Micelles In Aqueous Solution Research Articles

Poly(l-Ornithine)-Based Polymeric Micelles as pH-Responsive Macromolecular Anticancer Agents.

Anticancer peptides and polymers represent an emerging field of tumor treatment and can physically interact with tumor cells to address the problem of multidrug resistance. In the present study, poly(l-ornithine)-b-poly(l-phenylalanine) (PLO-b-PLF) block copolypeptides were prepared and evaluated as macromolecular anticancer agents. Amphiphilic PLO-b-PLF self-assembles into nanosized polymeric micelles in aqueous solution. Cationic PLO-b-PLF micelles interact steadily with the negatively charged surfaces of cancer cells via electrostatic interactions and kill the cancer cells via membrane lysis. To alleviate the cytotoxicity of PLO-b-PLF, 1,2-dicarboxylic-cyclohexene anhydride (DCA) was anchored to the side chains of PLO via an acid-labile β-amide bond to fabricate PLO(DCA)-b-PLF. Anionic PLO(DCA)-b-PLF showed negligible hemolysis and cytotoxicity under neutral physiological conditions but recovered cytotoxicity (anticancer activity) upon charge reversal in the weakly acidic microenvironment of the tumor. PLO-based polypeptides might have potential applications in the emerging field of drug-free tumor treatment.

Preparation of pH-Sensitive Polymeric Nanoparticles for the Targeted Delivery of Doxorubicin with High Drug Capacity

In this study, pH-responsive prodrug nanoparticles PEG-Schiff-doxorubicin (PEG-Schiff-DOX) were designed and synthesised using chemical conjugation method and can self-assembly into spherical micelles in aqueous solution. These nanoparticles show good storage stability which can be stored over one week under normal condition. The acid-liable Schiff linker is stable under neutral pH and cleave under acidic environment, allowing the prodrug micelles to withhold DOX anticancer drug when being delivered in human circulation and disassemble to release drug once enter tumor cell tissue or taken into intracellular endosomal and lysosomal compartments. In addition to the enhanced permeation and retention (EPR) effect possessed by nanoparticle [1], the nanoparticle prodrug PEG-Schiff-DOX possess an advanced drug release behaviour, resulting in higher intracellular drug concentration in cancer cells and prolonged time of action. The superior anticancer effect of these nanoparticles against Hela cells is also investigated with CCK-8 assays, demonstrating the great potential for clinical application of PEG-Schiff-DOX in cancer treatment.

Formation of Size-Controllable Tetragonal Nanoprisms by Crystallization-Directed Ionic Self-Assembly of Anionic Porphyrin and PEO-Containing Triblock Cationic Copolymer.

The creation of anisotropic nanostructures with precise size control is desirable for new properties and functions, but it is challenging for ionic self-assembly (ISA) because of the non-directional electrostatic interactions. Herein, the formation of size-controllable tetragonal nanoprisms is reported via crystallization-directed ionic self-assembly (CDISA) through evaporating a micellar solution on solid substrates. First, ISA is designed with a crystalline polyethylene oxide (PEO) containing cationic polymer poly(2-(2-guanidinoethoxy)ethyl methacrylate)-b-poly(ethyleneoxide)-b-poly(2-(2-guanidinoethoxy)-ethylmethacrylate) (PGn -PEO230 -PGn ) and an anionic 5,10,15,20-Tetrakis(4-sulfonatophenyl) porphyrin (TPPS) to form micelles in aqueous solution. The PG segments binds excessive TPPS with amplenet chargeto form hydrophilic corona, while the PEO segments are unprecedentedly dehydrated and tightly packed into cores. Upon naturally drying the micellar solution on a silicon wafer, PEO crystallizationdirects the micelles to aggregate into square nanoplates, which are further connected to nanoprisms. Length and width of the nanoprisms can be facilely tuned by varying the initial concentration. In this hierarchical process, the aqueous self-assembly is prerequisite and the water evaporation rate is crucial for the formation of nanostructures, which provides multiple factors for morphology regulating. Such precise size-control strategy is highly expected to provide a new vision for the design of advanced materials with size controllable anisotropic nanostructures.

Determining sequential micellization steps of bile salts with multi-CMC modeling

HypothesisBile salts exhibit complex concentration-dependent micellization in aqueous solution, rooted in a long-standing hypothesis of increasing size in bile aggregation that has historically focused on the measurement of only one CMC detected by a given method, without resolving successive stepwise aggregates. Whether bile aggregation is continuous or discrete, at what concentration does the first aggregate form, and how many aggregation steps occur, all remain as open questions. ExperimentsBile salt critical micelle concentrations (CMCs) were investigated with NMR chemical shift titrations and a multi-CMC phase separation modeling approach developed herein. The proposed strategy is to establish a correspondence of the phase separation and mass action models to treat the first CMC; subsequent micellization steps, involving larger micelles, are then treated as phase separation events. FindingsThe NMR data and the proposed multi-CMC model reveal and resolve multiple closely spaced sequential preliminary, primary, and secondary discrete CMCs in dihydroxy and trihydroxy bile salt systems in basic (pH 12) solutions with a single model of one NMR data set. Complex NMR data are closely explained by the model. Four CMCs are established in deoxycholate below 100 mM (298 K, pH 12): 3.8 ± 0.5 mM, 9.1 ± 0.3 mM, 27 ± 2 mM, and 57 ± 4 mM, while three CMCs were observed in multiple bile systems, also under basic conditions. Global fitting leverages the sensitivity of different protons to different aggregation stages. In resolving these closely spaced CMCs, the method also obtains chemical shifts of these spectroscopically inaccessible (aka dark) states of the distinct micelles.

Molecular Insights on Morphology, Composition, and Stability of Mixed Micelles Formed by Ionic Surfactant and Nonionic Block Copolymer in Water Using Coarse-Grained Molecular Dynamics Simulations.

The nanoscale association domains are the ultimate determinants of the macroscopic properties of complex fluids involving amphiphilic polymers and surfactants, and hence, it is foremost important to understand the role of polymer/surfactant concentration on these domains. We have used coarse-grained molecular dynamics simulations to investigate the effect of polymer/surfactant concentration on the morphology of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, i.e., pluronics or poloxamers) block copolymer, and ionic surfactants sodium dodecyl sulfate (SDS), mixed micelles in aqueous solution. The proclivity of the surfactant to form the mixed micelles is also probed using umbrella sampling simulations. In this study, we observed that the core of the pluronic + SDS formed mixed micelles consists of PPO, the alkyl tail of SDS, and some water molecules, whereas the PEO, water, and sulfate headgroups of SDS form a shell, consistent with experimental observations. The micelles are spherical at high-pluronic/low-SDS compositions, ellipsoidal at high-SDS/low-pluronic compositions, and wormlike-cylindrical at high-pluronic/high-SDS compositions. The transitions in micelle morphology are governed by the solvent accessible surface area of mixed aggregates, electrostatic repulsion between SDS-headgroups, and dehydration of PEO and PPO segments. The free energy barrier for SDS escape is much higher in mixed micelles than in pure SDS micelles, indicating a stronger tendency for SDS to form pluronic-SDS mixed micelles.

Synthesis of a temperature sensitive graft carbon dioxide‐based copolymer and its evaluation as a nano drug carrier

AbstractIn this study, a temperature sensitive graft carbon dioxide‐based copolymer, poly (propylene oxide‐co‐carbon dioxide‐co‐allyl glycidyl ether)‐poly (N‐isopropylacrylamide)‐polyethylene glycol monomethyl ether (PPAG‐PNIPAm‐mPEG) was synthesized by “Click Chemistry”. The hydrophobic main chain, PPAG, was prepared by the copolymerization of propylene oxide (PO) and allyl glycidyl ether (AGE). The branch chains include hydrophilic mPEG and temperature sensitive poly (N‐isopropylacrylamide). The structure of the polymer was characterized by 1H NMR and IR spectroscopy. Avermectin (AVE) was loaded into the nanoparticles to form PPAG‐PNIPAm‐mPEG@AVE nanoparticles. PPAG‐PNIPAm‐mPEG could self‐assemble into nano‐sized micelles in aqueous solution. And the size, zeta potential, critical micelle concentration (CMC) of PPAG‐PNIPAm‐mPEG nanoparticles can be altered by changing the lengths of the PNIPAm segments. The loading rate and encapsulation rate of PPAG‐PNIPAm‐mPEG@AVE were 36.98% and 89.98% respectively. The temperature sensitiveness of the nanomaterials was confirmed by DLS. The results show that temperature has a certain effect on the AVE release rate of PPAG‐PNIPAm‐mPEG@AVE in vitro. With the decrease of PNIPAm chain length, the AVE release rate decreases, and the contact angle of PPAG‐PNIPAm‐mPEG@AVE decreases compared with that of water.

Unimolecular Micelles from Randomly Grafted Arborescent Copolymers with Different Core Branching Densities: Encapsulation of Doxorubicin and In Vitro Release Study

A series of amphiphilic arborescent copolymers of generations G1 and G2 with an arborescent poly(γ-benzyl L-glutamate) (PBG) core and poly(ethylene oxide) (PEO) chain segments in the shell, PBG-g-PEO, were synthesized and evaluated as drug delivery nanocarriers. The PBG building blocks were generated by ring-opening polymerization of γ-benzyl L-glutamic acid N-carboxyanhydride (Glu-NCA) initiated with n-hexylamine. Partial or full deprotection of the benzyl ester groups followed by coupling with PBG chains yielded a comb-branched (arborescent polymer generation zero or G0) PBG structure. Additional cycles of deprotection and grafting provided G1 and G2 arborescent polypeptides. Side chains of poly(ethylene oxide) were then randomly grafted onto the arborescent PBG substrates to produce amphiphilic arborescent copolymers. Control over the branching density of G0PBG was investigated by varying the length and the deprotection level of the linear PBG substrates used in their synthesis. Three G0PBG cores with different branching densities, varying from a compact and dense to a loose and more porous structure, were thus synthesized. These amphiphilic copolymers behaved similar to unimolecular micelles in aqueous solutions, with a unimodal number- and volume-weighted size distributions in dynamic light scattering measurements. It was demonstrated that these biocompatible copolymers can encapsulate hydrophobic drugs such as doxorubicin (DOX) within their hydrophobic core with drug loading efficiencies of 42-65%. Sustained and pH-responsive DOX release was observed from the unimolecular micelles, which suggests that they could be useful as drug nanocarriers for cancer therapy.

Monascus Yellow Pigment Production by Coupled Immobilized-Cell Fermentation and Extractive Fermentation in Nonionic Surfactant Micelle Aqueous Solution

Microbial fermentation with immobilized cells possesses many advantages. However, this fermentation mode is restricted to the production of extracellular products. Our previous study demonstrated that the extractive fermentation of Monascus spp. in nonionic surfactant micelle aqueous solution can export Monascus pigments that are supposed to be mainly intracellular products to extracellular culture broth and, in the meantime, extracellularly enhance the production of yellow pigments at a low pH condition; consequently, this makes the continuous production of yellow pigments with immobilized Monascus cells feasible. In this study, immobilized-cell fermentation and extractive fermentation in Triton X-100 micelle aqueous solution were successfully combined to continuously produce Monascus yellow pigments extracellularly. We examined the effects of cell immobilization and Triton X-100 on cell growth, pigment production, and pigment composition. In the repeated-batch extractive fermentation with immobilized cells, the biomass in Ca-alginate gel beads continued to grow and reached 21.2 g/L after seven batches, and dominant yellow pigments were produced extracellularly and stable for each batch. The mean productivity of the extracellular yellow pigments reached up to 22.31 AU410 nm/day within the first four batches (13 days) and 19.7 AU410 nm/day within the first seven batches (25 days). The results also provide a new strategy for producing such intracellular products continuously and extracellularly.

Dynamic Light Scattering Based Microrheology of End-Functionalised Triblock Copolymer Solutions.

Nano-sized particles functionalised with short single-stranded (ss)DNAs can act as detectors of complementary DNA strands. Here we consider tri-block-copolymer-based, self-assembling DNA-coated nanoparticles. The copolymers are chemically linked to the DNA strands via azide (N3) groups. The micelles aggregate when they are linked with complementary ssDNA. The advantage of such block-copolymer-based systems is that they are easy to make. Here we show that DNA functionalisation results in inter-micellar attraction, but that N3-groups that have not reacted with the DNA detector strands also change the phase behaviour of the tri-block polymer solution. We studied the triblock copolymer, Pluronic® F108, which forms spherical micelles in aqueous solutions upon heating. We find that the triblock chains ending with either an N3 or N3-DNA complex show a dramatic change in phase behaviour. In particular, the N3-functionalisation causes the chain ends to cluster below the critical micelle temperature (CMT) of pure F108, forming flower-micelles with the N3-groups at the core, while the PPO groups are exposed to the solvent. Above the CMT, we see an inversion with the PPO chains forming the micellar core, while the N3-groups are now aggregating on the periphery, inducing an attraction between the micelles. Our results demonstrate that, due to the two competing self-assembling mechanisms, the system can form transient hydrogels.

Spiropyran-based polymeric micelles in aqueous solution: light-regulated reversible size alterations and catalytic characteristics

Facile light-regulated reversible size changes of spiropyran-based polymeric micelles were investigated, which would be useful in the fabrication of smart nanoreactors in a controllable manner for dye adsorption, catalysis, etc.

Facially Amphiphilic Skeleton-Derived Antibacterial Cationic Dendrimers.

It is urgent to develop biocompatible and high-efficiency antimicrobial agents since microbial infections have always posed serious challenges to human health. Herein, through the marriage of facially amphiphilic skeletons and cationic dendrimers, high-density positively charged dendrimers D-CA6-N+ (G2) and D-CA2-N+ (G1) were designed and synthesized using the "branch" of facially amphiphilic bile acids, followed by their modification with quaternary ammonium charges. Both dendrimers could self-assemble into nanostructured micelles in aqueous solution. D-CA6-N+ displays potent antibacterial activity against Staphylococcus aureus and Escherichia coli, with minimum inhibitory concentrations (MICs) as low as 7.50 and 7.79 μM, respectively, and has an evidently stronger antibacterial activity than D-CA2-N+. Moreover, D-CA6-N+ can kill S. aureus faster than E. coli. The facial amphiphilicity of the bile acid skeleton facilitates the selective destruction of bacterial membranes and endows dendrimers with negligible hemolysis and cytotoxicity even under a high concentration of 16× MIC. In vivo studies show that D-CA6-N+ is much more effective and safer than penicillin G in treating S. aureus infection and promoting wound healing, which suggests facially amphiphilic skeleton-derived cationic dendrimers can be a promising approach to effectively enhance antibacterial activity and biocompatibility of antibacterial agent, simultaneously.

Hollow and porous TiO2 in PVA matrix nanocomposite green synthesis using ionic liquid micelle for Congo red removal from contaminated water

A new green procedure has been applied to prepare TiO2 nanocomposite in polyvinyl alcohol (PVA) matrix using an aqueous micelle solution of ionic liquid 1-methyl-3-octylimidazolium bromide by determining critical micelle concentration (CMC). The COSMO-SAC model has been used to calculate the activity coefficient of water and understand the water molecules’ behavior in the synthesis mixture. The prepared nanocomposite was porous and layered that has been characterized using FT-IR, XRD, DSC, TGA, SEM, EDX, and elemental mapping. The prepared nanocomposite has been used to remove Congo red dye from contaminated water with the adsorption process. The Langmuir, Freundlich, and Temkin isotherms have been used for modeling equilibrium adsorption of dye removal. Also, the optimized process factors have been evaluated that could achieve 97% dye removal in the following conditions: pH = 12, T = 25 ℃, and t = 45 min using 0.2 g TiO2@PVA (Mesh 100)/L of 10 ppm Congo red aqueous solution. Also, the efficiency of the nanocomposite was 88% after 5 recovery cycles from the optimized condition.

Self-aggregation of 32-substituted bacteriochlorophyll-d analogs in aqueous micelle

As naturally occurring bacteriochlorophyll-[Formula: see text] models, zinc methyl (31R)-bacteriopheophorbides-[Formula: see text] possessing ethyl, vinyl, and ethynyl groups at the 32-position were prepared by chemically modifying chlorophyll-[Formula: see text]. The synthetic molecules self-aggregated in an aqueous Triton X-100 micelle solution similarly as in the major light-harvesting antenna of photosynthetic green bacteria to give supramolecularly ordered large oligomers with red-shifted and broadened visible absorption bands, compared with the monomeric bands. The sequential hydrogenation of the 32-ethynyl to ethyl group via the vinyl group gradually suppressed the chlorosomal self-aggregation ability. The successive elongation of the 31-alkyl chain from a methyl to propyl group via an ethyl group also diminished the [Formula: see text]-aggregation ability. These decreases in the self-aggregation were ascribable to the steric enhancement of the 32-substituents near the 31-hydroxy group requisite for the [Formula: see text]-aggregation.

Preparation of a camptothecin analog FLQY2 self-micelle solid dispersion with improved solubility and bioavailability

Background7-p-trifluoromethylphenyl-FL118 (FLQY2) is a camptothecin analog with excellent antitumor efficacy against various solid tumors. However, its poor solubility and low bioavailability limited the development of the drug. Polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus®), an emerging carrier for preparing solid dispersion (SD), encapsulated FLQY2 to circumvent the above limitations.ResultsIn this project, FLQY2-SD was prepared by solvent evaporation method and self-assembled into micelles in aqueous solutions owing to the amphiphilic nature of Soluplus®. The physicochemical characterizations demonstrated that FLQY2 existed in a homogeneous amorphous form in SD and was rapidly dissolved. The micelles did not affect cytotoxicity or cellular uptake of FLQY2 in vitro, and the oral bioavailability was increased by 12.3-fold compared to the FLQY2 cyclodextrin suspension. The pharmacokinetics of FLQY2-SD showed rapid absorption, accumulation in the intestine, and slow elimination via fecal. Metabolite identification studies showed 14 novel metabolites were identified, including 12 phase I metabolites (M1–M12) and 2 phase II metabolites (M13–M14), of which M2 (oxidation after decarboxylation) and M7 (dioxolane ring cleavage) were the primary metabolites in the positive mode and negative mode, respectively. The tumor growth inhibition rate (TGI, 81.1%) of FLQY2-SD (1.5 mpk, p.o./QW) in tumor-bearing mice after oral administration was higher than that of albumin-bound Paclitaxel (15 mpk, i.v./Q4D) and Irinotecan hydrochloride (100 mpk, i.p./QW).ConclusionsThe successful preparation, pharmacokinetics, and pharmacodynamics studies of FLQY2-SD showed that the solubility and bioavailability of FLQY2 were improved, which facilitated the further druggability development of FLQY2.Graphical

Effect of spacer length on the micellization of cationic trisiloxane surfactants

Siloxane surfactants, hydrophobic (poly)siloxane chain and hydrophilic polar headgroup linking with spacer ((CH2)3 or (CH2)3S(CH2)3), exhibit peculiarly chemical and physical properties. The aggregation behavior and surface properties of siloxane surfactant can be influenced by the hydrophobicity of spacer. Cationic trisiloxane surfactants ([Si3-C3-Min]Br, [Si3-C4-Min]Br, and [Si3-C5-Min]Br) with the same imidazolium group, hydrophobic heptamethyltrisiloxane, and spacer (different number of methylene) were synthesized. The effect of the spacer on micellization in aqueous solution was investigated. Compared with 1-methyl-3- trisiloxaneimidazolium chloride ([Si3Min]Cl), critical micelle concentration (CMC), effectiveness (πCMC), and minimum area occupied by a surfactant molecule (Αmin) values of the investigated surfactants decrease with increase the number of methylene in spacer, while, γCMC value increases as the length of spacer increase. The micellization process was enthalpy driven. The ΔHm0 value becomes more exothermic for [Si3-C5-Min]Br attributed to the increasing hydrophobicity of spacer. The ΔHm0 of [Si3-C3-Min]Br is less exothermic than that of [Si3-C4-Min]Br and [Si3-C5-Min]Br. Spherical aggregates with the range of 20–500 nm were formed in aqueous solution at 2 times CMC.

Facile Construction of a Two-in-One Injectable Micelleplex-Loaded Thermogel System for the Prolonged Delivery of Plasmid DNA

Nanoparticle-hydrogel systems have recently emerged as a class of interesting hybrid materials with immense potential for several biomedical applications. Remarkably, the incorporation of nanoparticles into a hydrogel may yield synergistic benefits lacking in a singular system. However, most synthetic strategies require laborious steps to achieve the system, severely restricting the process of translational research. Herein, a facile strategy to access a two-in-one system comprising two distinct polyurethane (PU)-based micellar systems is demonstrated and applied as a novel sustained gene delivery platform, where the two PUs are synthesized similarly but with slightly different compositions. One PU forms cationic micelles that complex with plasmid DNA (pDNA), which are loaded into a thermogel formed by another PU micellar system for the prolonged release of pDNA micelleplexes. Specifically, a thermogelling multiblock PU copolymer (denoted as EPH) was synthesized via the step-growth polymerization of poly(ethylene glycol), poly(propylene glycol), and poly(3-hydroxybutyrate). By further introducing a cationic extender, 3-(dimethylamino)-1,2-propanediol, into the reaction feed, a series of cationic PUs (denoted as EPHD) with varying compositions were obtained. The EPHDs formed positively charged micelles in aqueous solutions, efficiently condensed pDNA into nano-sized micelleplexes (<200 nm) at optimized w/w ratios, and mediated transient green fluorescence protein expression in HEK293T cells at 48 h post-transfection. On the other hand, aqueous EPH solution (4 wt %) was injectable at 4 °C and rapidly gelled upon heating to 37 °C to form a stable hydrogel depot. EPHD/pDNA micelleplexes were easily loaded into EPH by mixing the solutions at 4 °C, before heating to 37 °C, leading to the resultant hydrogel system. The in vitro release study revealed that while free pDNA loaded in the thermogel was completely released in 2 weeks, the release of EPHD/pDNA micelleplexes was prolonged to at least 28 days, suggesting substantial micelleplex-hydrogel interactions. Intact, bioactive, and noncytotoxic EPHD/pDNA micelleplexes in the release media were proved by gel retardation, in vitro gene transfection, and CCK-8 cytotoxicity assay results, respectively. Collectively, this work presents a simple approach to achieving and optimizing a novel two-in-one nanoparticle-hydrogel system for the prolonged delivery of pDNA and may be promising for long-term gene delivery applications.

Pluronic based injectable smart gels with coumarin functional amphiphilic copolymers

Temperature responsive Pluronic F127 micelles were combined with light-responsive coumarin bearing amphiphilic copolymers to obtain both mechanically strong and injectable gels. For this purpose two monomers, 7-(2-methacryloyloxyethoxy)-4-methylcoumarin (CEMA) and 7-methacryloyloxy-4-methylcoumarin (CMA), were synthesized and further polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Well-defined amphiphilic diblock terpolymers were obtained by using preliminarily synthesized polyethylene glycol (PEG) based macroRAFT agent. The structures of copolymers were confirmed with proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier-transform infrared(FT-IR) spectroscopy and gel permeation chromatography (GPC) analyses. Amphiphilic diblock terpolymers self-assembled into micelles in aqueous solution spontaneously and crosslinking of the micelle cores through the photodimerization of coumarin groups under UV irradiation at 350 nm was examined by UV spectroscopy. Hydrogels were prepared using two different methods, PF127-Mx gels formed using polymer micelle solutions with PF127 solid and PF127-Px gels formed by mixing solid polymers with 20 % F127 solution. Upon characterization of hydrogels via dynamic light scattering (DLS) and transition electron microscope (TEM), rheological properties of the gels were evaluated as a function of temperature, composition, UV exposure time, strain and frequency. Injectability tests of hydrogel systems were performed on a texture analyzer and all the formulations were found in the injectable range. The study reveals that hydrogels based on combination of PF127 and coumarin functional terpolymer amphiphiles hold great potential as injectable biomaterials.

Interaction between Triton X100 and Brij 58 in their binary mixed micelles: Micellization in aqueous solution and aqueous solution of Poloxamer 188 at the range of temperature T = (273.15–323.15) K

The micellization of the binary mixture of surfactants Triton X100 – Brij 58 in an aqueous solution (with and without Poloxamer 188) was investigated using a spectrofluorimetric method with pyrene as a probe molecule. There are synergistic interactions between the micellar building units in the binary mixed micelles Triton X100 – Brij 58, which increase with increasing temperature. The analyzed binary mixed micelles possess molar excess entropy. The molar excess Gibbs free energy is a first-order Margules function from the surfactant (Triton X100 or Brij 58) molar fraction in the binary mixed micelles Triton X100 – Brij 58. Poloxamer 188, in the temperature range T = (273.15–323.15) K, does not form micelles. Poloxamer 188 in an aqueous surfactant solution (0.01 w/w) reduces the thermodynamic stabilization of the binary mixed micelle Triton X100 – Brij 58 concerning the state of the same binary mixed micelle when this polymer is not present in an aqueous solution. In the presence of Poloxamer 188, the thermodynamic destabilization of the binary mixed micelle Triton X100 – Brij 58 increases with increasing temperature.

Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO2 Reduction in Aqueous Media.

A triblock amphiphilic polymer derived from the copolymerization of CO2 and epoxides containing a bipyridine rhenium complex in its backbone is shown to effectively catalyze the visible-light-driven reduction of CO2 to CO. This polymer provides uniformly spherical micelles in aqueous solution, where the metal catalyst is sequestered in the hydrophobic portion of the nanostructured micelle. CO2 to CO reduction occurs in an efficient visible-light-driven process in aqueous media with turnover numbers up to 110 (>99 % selectivity) in the absence of a photosensitizer, which is a 37-fold enhancement over the corresponding molecular rhenium catalyst in organic solvent. Notably, the amphiphilic polycarbonate micelle rhenium catalyst suppresses H2 generation, presumably by preventing deactivation of the active catalytic center by water.

Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO2 Reduction in Aqueous Media

AbstractA triblock amphiphilic polymer derived from the copolymerization of CO2 and epoxides containing a bipyridine rhenium complex in its backbone is shown to effectively catalyze the visible‐light‐driven reduction of CO2 to CO. This polymer provides uniformly spherical micelles in aqueous solution, where the metal catalyst is sequestered in the hydrophobic portion of the nanostructured micelle. CO2 to CO reduction occurs in an efficient visible‐light‐driven process in aqueous media with turnover numbers up to 110 (&gt;99 % selectivity) in the absence of a photosensitizer, which is a 37‐fold enhancement over the corresponding molecular rhenium catalyst in organic solvent. Notably, the amphiphilic polycarbonate micelle rhenium catalyst suppresses H2 generation, presumably by preventing deactivation of the active catalytic center by water.