt/C12E5/water ternary phase diagram. The particles consist of polyacrylate PA6000– polyions, C16TA+ surfactant ions, and C12E5. Their internal ordering was identified by small-angle X-ray scattering (SAXS) to be either bicontinuous cubic with the Ia3d crystallographic space group or normal hexagonal depending upon the amount of C12E5. The bicontinuous cubic phase, to our knowledge never observed before in polyelectrolyte–surfactant particle systems, was inferred by SAXS experiments. The data also showed that this structure is thermoresponsive in a reversible manner. The bicontinuous cubic space group transforms from Ia3d to Im3m as the temperature decreases from 25 to 15 °C. According to dynamic light scattering and electrophoretic mobility measurements, the particles have a well-defined size (apparent hydrodynamic radii RH in the range of 88–140 nm) and carry a positive net charge. The size of the nanoparticles is stable up to 1 month. The faceted nanoparticles are visualized by cryogenic transmission electron microscopy that also reveals their coexistence with thread-like C12E5 micelles.

Rapid ejection of giant Pluronic L121 vesicles from spreading double emulsion droplets

We report the formation of giant Pluronic L121 vesicles with diameters of the order of 200 microm obtained by a previously unreported mechanism that occurs during the solvent evaporation method of vesicle formation. We begin with a water-oil-water double emulsion that is stabilized by dissolving the commercially available triblock copolymer Pluronic L121 in the volatile oil-phase. During the evaporation, the oil phase spreads on the surface of the continuous aqueous phase, leaving behind the aqueous inner droplet of the double emulsion droplet that eventually yields the vesicle. The spreading of the solvent mixture of the oil phase is induced either by the rapid ejection of the inner droplet out of the double emulsion droplet, or by the spreading of the oil phase of a neighboring emulsion droplet.

Polymer-vesicle association

Mixed polymer-surfactant systems have been intensively investigated in the last two decades, with the main focus on surfactant micelles as the surfactant aggregate in interaction. The main types of phase behavior, driving forces and structural/rheological effects at stake are now fairly well understood. Polymer-vesicle systems, on the other hand, have received comparatively less attention from a physico-chemical perspective. In this review, our main goal has been to bridge this gap, taking a broad approach to cover a field that is in clear expansion, in view of its multiple implications for colloid and biological sciences and in applied areas. We start by a general background on amphiphile self-assembly and phase separation phenomena in mixed polymer-surfactant solutions. We then address vesicle formation, properties and stability not only in classic lipids, but also in various other surfactant systems, among which catanionic vesicles are highlighted. Traditionally, lipid and surfactant vesicles have been studied separately, with little cross-information and comparison, giving duplication of physico-chemical interpretations. This situation has changed in more recent times. We then proceed to cover more in-depth the work done on different aspects of the associative behavior between vesicles (of different composition and type of stability) and different types of polymers, including polysaccharides, proteins and DNA. Thus, phase behavior features, effects of vesicle structure and stability, and the forces/mechanisms of vesicle-macromolecule interaction are addressed. Such association may generate gels with interesting rheological properties and high potential for applications. Finally, special focus is also given to DNA, a high charge polymer, and its interactions with surfactants, and vesicles, in particular, in the context of gene transfection studies.

A fluorescence-based technique to construct size distributions from single-object measurements: application to the extrusion of lipid vesicles

We report a novel approach to quantitatively determine complete size distributions of surface-bound objects using fluorescence microscopy. We measure the integrated intensity of single particles and relate it to their size by taking into account the object geometry and the illumination profile of the microscope, here a confocal laser scanning microscope. Polydisperse (as well as monodisperse) size distributions containing objects both below and above the optical resolution of the microscope are recorded and analyzed. The data is collected online within minutes, which allows the user to correlate the size of an object with the response from any given fluorescence-based biochemical assay. We measured the mean diameter of extruded fluorescently labeled lipid vesicles using the proposed method, dynamic light scattering, and cryogenic transmission electron microscopy. The three techniques were in excellent agreement, measuring the same values within 7-9%. Furthermore we demonstrated here, for the first time that we know of, the ability to determine the full size distribution of polydisperse samples of nonextruded lipid vesicles. Knowledge of the vesicle size distribution before and after extrusion allowed us to propose an empirical model to account for the effect of extrusion on the complete size distribution of vesicle samples.

Self-assembly process of different poly(oxystyrene)-poly(oxyethylene) block copolymers: spontaneous formation of vesicular structures and elongated micelles

In the present work, we investigated the micellization, gelation, and structure of the aggregates of three poly(ethylene oxide)-polystyrene oxide block copolymers (E12S10, E10S10E10, and E137S18E137, where E denotes ethylene oxide and S styrene oxide and the subscripts the block length) in solution. Two of them have similar block lengths but different structures (E12S10 and E10S10E10) and the other has longer blocks (E137S18E137). For the first time, the spontaneous formation of vesicles by a poly(oxystyrene)-poly(oxyethylene) block copolymer is reported. These vesicular structures are present when copolymer E12S10 self-assembles in aqueous solution in coexistence with spherical micelles, as confirmed by the size distribution obtained by dynamic light scattering and pictures obtained by polarized optical microscopy, and transmission and cryo-scanning electron microscopies. Vesicle sizes vary between 60 and 500 nm. On the other hand, for copolymers E10S10E10 and E137S18E137, only one species is found in solution, which is assigned to elongated and spherical micelles, respectively. If we compare the high aggregation number derived by static light scattering for the triblock block copolymer micelles, with the maximum theoretical micellar dimensions compatible with a spherical geometry, we can see that the micellar geometry cannot be spherical but must be elongated. This is corroborated by transmission electron microscopy images. On the other hand, tube inversion was used to define the mobile-immobile (soft-hard gel) phase boundaries. To refine the phase diagram and observe the existence of additional phases, rheological measurements of copolymer E137S18E137 were done. The results are in good agreement with previous values published for other polystyrene oxide-poly(ethylene oxide) block copolymers. In contrast, copolymers E12S10 and E10S10E10 did not gel in the concentration range analyzed. Thus, only certain concentrations of copolymer E10S10E10 were analyzed by rheometry, for which an upturn in the low-frequency range of the stress moduli was observed, denoting an evidence of an emerging slow process, which we assign to the first stages of formation of an elastic network.

Gentle immobilization of nonionic polymersomes on solid substrates

Vesicles from Pluronic L121 (PEO5-PPO68-PEO5) triblock copolymers were first stabilized by a permanent interpenetrating polymer network and then gently immobilized onto a glass or mica surface. Fluorescence-labeled micrometer-sized vesicles were visualized with confocal laser scanning microscopy, and smaller sized capsules, around 100 nm, were probed by liquid atomic force microscopy. The immobilized vesicles were weakly attached to a negatively charged surface via negatively charged polyelectrolytes in combination with Mg2+ ions and can be reversibly detached from the surface by slightly elevated temperatures. To illustrate that the immobilized vesicles remain responsive to external stimuli, we show that it is possible to transform their shape from spherical to cylindrical by introducing a second Pluronic, namely, P123 (PEO20-PPO70-PEO20). The detailed transition process has been recorded in real time by confocal laser scanning microscopy. Electron microscopy studies confirmed that a similar morphology change also occurs in the bulk.

Rheological study of the shape transition of block copolymer-nonionic surfactant mixed micelles

A rheological study of mixed micelles formed by PEO-PPO-PEO triblock copolymer P123 and nonionic surfactant C12EO6 in aqueous solutions has been carried out with the purpose of investigating the time dependence of a shape transition of the mixed micelles and characterizing the shape before and after the transition. The rheology results presented in this report give clear evidence that the P123-C12EO6 mixed micelle grows and changes gradually in shape from spherical to elongated (rodlike) geometry with increasing temperature. These results are in accordance with the results found in the parallel dynamic and static light scattering and calorimetrical investigation.1,2 By using steady-state rheology, the time dependence of the sphere-to-rod transition of the mixed micelle system was carefully followed with time and temperature as simultaneously recorded variables in the experiments. This was performed by a designed novel experimental procedure. A temperature ramp was applied at a rate of 2.6 degrees C/min from a temperature below to a temperature above the shape transition at a constant shear rate while the viscosity of the solution was measured. The investigation was limited to two different compositions, surfactant-to-copolymer molar ratios (MR=nC12EO6/nP123) of 2.2 and 6.0 with varying total concentration from 1.5 to 21 wt % in comparison with the neat component. At low concentration, a slow transition was observed, which indicated that the mixed micelles are still growing into rods for several minutes after reaching the final temperature. At a total concentration of 4.0 wt % and above, the system reached equilibrium quickly. A concentration-dependent kinetic process is therefore anticipated, which was also found in the time-resolved static light scattering experiments previously performed (Löf, D.; Schillén, K.; Olofsson, G.; Niemiec, A.; Loh, W. J. Phys. Chem. B 2007, 111, 5911). At concentrations above 10 wt %, shear-thinning behavior was observed for the mixed solutions, which strongly suggests the extended shape of the mixed micelles after the shape transition. The obtained zero-shear viscosity at the investigated molar ratios was found to be lower with higher molar ratios, which indicates that the mixed micelles both in the spherical and in the rodlike state becomes smaller with higher content of C12EO6. These results correlate well with the obtained results from the previous dynamic light scattering measurements on the same system (Löf, D.; Schillén, K.; Olofsson, G.; Niemiec, A.; Loh, W. J. Phys. Chem. B 2007, 111, 5911).

Aggregation behavior of polypropylene oxide end-capped by positive charges

We investigated the aggregation behavior of poly(propylene oxide) with positive charges at both ends in aqueous solution by means of solution turbidity, dynamic light-scattering, solubilization of fluorescence probe, and optical microscopic observation. The positive charges were produced by protonation of terminal NH2 groups attached to the polymer composed of 33 PO units. It was found that the polymer exists as unimers at low temperature and as micelles at high temperature, whereas at intermediate temperature, there appear different aggregation states depending on the polymer concentration; i.e., 100-nm size aggregates which might be vesicles, 1-microm size particles (oil droplets), and a certain turbid phase showing a characteristic texture under optical microscopic observation. Filtration experiments to remove the oil droplets showed that the insoluble components with less hydrophilic property included in the polymer sample are responsible for the formation of oil droplets. Comparison of the phase diagrams obtained for the polymer/H2O mixtures before and after the filtration treatment suggests that the formation of 100 nm size aggregates and some unidentified phase in between unimer and micellar regions is an intrinsic property of the poly(propyrene oxide) chain end-capped by electrical charges.

Biocompatible polymer vesicles from biamphiphilic triblock copolymers and their interaction with bovine serum albumin

The self-assembly of the biamphiphilic triblock copolymer poly(ethylene oxide)-b-poly(caprolactone)-b-poly(acrylic acid) into polymer vesicles is studied. The vesicles provide both biocompatibility and biodegradability. Moreover, the biamphiphilic nature of the triblock copolymer provides different surface properties in the interior and in the outer interface of the vesicles. Preparation of the aggregates by direct dissolution of the copolymer in a solution of albumin does not alter the morphology of the aggregates, and thus, they have the potential to immobilize protein molecules. Since a part of the protein is encapsulated in the interior of the vesicles, they can be used as nanocontainers. A further fraction of the protein is bound to the outer interface, which is primarily composed of the poly(acrylic acid) tails. Immobilization of protein on the outer interface can stabilize the colloidal particles and also provide them with a biofunctional component.

Aggregation behavior of polypropylene oxide with electric charges at both ends in aqueous solution

The aggregation behavior of polypropylene oxide (PPO) with positive charges at both ends was investigated in aqueous solution by means of the measurements of solution turbidity, dynamic light-scattering, differential scanning calorimetry, and dye solubilization. The positive charges were produced by protonation of terminal NH(2) groups attached to the polymer composed of 33 PO units. It was found that the aggregation behavior is quite sensitive to temperature. At low temperature, the polymer dissolves in water as a unimer. When temperature is increased, the unimer solution undergoes a phase separation to give a turbid solution. Further increase in temperature produces a transparent micellar solution. The aggregation of the polymer molecules must be induced by the dehydration of PPO chain caused by temperature increase. According to the analysis of heat absorptions associated with the melting of the solid mixture and the phase separation of the unimer solution, it is suggested that approximately 10% dehydration of PPO chain causes the phase separation. The temperature-composition phase diagram of aqueous mixture of this polymer was constructed on the basis of turbidity and DSC experiments, which reveals the aggregation behavior of this polymer in aqueous medium as a function of concentration and temperature.

Double Electron Electron Resonance as a Method for Characterization of Micelles

Double electron electron resonance (DEER) is an experimental technique used to determine distance between electron spins. In this work, we show that it can be used to study the properties of micelles in solution, specifically their volume and the aggregation number. The feasibility of the method is tested on micelles of Pluronic block copolymers, PEO(x)-PPO(y)-PEO(x), built from chains of poly(ethylene oxide) (PEO), comprising the more hydrophilic corona, and a poly(propylene oxide) (PPO) block constituting the hydrophobic core. In this work, the dimensions of the hydrophobic core of micelles of Pluronic L64 (x = 13, y = 30), P123 (x = 20, y = 70), and F127 (x = 106, y = 70) and their aggregation number were studied. This was done using the spin-probe 4-hydroxy-tempo-benzoate (4HTB), which is hydrophobic and is localized in the hydrophobic core of the micelles and does not dissolve in aqueous solution. The measurements were carried out on frozen solutions, freeze quenched after equilibration at 50 degrees C. It was found that the hydrophobic core radii occupied by 4HTB in 7.5 wt % F127 and 6 wt % L64 are 4.0 +/- 0.05 and 3.8 +/- 0.1 nm, respectively, and the corresponding aggregation numbers are 57 +/- 2 and 206 +/- 14. The micelles of 6 wt % P123 were found to have a rod shape, and the addition of 4HTB at concentrations higher than 0.7 mM resulted in a phase transitioned to spherical micelles. Finally, this study also showed that the micelle structure is preserved upon rapid freezing.

Formation of internally nanostructured triblock copolymer particles

Particles with an internal structure have been found in dilute water solutions of a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), which has short hydrophilic PEO endblocks compared to the central hydrophobic PPO block (EO5PO68EO5, L121). The properties of the block copolymer particles (i.e., their structure, size, and time stability) have been investigated using cryogenic transmission electron microscopy (cryo-TEM) in combination with dynamic light scattering (DLS) and turbidity measurements. The particles were formed in dilute solutions by quenching the temperature to temperatures where the reversed hexagonal phase is in equilibrium with a solution of unaggregated L121 copolymers (L1). From the DLS measurements, a mean hydrodynamic radius of 158 nm was extracted. The time-scan turbidity measurements were found to be unchanged for about 46 h. At higher copolymer concentrations, a reversed hexagonal phase (H2) exists in the L121/water system. SAXS was used to investigate the internal structure of the dispersed L121-based particles containing 15 wt % L121. It was found that the internal structure transforms from H2 to an inverse micellar system (L2) as the temperature increases from 37 to 70 degrees C.

Aggregate Morphologies of Amphiphilic ABC Triblock Copolymer in Dilute Solution Using Self-Consistent Field Theory

The complex microstructures of amphiphilic ABC linear triblock copolymers in which one of the end blocks is relatively short and hydrophilic, and the other two blocks B and C are hydrophobic in a dilute solution, have been investigated by the real-space implementation of self-consistent field theory (SCFT) in two dimensions (2D). In contrast to diblock copolymers in solution, the aggregation of triblock copolymers are more complicated due to the presence of the second hydrophobic blocks and, hence, big ranges of parameter space controlling the morphology. By tailoring the hydrophobic degree and its difference between the blocks B and C, the various shapes of vesicles, circlelike and linelike micelles possibly corresponding to spherelike, and rodlike micelles in 3D, and especially, peanutlike micelles not found in diblock copolymers are observed. The transition from vesicles to circlelike micelles occurs with increasing the hydrophobicity of the blocks B and C, while the transition from circlelike micelles to linelike micelles or from the mixture of micelles and vesicles to the long linelike micelles takes place when the repulsive interaction of the end hydrophobic block C is stronger than that of the middle hydrophobic block B. Furthermore, it is favorable for dispersion of the block copolymer in the solvent into aggregates when the repulsion of the solvent to the end hydrophobic block is larger than that of the solvent to the middle hydrophobic block. Especially when the bulk block copolymers are in a weak segregation regime, the competition between the microphase separation and macrophase separation exists and the large compound micelle-like aggregates are found due to the macrophase separation with increasing the hydrophobic degree of blocks B and C, which is absent in diblock copolymer solution. The simulation results successfully reproduce the existing experimental ones.

Vesicle Array-Templated Large-Area Silica Surface Patterns

Micropatterning has important applications in a wide range of areas, including microelectronics, optics, information displays, and biotechnology. Herein, we describe a vesicle-array templating approach for the generation of surface patterns of micrometer-sized silica features on the surfaces of silica monoliths. The approach makes use of tetraethyl orthosilicate as silica precursor, a poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer, EO2PO16EO2, as surfactants, and water, ethanol, and dimethylformamide as solvents. The morphological shapes of produced silica features are synthetically controlled through varying the sequence of silica precursor hydrolysis, vesicle formation, and silica condensation. Prehydrolysis of the silica precursor, before being mixed with the copolymer, gives hollow convex protrusions. Direct mixing of the silica precursor and the copolymer produces concave depressions. An increase in the amount of water in the mixture solution without prehydrolysis of the silica precursor results in hierarchical patterns of larger concave depressions attached with smaller convex protrusions. It has further been demonstrated that concave surface patterns can function as microlens arrays that are capable of producing numerous optical images from a common object.

Vesicle Formation from Temperature Jumps in a Nonionic Surfactant System

When heating a dilute sample of the binary system of tetraethyleneglycol dodecyl ether (C12E4) and water from the micellar phase (L1) into the two-phase region of a lamellar phase (L(alpha)), and excess water (W) vesicles are formed. During heating, one passes a region of phase separation in the micellar phase (L1' + L1'') where the initial micelles rapidly fuse into larger aggregates forming the concentrated L1 phase (L1'') with a structure of branched cylindrical micelles, a so-called "living network". The static correlation length of the micelles are increasing with increasing concentration, from ca. 10 nm to 80 nm in the concentration range of 0.0001 g/cm3-0.0035 g/cm3. The overlap concentration was determined to 0.0035 g/cm3. When the temperature reaches the L1' + L(alpha) region the network particles transform into bilayer vesicles with a z-average apparent hydrodynamic radius in the order of 200 nm depending on the composition. The size of the final vesicles depends on the extent of aggregation/fusion in the L1' + L1'' region and hence on the rate of heating. The aggregation/fusion in the L1' + L1'' is slower than diffusion-limited aggregation, and it is shown that 1/100 of the collisions are sticky results in the fusion event.