Growth Of Micelles Research Articles

Coarse-grained molecular dynamics study on the rheological behaviors of surfactant aqueous solution

The rheological behavior in a binary system of cetyltrimethylammonium chloride (CTAC) and counter ion salts aqueous solution was studied using MARTINI force field coarse-grained molecular dynamics (CGMD) simulations. The results show that the shear viscosity of the surfactant aqueous solution has a plateau at low shear rates and a shear-thinning regime at high shear rates, which are consistent with the published data. Meanwhile, the shear viscosity increases with increasing the concentration ratio (R) of the counter ion salt to CTAC surfactant, but when R > 1.0, the shear viscosity increases slowly and it appears to reach a plateau. This simulation result agrees with Sureshkumar's report that the mechanical properties of a surfactant-counter ion salt micelle will be stable when CTA+ ions carry the maximum number of Sal− ions (R = 1.0). Then the correlation between the shear viscosity and the micellar structure was analyzed by investigating the micelle morphology and the final largest micelle size under various shear flows. It shows that the network, branched, and wormlike micelles formed by low shear rate, no shear rate, and high shear rate, respectively. The network structure corresponds to the highest shear viscosity and the wormlike resulting in the lowest viscosity. Furthermore, the simulation suggests that increasing temperature and/or shear rate can promote the micelle growth in surfactant aqueous solution. At last, we simulated the effect of counter ion salts on the micelle formation and found that the final largest micelle of CTAC/NamSal binary system is bigger than that of CTAC/NaSal followed by CTAC/NaCl, which agrees with the published experiments.

Viscosity Peak due to Shape Transition from Wormlike to Disklike Micelles: Effect of Dodecanoic Acid.

Here, we have investigated the synergistic growth of long wormlike micelles and their transformation into disklike micelles, which occurs in three-component solutions composed of sodium lauryl ether sulfate (SLES; anionic), cocamidopropyl betaine (CAPB; zwitterionic), and dodecanoic acid (HC12; nonionic). The solution rheology is characterized in terms of zero-shear viscosities and characteristic times for micellar breaking and reptation. Furthermore, the microstructure evolution, leading to the observed rheological behavior, is revealed by cryo-transmission electron microscopy (TEM) micrographs. In all cases, the CAPB-to-SLES ratio is fixed, whereas the fatty acid concentration is varied. At a certain HC12 concentration, the solution viscosity passes through a maximum. The cryo-TEM imaging indicates that wormlike micelles appear before the peak, grow further up to the peak, and finally transform into disklike aggregates (a very rare micellar structure) after the peak. The transformation of worms into disks leads to a drop in viscosity because the length-to-thickness aspect ratio of the disks is significantly lower than that of the worms. In this article, we elucidate the structure-rheology relations in micellar solutions that might be applied for the design of personal-care and household formulations.

Growth of wormlike micelles of surfactant induced by embedded polymer: role of polymer chain length.

Incorporation of polymer chains into wormlike surfactant micelles, which find a large range of applications, offers the opportunity to modify their structure and properties. In this paper, using spectroscopic, scattering and rheological techniques and computer simulations, we study the incorporation of poly(4-vinylpyridine) of two different molecular weights (MWs) into entangled networks of wormlike surfactant micelles of potassium oleate. Using NMR-spectroscopy we show that, independent of its MW, the polymer incorporates into the core-corona interface of the surfactant micelles. According to SANS data, the polymer does not alter the micelle structure or the micelle radius, but diminishes the packing density of the surfactant. At the same time, rheology reveals a stark difference between the surfactant networks with embedded polymers of different MWs. Networks with the higher-MW polymer possess larger viscosity and a longer relaxation time, which we attribute to the larger length of the hybrid micelles. Moreover, we demonstrate that in an intermediate concentration range the higher-MW polymer is able to link neighbouring surfactant micelles together, which has never been previously observed. However, with a further increase in polymer content the micelles become smaller due to the high breaking susceptibility of the boundaries of polymer-containing sections, leading to the stabilization of micellar end-caps by the embedded macromolecules. This process is more prominent in the case of the shorter polymer. Our finding that an increased MW of macromolecules permits the formation of longer hybrid micelles and enhances their rheological properties is of obvious importance for the fundamental understanding of polymer-surfactant interactions and the development of new industrial formulations based on hybrid polymer-wormlike surfactant micelles.

Polymer Self-Assembly into Unique Fractal Nanostructures in Solution by a One-Shot Synthetic Procedure.

A fractal nanostructure having a high surface area is potentially useful in sensors, catalysts, functional coatings, and biomedical and electronic applications. Preparation of fractal nanostructures on solid substrates has been reported using various inorganic or organic compounds. However, achieving such a process using polymers in solution has been extremely challenging. Here, we report a simple one-shot preparation of polymer fractal nanostructures in solution via an unprecedented assembly mechanism controlled by polymerization and self-assembly kinetics. This was possible only because one monomer was significantly more reactive than the other, thereby easily forming a diblock copolymer microstructure. Then, the second insoluble block containing poly(p-phenylenevinylene) (PPV) without any side chains spontaneously underwent self-assembly during polymerization by an in situ nanoparticlization of conjugated polymers (INCP) method. The formation of fractal structures in solution was confirmed by various imaging techniques such as atomic force microscopy, transmission electron microscopy (TEM), and cryogenic TEM. The diffusion-limited aggregation theory was adopted to explain the branching patterns of the fractal nanostructures according to the changes in polymerization conditions such as the monomer concentration and the presence of additives. Finally, after detailed kinetic analyses, we proposed a plausible mechanism for the formation of unique fractal nanostructures, where the gradual formation and continuous growth of micelles in a chain-growth-like manner were accounted for.

Effects of Calcium Ions on the Solubility and Rheological Behavior of a C22-Tailed Hydroxyl Sulfobetaine Surfactant in Aqueous Solution.

Effects of calcium ions (Ca2+) on the solubility, aggregate structure, and rheological behavior of a C22-tailed zwitterionic surfactant, erucyl dimethyl amidopropyl hydroxyl sulfobetaine (EHSB), have been investigated in aqueous solution. In comparison with sodium ions (Na+), Ca2+ ions exhibit a much higher efficiency in decreasing the Krafft temperature (TK) of EHSB. Specifically, contrary to Na+ ions which have no obvious effect on the rheological properties of the EHSB solution, Ca2+ ions increase the viscosity of the EHSB solution at lower EHSB concentration, and enhance its elasticity at higher EHSB concentration. Moreover, Ca2+ ions raise the temperature needed for the elastic-to-viscous transition of the EHSB solution at higher concentration. At lower EHSB concentration, the hydrophobic interaction between the ultralong hydrocarbon chains induces a tighter packing of the hydrophobic chains by forming a more stretched configuration, while at higher EHSB concentration, the electrostatic attraction between Ca2+ ions and the sulfonate groups of EHSB induces a tighter packing of the headgroups by forming Ca2+-mediated bridges among the EHSB headgroups. Besides, the above interactions may strengthen the hydrogen bonding of OH groups and/or of C═O amide groups, which in turn facilitates the compact packing of the surfactant molecules in aggregates and promotes the growth and entanglement of wormlike micelles. Thus, the EHSB solution shows Ca2+-dependent rheological behaviors. The solubility and rheological properties of the ultralong chain surfactant solution can be simultaneously improved with the addition of divalent Ca2+ ions.

Directly Observing Micelle Fusion and Growth in Solution by Liquid-Cell Transmission Electron Microscopy.

Amphiphilic small molecules and polymers form commonplace nanoscale macromolecular compartments and bilayers, and as such are truly essential components in all cells and in many cellular processes. The nature of these architectures, including their formation, phase changes, and stimuli-response behaviors, is necessary for the most basic functions of life, and over the past half-century, these natural micellar structures have inspired a vast diversity of industrial products, from biomedicines to detergents, lubricants, and coatings. The importance of these materials and their ubiquity have made them the subject of intense investigation regarding their nanoscale dynamics with increasing interest in obtaining sufficient temporal and spatial resolution to directly observe nanoscale processes. However, the vast majority of experimental methods involve either bulk-averaging techniques including light, neutron, and X-ray scattering, or are static in nature including even the most advanced cryogenic transmission electron microscopy techniques. Here, we employ in situ liquid-cell transmission electron microscopy (LCTEM) to directly observe the evolution of individual amphiphilic block copolymer micellar nanoparticles in solution, in real time with nanometer spatial resolution. These observations, made on a proof-of-concept bioconjugate polymer amphiphile, revealed growth and evolution occurring by unimer addition processes and by particle-particle collision-and-fusion events. The experimental approach, combining direct LCTEM observation, quantitative analysis of LCTEM data, and correlated in silico simulations, provides a unique view of solvated soft matter nanoassemblies as they morph and evolve in time and space, enabling us to capture these phenomena in solution.

Micellar Properties and Antimicrobial Activityof a Mixed Surfactant System Constituted by Sodium Dodecyl Sulfate and Cetylpyridinium Chloride

Abstract: Objective: Micellar properties of sodium dodecyl sulfate (NaDS) was examined in the presence of cetylpyridinium chloride (CPC) by means of surface tension, viscosity, dye solubilization, cloud point (CP) measurements.Antimicrobial activities of single and binary systems were also investigated. Results: A decrease in critical micelle concentration (CMC) and increase in solubilizing power for NaDS was observed with increasing CPC concentration. At the highest CPC concentration studied (0.1 M), the surface tension decreased up to 51 mN / m.Also, viscosity results showed growth in NaDS micelles (50 mM) up to the 0.1 M CPC concentration. Antimicrobial activity of NaDS, CPC and NaDS in presence of CPC was investigated against ten different strains of bacteria and ayeast which was not investigated up to now. The susceptibilities of the microorganism were determined by the agar diffusion method. The results showed that NaDS and CPC have a antimicrobial activity but NaDS in presence of CPC has not antimicrobial activity on the bacterial and yeast. Key words: Mixed Micellization, NADS, CPC, Antimicrobial Activity.

Self-Assembly of Lecithin and Bile Salt in the Presence of Inorganic Salt in Water: Mesoscale Computer Simulation.

The influence of inorganic salt on the structure of lecithin/bile salt mixtures in aqueous solution is studied by means of dissipative particle dynamics simulations. We propose a coarse-grained model of phosphatidylcholine and two types of bile salts (sodium cholate and sodium deoxycholate) and also take into account the presence of low molecular weight salt. This model allows us to study the system on rather large time and length scales (up to about ∼20 μs and 50 nm) and to reveal mechanisms of experimentally observed increasing viscosity upon increasing the low molecular weight salt concentration in this system. We show that increasing the low molecular weight salt concentration induces the growth of cylinder-like micelles formed in lecithin/bile salt mixtures in water. These wormlike micelles can entangle into transient networks displaying perceptible viscoelastic properties. Computer simulation results are in good qualitative agreement with experimental observations.

Rheological Properties and Microstructure Transition in Mixture of Zwitterionic Surfactant, Anionic Surfactant and Salts in Sorbitol/H2O Solvent: 2. Effect of Salts and Sorbitol

AbstractThe impact of mixed salts and sorbitol on the viscoelastic properties of a multi‐component system, made of a zwitterionic surfactant cocoamidopropyl betaine (CAPB), an anionic surfactant sodium lauryl sulfate (SLSS) and mixed salts (tetrasodium pyrophosphate, sodium acid pyrophosphate, saccharin and sodium fluoride) in sorbitol/H2O mixed solvent are systematically investigated by steady state and dynamic rheology. As reported previously, the viscosity of the mixed system passes through a maximum with increase in the SLSS mass fraction (XSLSS) at a fixed total surfactant concentration, salt concentration (Csalt) and mass ratio of sorbitol in mixed solvent (R). The shape of the XSLSS‐dependent viscosity curve does not change regardless of Csalt and R, but adding salts or sorbitol has different effects on the rheological properties of this system. The former due to a high screening effect plays an important role in the elongation and entanglement of the wormlike micelles, facilitating the enhancement of rheological properties and the formation of Maxwell fluids. The latter has a dual effect on the rheological properties and phase behavior of the mixtures. A certain amount of sorbitol can promote the formation entangled wormlike micelles, while the effect is reversed if the sorbitol content is too large. The electrostatic and hydrophobic interaction between CAPB and SLSS are the prerequisite for the aggregate formation and transition. Meanwhile, the aggregation behaviors are strongly influenced by the balance between low dielectric constant, strong solvophobic interaction and steric effect of sorbitol with the ability to form hydrogen bonds which favors the growth of micelles, and appearance of aqueous two‐phase systems with smaller amounts of wormlike micelles in CAPB‐rich regions which oppose enhancement of rheological properties. Our findings provide a new insight and approach to control and adjust the phase behavior of such a complicated applied multi‐component system.

Wormlike reverse micelles in lecithin/bile salt/water mixtures in oil

Knowing the ability of water and bile salts to promote the reverse wormlike micelle growth in lecithin/water or lecithin/bile salt mixtures in oil, this work was aimed at elucidating the association properties of the three solutes lecithin, water and the bile salt (BS) sodium deoxycholate in cyclohexane. By systematically changing the fraction of the two additives (i.e.: water and BS) we could identify a region at low additive/lecithin molar ratios where stable wormlike micelle dispersions were formed. Small angle X-ray scattering and oscillatory rheology measurements demonstrated that the ability of bile salt and water to transform the originally spherical lecithin reverse micelles into wormlike micelles and thereby impart to the sample viscoelastic properties is preserved in the three-solute mixture. The results suggest that reverse micelle including both bile salt and water are formed in this system. Reasonably the two primers interact with the same region of the lecithin headgroups and are complementary in altering the packing parameter of the amphiphile to values suitable for the formation of cylindrical aggregates.

Shape transition in ABC triblock copolymer micelles complexed with SDS through quaternized polyvinyl pyridine central block

Polystyrene-b-poly-2-vinylpridine-b-polyethyleneoxide (PS13-PVPy62-PEG47) block copolymer forms spherical core-shell-corona micelles (~50 nm) in water. At acidic pH~3, the central PVPy block gets quaternized (hydrophilic) and gets complexed with sodium dodecyl sulfate (SDS), which strongly interacts with PVPy+ electrostatically as reflected from marked increase in turbidity. The charge neutralization of the central block and accordingly favored hydrophobicity induces interesting structural transitions. Cryo-TEM images for micellar solution of block copolymer in the presence of 10 mM SDS at pH~3 show presence of micelles of ribbon type and threadlike morphology. SANS measurements support the micelle growth and shape transition for the block copolymer aggregates as fitted by core-shell model.

Spontaneous evolution of nanostructures by light‐driven growth of micelles obtained from in situ nanoparticlization of conjugated polymers

ABSTRACTTo simplify processes to produce self‐assembled nanostructures from polymeric materials, there have been several attempts for in situ self‐assembly of block copolymers. As one of these strategies, we developed the in situ nanoparticlization of conjugated polymers (INCP) process to construct various stable nanostructures without postsynthetic treatments. To get spontaneous mesoscopic evolution of the nanostructures obtained by INCP, a new strategy utilizing a unique conformational change of the conjugated polymer is reported herein. The combination of living ring‐opening olefin metathesis polymerization (ROMP) and cyclopolymerization produced block and gradient copolymers through one‐pot or one‐shot polymerization, which initially formed spherical micelles via INCP. Then, the core block of the micelle stiffened through a coil‐to‐rod conformational change by simple aging in organic solvents because of cis‐to‐trans isomerization of the conjugated polymer under light. Subsequently, this enhanced the π‐π interaction among the cores, and eventually promoted the growth of stable nanostructures from spheres to 1D‐nanocaterpillars or 2D‐sheet‐like architectures. This time‐dependent macroscopic evolution provides deeper insight into the production of a variety of kinetically fixed nano‐ and mesoscale structures through INCP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3058–3066

Cavitation-enabled rapid and tunable evolution of high-χN micelles as templates for ordered mesoporous oxides.

The kinetic-entrapment of block copolymer micelles enables size-persistence, however tuning micelle sizes under such conditions remains challenging. Agitation-induced chain exchange via vortexing is limited by the production of solution-air interfaces. Here, we use ultrasonic cavitation for rapid interface production that accelerates micelle growth by an order of magnitude over vortexing.

Impact of Salt Co- and Counterions on Rheological Properties and Structure of Wormlike Micellar Solutions.

Rheological properties of aqueous solutions of long-tailed cationic surfactant erucyl bis-(hydroxyethyl)methylammonium chloride (EHAC) were examined as a function of concentration Cs of different inorganic salts (KCl, CaCl2, and LaCl3) at a fixed surfactant concentration of 0.6 wt %. The structural evolution of micelles was followed by small-angle neutron scattering and cryogenic transmission electron microscopy. It was observed that, upon addition of salt, the zero-shear viscosity η0 of semidilute surfactant solutions goes through a maximum by passing the following three regimes: η0 ∼ Cs10 (regime I), η0 ∼ Cs3.5 (regime II), and η0 ∼ Cs-2 (regime III). In regime I, the micelles grow in length; in regime II, the linear growth of micelles proceeds simultaneously with their branching; and in regime III, the branching becomes dominating. With increase in the salt valence, the viscosity curves shift to a lower salt content, indicating that these salts are more effective in inducing micellar elongation and branching, as they contain a larger amount of anionic species Cl- screening the repulsion between cationic surfactant heads. Diverse roles of salt co- and counterions (i.e., salt ions that are similar and oppositely charged with respect to surfactant head groups) at different salt concentrations were demonstrated. It was shown that at low salt concentrations corresponding to the rising branch of the viscosity curve (regimes I and II), salt counterions (Cl-) fully determine the rheological behavior of the system. At high salt concentrations, when the electrostatic repulsions between micelles and salt co-ions are essentially screened, the co-ions start affecting the rheological properties. Under these conditions, monovalent co-ions (K+) provide much lower viscosity of surfactant solutions than the multivalent ones (Ca2+, La3+), which is consistent with theoretical predictions that suggest the penetration of K+ inside the micellar corona increasing the charge of the micelles and therefore hindering their growth.

Synergistic Growth of Giant Wormlike Micelles in Ternary Mixed Surfactant Solutions: Effect of Octanoic Acid.

The synergistic growth of giant wormlike micelles in ternary mixed solutions composed of an anionic surfactant (sodium laurylethersulfate, SLES), a zwitterionic surfactant (cocamidopropyl betaine, CAPB), and octanoic acid (HC8) is studied. Rheological data and their analysis in terms of Cole-Cole plots and micellar characteristic times are presented, and the micellar structures behind the observed rheological behavior are revealed by cryo-TEM micrographs. The surfactant composition is fixed near the maximal micelle size of the binary SLES + CAPB system, whereas the concentration of HC8 is varied. At a given HC8 concentration, the viscosity of the ternary micellar solutions exhibits a very high and sharp peak. Polarized-light optical microscopy indicates that all investigated solutions are isotropic rather than liquid-crystalline. The cryo-TEM imaging shows complex phase behavior: wormlike micelles to the left of the peak, giant entangled wormlike micelles at the peak, and long wormlike micelles coexisting with multiconnected micellar aggregates to the right of the peak. The formation of multiconnected micelles leads to a drop in viscosity at the higher concentrations. The results contribute to a better understanding of the structure-rheology relations in micellar surfactant solutions and could be useful for controlling the properties of formulations in personal-care and house-hold detergency.

Influence of cleavage of photosensitive group on thermally induced micellization and gelation of a doubly responsive diblock copolymer in aqueous solutions: A SANS study

In the present study, small-angle neutron scattering (SANS) was used to investigate the temperature and concentration dependence of micelle formation and growth of a thermo- and light-responsive hydrophilic block copolymer and the influence of removing photosensitive group. The water-soluble polymer poly(ethylene oxide)- b -poly(ethoxytri(ethylene glycol) acrylate- co - o -nitrobenzyl acrylate) (PEO- b -P(TEGEA- co -NBA) underwent sol-gel/gel-sol transitions in response to temperature changes in the range of 15–55 °C in a 25 wt% aqueous solution. The SANS data showed that individual chains existed at low temperatures and dilute solutions. Spherical micelles formed and packed into an ordered structure at elevated temperatures and high concentrations. Data fitting revealed that the micelle growth followed both micelle fusion and unimer insertion mechanisms after the critical micelle temperature was reached in moderately concentrated solutions whereas the fusion mechanism was dominant at higher temperatures. The UV exposure led to a 22% expansion in chain dimension at the unimer stage due to repulsive interactions between the ionized segments after the removal of the light sensitive group. The higher onset temperature of sol-gel transition after irradiation was mainly ascribed to the higher lower critical solution temperature (LCST). On the other hand, the lower gel-sol transition temperature upon UV exposure was due to the reduction in micelle volume fraction after the cleavage of o -nitrobenzyl group. These results correlated well with the dynamic rheological data. • SANS reveals the molecular mechanisms of polymer micellization and gelation. • The unimers stretch upon the removal of the light sensitive group. • The cleavage of the light sensitive group leads to a narrower gel zone. • The scattering data uncovers material distributions in micelles. • Micelle growth follows both micelle fusion and unimer insertion mechanisms.

Novel interpretations of in vitro polyhydroxyalkanoate polymerization phenomena

Abstract Polyhydroxyalkanoates (PHAs) are gaining popularity as a viable biological alternative to petroleum-derived polyolefin plastic materials, especially because their material properties can be tuned through monomer composition and configuration, an uncommon phenomena in enzymatic polymer products. Because the native function of these polymers is chemical energy storage, the metabolic synthesis routes can vary dramatically from one microorganism to the next, save one crucial enzyme – the PHA synthase, responsible for the direct polymerization and composition of PHAs. For this reason, the field of PHA synthase mechanics is blooming as more variants of this enzyme are discovered. However, due to the complexity associated with this surface-driven micelle growth reaction, the initial reaction conditions dictate a variety of observed behaviors during in vitro kinetic analysis. In this work, we discuss the importance of these initial conditions and their associated behaviors and propose minimal kinetic models to help elucidate the significant mechanics of this complex in vitro reaction. The theory and inferences of this work provide a more complete understanding of in vitro PHA synthesis and aid in the design of future in vitro PHA synthase enzymatic assays.

Generation of a Chiral Giant Micelle.

Over the past few years, chiral supramolecular assemblies have been successfully used for recognition, sensing and enantioselective transformations. Several approaches are available to control chirality of discrete assemblies (e.g., cages and capsules), but few are efficient in assuring chirality for micellar aggregates. Optically active amino acid-derived surfactants are commonly used to generate chiral spherical micelles. To circumvent this limitation, we benefited from the uniaxial growth of spherical micelles into long cylindrical micelles usually called wormlike or giant micelles, upon the addition of cosolutes. This paper describes the unprecedented formation of chiral giant micelles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) upon increasing addition of enantiopure sodium salt of 1,1'-bi-2-naphthol (Na-binaphtholate) as a cosolute. Depending on the concentrations of CTAB and Na-binaphtholate, chiral gel-like systems are obtained. The transition from spherical to giant micellar structures was probed using rheology, cryo-transmission electron microscopy, polarimetry, and electronic circular dichroism (CD). CD can be effectively used to monitor the incorporation of Na-binaphtholate into the micelle palisade as well as to determine its transition to giant micellar structures. Our approach expands the scope for chirality induction in micellar aggregates bringing the possibility to generate "smart" chiral systems and an alternative asymmetric chiral environment to perform enantioselective transformations.

Critical Behavior and Ensuing Phase Separations in Paraben‐Solubilized Micellar Solutions of Ionic Surfactants

AbstractAqueous solutions of cetyltrimethylammonium bromide (CTAB) show micellar growth in the presence of various organic and inorganic additives. The simultaneous presence of some of these additives exhibit synergistic effects on micellar growth in this system due to their diverse nature of influences on the critical packing parameter of CTAB micelles. In this manuscript, we report dynamic light scattering, small‐angle neutron scattering and rheological studies on influences of the widely used preservative butyl paraben and NaCl on the growth and interaction of CTAB micelles. These additives show synergism in micellar growth and induce micellar attraction‐driven phase separations of both upper consolute temperature and lower consolute temperature regimes in aqueous solutions of CTAB. Quite interestingly, such micellar attraction‐driven phase separations are also induced in aqueous systems of other cationic and anionic surfactants in the simultaneous presence of a hydrophobic substance and NaCl. These systematic observations of micellar attraction‐driven phase separation are the first of this kind in aqueous systems of ionic surfactants. The results also suggest that the use of parabens as preservatives in some ionic surfactantbased formulations can also help in tuning their rheological characteristics.

PFS-b-PNIPAM: A First Step toward Polymeric Nanofibrillar Hydrogels Based on Uniform Fiber-Like Micelles

Amphiphilic crystalline-coil diblock copolymers polyferrocenyldimethylsilane-block-poly(N-isopropylacrylamide) of two different block ratios (PFS56-b-PNIPAM190 and PFS26-b-PNIPAM520) were synthesized by a copper-catalyzed azide–alkyne coupling reaction. They exhibited pronounced differences in self-assembly in alcohol solvents. While PFS56-b-PNIPAM190 formed mixtures of spherical and rod-like micelles in ethanol and 2-propanol, PFS26-b-PNIPAM520 formed long fibers of uniform width in these solvents. We used a seeded growth protocol to grow rod-like PFS26-b-PNIPAM520 micelles of uniform lengths. There were two surprising features of this experiment: First, micelle growth was unusually slow and required a long aging time (40 days) for them to reach their final length. Second, the micelles were characterized by a low number of polymer chains per unit length as determined by multiangle light scattering. This result suggests a loose packing of PFS chains in the micelle core. In an attempt to prepare thermoresp...