Formation Of Spherical Micelles Research Articles

Preparation of diblock copolymer nano-assemblies by ultrasonics assisted ethanol-phase polymerization-induced self-assembly

Assemblies are widely used in biomedicine, batteries, functional coatings, Pickering emulsifiers, hydrogels, and luminescent materials. Polymerization-induced self-assembly (PISA) is a method for efficiently preparing particles, mainly initiated thermally. However, thermally initiated PISA usually requires a significant amount of time and energy. Here, we demonstrate the preparation of nano-assemblies with controllable morphologies and size using ultrasound (20 kHz) assisted ethanol-phase RAFT-PISA in three hours. Using poly (N, N-dimethylaminoethyl methacrylate) as the macromolecular reversible addition-fragmentation chain transfer agent (PDMA-CTA) to control the nucleating monomer benzyl methacrylate (BzMA), we obtained nano-assemblies with different morphologies. With the length of hydrophobic PBzMA block growth, the morphologies of the assemblies at 15 wt% solid content changed from spheres to vesicles, and finally to lamellae; the morphologies of the assemblies at 30 wt% changed from spheres micelles to short worms, then vesicles, and finally to large compound vesicles. With the same targeted degree of polymerization, nano-assemblies having a 30 wt% solid content display a more evolved morphology. The input of ultrasonic energy makes the system have higher surface free energy, results the mass fraction interval of solventphilic blocks (fhydrophilic) corresponding to the formation of spherical micelles is expanded from fhydrophilic > 45 % to fhydrophilic > 31 % under ultrasound and the fhydrophilic required to form worms, vesicles, and large composite vesicles decreases in turn. It is worth noting that the fhydrophilic interval of worms prepared by ultrasonics assisted PISA gets larger. Overall, the highly green, externally-regulatable and fast method of ultrasonics assisted PISA can be extended to vastly different diblock copolymers, for a wide range of applications.

Self-assembly mechanism, physicochemical analyses and application performance investigations of branched alkyl glycosides with alcohol ether carboxylic acids of varied epoxide numbers.

Green surfactants, specifically alkyl glycosides and fatty alcohol ether carboxylic acids, are known for their biocompatibility, multiresponsiveness, and versatile applications, garnering significant attention in the realms of green and colloid chemistry. This study systematically investigated the mechanism underlying micelle formation within aqueous solutions comprising alcohol ether carboxylic acids featuring diverse EO group chain quantities (AEC-nH, where n equals 5, 7, and 9) and branched alkyl glycosides (IG). The elucidation of these mechanisms sheds light on their prospective application properties. It was observed that the self-assembly of micelles in these hybrid systems is predominantly influenced by hydrogen bonding, electrostatic interactions, and hydrophobic forces. The spherical-rod morphology of the micelles responds to the varying numbers of EO group chains, with an increased number of EO leading to the formation of rod-like micelles, which exhibit relative instability, while a decreased number of EO results in the formation of spherical micelles with relative stability. Additionally, by means of kinetic analysis, it was determined that the micelle formation process of the three hybrid systems is driven by enthalpy, and a mixed diffusion-kinetics adsorption mechanism is involved in the adsorption process. These findings significantly impact their application properties. This report stands as the first exploration of the synergistic mechanisms and application performance of two types of green surfactants in aqueous solutions, considering the influence of different numbers of EO group chains. Not only does it provide fundamental insights into their properties, but it also offers novel perspectives on the applications of green surface activation.

Structural Behavior of Amphiphilic Triblock Copolymer P104/Water System.

A detailed study of the different structural transitions of the triblock copolymer PEO27-PPO61-PEO27 (P104) in water, in the dilute and semi-dilute regions, is addressed here as a function of temperature and P104 concentration (CP104) by mean of complimentary methods: viscosimetry, densimetry, dynamic light scattering, turbidimetry, polarized microscopy, and rheometry. The hydration profile was calculated through density and sound velocity measurements. It was possible to identify the regions where monomers exist, spherical micelle formation, elongated cylindrical micelles formation, clouding points, and liquid crystalline behavior. We report a partial phase diagram including information for P104 concentrations from 1 × 10-4 to 90 wt.% and temperatures from 20 to 75 °C that will be helpful for further interaction studies with hydrophobic molecules or active principles for drug delivery.

Single-Micelle-Templated Synthesis of Hollow Barium Carbonate Nanoparticle for Drug Delivery

A laboratory-synthesized triblock copolymer poly(ethylene oxide-b-acrylic acid-b-styrene) (PEG-PAA-PS) was used as a template to synthesize hollow BaCO3 nanoparticles (BC-NPs). The triblock copolymer was synthesized using reversible addition-fragmentation chain transfer radical polymerization. The triblock copolymer has a molecular weight of 1.88 × 104 g/mol. Transmission electron microscopy measurements confirm the formation of spherical micelles with a PEG corona, PAA shell, and PS core in an aqueous solution. Furthermore, the dynamic light scattering experiment revealed the electrostatic interaction of Ba2+ ions with an anionic poly(acrylic acid) block of the micelles. The controlled precipitation of BaCO3 around spherical polymeric micelles followed by calcination allows for the synthesis of hollow BC-NPs with cavity diameters of 15 nm and a shell thickness of 5 nm. The encapsulation and release of methotrexate from hollow BC-NPs at pH 7.4 was studied. The cell viability experiments indicate the possibility of BC-NPs maintaining biocompatibility for a prolonged time.

Using the SAFT-γ-Mie to Generate Coarse-Grained Force Fields Useable in Molecular Dynamics Simulations: Describing the Micellar Phases of Polyalkylglycols in Aqueous Solutions

In this work, we showcase the potential of the SAFT-γ-Mie equation of state to obtain, in a top-down approach, coarse-grained molecular models capable of describing micellization phenomena. For this purpose, we selected polyethylene oxide (PEO)/polypropylene oxide (PPO) triblock copolymers in aqueous solutions as a case study. The model was fitted to reproduce the thermophysical properties─liquid densities and vapor pressures─of small PEO/PPO oligomers as well as the activity coefficients or liquid–liquid phase diagrams of their binary mixtures with water. At low concentrations, the MD simulations show the formation of spherical micelles of morphology comparable to experiments, with the characteristic star-shaped or flower-shaped morphology depending on the polymer block sequence. The local structure and molecular conformations were analyzed, showing distinctions between the two types of aggregates. At higher concentrations, depending on the co-polymer sequence, the molecules form larger micelles or coalesce into larger aggregates when signs of phase separation are observed, as expected.

Stimuli‐responsive polypeptoid block copolymers containing o‐nitrobenzyl groups with extremely sharp transition

AbstractBioinspired thermoresponsive polymers have received increasing attention for many applications. Here, we report a series of thermoresponsive polypeptoid block copolymers containing o‐nitrobenzyl groups, that is, poly(ethylene glycol)‐b‐poly[N‐[2‐[N‐(o‐nitrobenzyloxycarbonyl)‐amino]‐ethyl]‐glycine] (PEG‐b‐PN[oNB]G), prepared by ring‐opening polymerization. The polypeptoid block copolymers show reversible lower critical solution temperature (LCST)‐type behavior in water with tunable phase transition properties dependent on the pH values, chemical compositions, and concentrations of the copolymers. The dynamic light scattering results reveal the formation of spherical micelles and temperature‐induced aggregation of PEG‐b‐PN(oNB)G. Notably, the phase transition of the block copolymer solution upon heating appears extremely sharp (∆T < 1°C), superior to bench mark poly(N‐isopropylacrylamide). In addition, we present the removal of photo‐responsive o‐nitrobenzyl groups can result in the increased clouding point and even the loss of phase transition properties, acting as an excellent regulator to tune the LCST behavior. We demonstrate that the hydrogen‐bonding interaction may play a critical part on the LCST behavior. The prepared diblock copolymers show great potential for many applications and its structure–property may shed light on highly designable stimuli‐responsive polymeric materials.

How Temperature Rise Can Induce Phase Separation in Aqueous Biphasic Solutions

Ionic-liquid-based acidic aqueous biphasic solutions (AcABSs) recently offered a breakthrough in the field of metal recycling. The particular mixture of tributyltetradecylphosphonium chloride ([P4,4,4,14]Cl), acid, and water presents the unusual characteristic of a lower solution critical temperature (LCST), leading to phase separation upon a temperature rise of typically a few tens of degrees. We address here the microscopic mechanisms driving the phase separation. Using small-angle neutron scattering, we characterized the spherical micelle formation in a binary ionic liquid/water solution and the micelle aggregation upon the addition of acid due to the screening of electrostatic repulsion. The increase in both the acid concentration and the temperature eventually leads to micelle flocculation and phase separation. This last step is achieved through chloride ion adsorption at the surface of the micelle. This exothermic adsorption compensates for the entropic cost, leading to a counterintuitive behavior, and may be generalized to a number of molecular systems with an LCST.

Dissipative particle dynamics simulation on phase behaviour of reduction-responsive polyprodrug amphiphile

ABSTRACT The self-assembly of polyprodrug amphiphile is broadening impact due to the controlled high drug loading content, among others. Here, dissipative particle dynamics simulation is used to study the phase behaviour of the reduction-responsive polyprodrug amphiphile with an alternating copolymer topology and the drug release from the self-assembled micelles under a stimulus. When the polymerisation degree (PD) of the hydrophobic block is fixed, the PD of the hydrophilic block and the overall PD of the amphiphile need being controlled for the amphiphile to form spherical micelles desired for drug delivery. The micelles do not have core–shell structures. The drug hydrophobicity and its compatibility with the hydrophilic block affects the self-assembly and need being carefully considered for spherical micelle formation. In designing the amphiphile, the incompatibility between the drug and the hydrophilic block needs being considered first, followed by selecting both the PD of the hydrophilic block and overall PD of the amphiphile. In the presence of a chemical stimulus, the drug is released as an individual moiety; while released in an aggregate form when an imaginary physical stimulus is present. This work can guide the design of a stimulus-responsive polyprodrug amphiphile with an alternating copolymer topology for drug delivery.

Preparation and mechanism of pH and temperature stimulus-responsive wormlike micelles

A quaternary ammonium salt surfactant with tertiary amine groups (C16MIMBr) was prepared by the reaction of bromohexadecane with N, N, N, N-tetra methylpropane diamine, and the structure of the product was demonstrated by 1H NMR. A viscoelastic wormlike micellar system was constructed with C16MIMBr as the main agent and potassium bromide as the counterion salt, and the ratio of surfactant to counterion was optimized. It was shown that the viscosity of the system was maximum when the molar ratio of the C16MIMBr-KBr system was 1:4, and the rheological test also indicated that the viscoelasticity was best at 1:4. The pH-stimulated responsiveness and temperature-stimulated responsiveness of the C16MIMBr-KBr system were investigated by rheology and cryo-transmission electron microscopy, and the response mechanism was investigated and analyzed. It is shown that when the system is acidic, the positive charges on both sides of the surfactant lead to strong electrostatic repulsions within and between the surfactant molecules, resulting in a cone-like structure of the surfactant molecules and the formation of spherical micelles with very low viscosity. When the system is deprotonated under alkaline conditions, only one end of the surfactant head group is positively charged, and the inter-and intra-molecular electrostatic repulsive forces are greatly weakened, resulting in the intertwined growth of micelles and the formation of wormlike micelles. The temperature response mechanism analysis of the C16MIMBr-KBr system shows that at low temperature, only a small amount of cation can cross-mix with micelles to form a curved vesicle structure due to the low solubility of the system, resulting in a low viscosity of the system. As the temperature rises to 60 °C, the water solubility of the system is enhanced, and it desorbs from the vesicles into the solution. According to the equation of critical accumulation parameter, the critical accumulation parameter of the system decreases and the transition from vesicles to wormlike micelles occurs, leading to an increase in system viscosity.

Downhill, Ultrafast and Fast Folding Proteins Revised.

Research on the protein folding problem differentiates the protein folding process with respect to the duration of this process. The current structure encoded in sequence dogma seems to be clearly justified, especially in the case of proteins referred to as fast-folding, ultra-fast-folding or downhill. In the present work, an attempt to determine the characteristics of this group of proteins using fuzzy oil drop model is undertaken. According to the fuzzy oil drop model, a protein is a specific micelle composed of bi-polar molecules such as amino acids. Protein folding is regarded as a spherical micelle formation process. The presence of covalent peptide bonds between amino acids eliminates the possibility of free mutual arrangement of neighbors. An example would be the construction of co-micelles composed of more than one type of bipolar molecules. In the case of fast folding proteins, the amino acid sequence represents the optimal bipolarity system to generate a spherical micelle. In order to achieve the native form, it is enough to have an external force field provided by the water environment which directs the folding process towards the generation of a centric hydrophobic core. The influence of the external field can be expressed using the 3D Gaussian function which is a mathematical model of the folding process orientation towards the concentration of hydrophobic residues in the center with polar residues exposed on the surface. The set of proteins under study reveals a hydrophobicity distribution compatible with a 3D Gaussian distribution, taken as representing an idealized micelle-like distribution. The structure of the present hydrophobic core is also discussed in relation to the distribution of hydrophobic residues in a partially unfolded form.

Micellization Behaviour of Linear and Nonlinear Block Copolymers Based on Poly(n-hexyl isocyanate) in Selective Solvents.

Block copolymers have attracted significant scientific and economic interest over the last decades due to their ability to self-assemble into ordered structures both in bulk and in selective solvents. In this work, the self-assembly behaviour of both linear (diblocks, triblocks and pentablocks) and nonlinear (miktoarm stars and a block-graft) copolymers based on poly(n-hexyl isocyanate), PHIC, were studied in selective solvents such as n-heptane and n-dodecane. A variety of experimental techniques, namely static and dynamic light scattering, dilute solution viscometry and atomic force microscopy, were employed to study the micellar structural parameters (e.g., aggregation number, overall micellar size and shape, and core and shell dimensions). The effect of the macromolecular architecture, the molecular weight and the copolymer composition on the self-assembly behaviour was studied. Spherical micelles in equilibrium with clusters were obtained from the block copolymers. Thermally stable, uniform and spherical aggregates were found from the triblock copolymers. The poly(n-hexyl isocyanate)-b-polyisoprene-b-poly(n-hexyl isocyanate),-HIH copolymers tend to adopt closed loop conformation, leading to more elongated cylindrical-type structures upon increasing the concentration. Clustering effects were also reported in the case of the pentablock terpolymers. The topology of the blocks plays an important role, since the poly(n-hexyl isocyanate)-b-polystyrene-b-polyisoprene-b-polystyrene-b-poly(n-hexyl isocyanate), HSISH terpolymer shows intermicellar fusion of spherical micelles, leading to the formation of extended networks. The formation of spherical micelles in equilibrium with clusters was obvious in the case of the miktoarm stars, whereas the block-graft copolymer shows the existence of mainly unimolecular micelles.

PLA–PCL–PEG–PCL–PLA based micelles for improving the ocular permeability of dexamethasone: development, characterization, and in vitro evaluation

The aim of the present research was to investigate the feasibility of developing polylactide–polycaprolactone–polyethylene glycol–polycaprolactone–polylactide (PLA–PCL–PEG–PCL–PLA) based micelles to improve ocular permeability of dexamethasone (DEX). PLA–PCL–PEG–PCL–PLA copolymers were synthesized by a ring-opening polymerization method. DEX was loaded into the developed copolymers. The DEX-loaded micelles were characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS) methods. Cytotoxicity of the micelles obtained was investigated on L929 cell line. Cellular uptake was followed by fluorescence microscopy and flow cytometry analyses. The release behavior of DEX from the micelles as well as the drug release kinetics was studied. Corneal permeability was also evaluated using an ex vivo bovine model. The pentablock copolymers were successfully synthesized. The TEM results verified the formation of spherical micelles, the sizes of which was approximately 65 nm. The micelles exhibited suitable compatibility on L929 cells. The release profile showed an initial burst release phase followed by a sustained release phase, the kinetic of which was close to the Weibull’s distribution model. The micelles showed higher corneal permeability in comparison to a marketed DEX eye drop. Taken together, the results indicated that the PLA–PCL–PEG–PCL–PLA micelles could be appropriate candidates for the ocular delivery of DEX, and probably other hydrophobic drugs.

New Insight into the Hierarchical Microsphere Evolution of Organic Three-Dimensional Layer Double Hydroxide: The Key Role of the Surfactant Template.

Surfactants have proven a suitable template agent for the construction of organic three-dimensional layered double hydroxide (O3D-LDH) due to the excellent self-assembled property and ready operation. Although the morphology and growth of O3D-LDH are affected by various factors (initial surfactant concentration, Mg/Al molar ratio, hydrothermal temperature, urea concentration, hydrothermal time, etc.), little is known about the key role of surfactants in the growth behavior and mechanism. In this study, sodium dodecyl sulfate (SDS) was chosen to identify the behavior of the surfactant on the evolution of O3D-LDH with various factors. The as-grown procedure was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmett-Teller analysis. The results demonstrated that the ideal 3D roselike hierarchical structure was obtained at a Mg/Al/urea molar ratio of 2:1:10 and SDS concentration of 0.1 mol L-1 at 150 °C for 6 h. It is worth noting that SDS showed an extraordinary importance regarding the material growth, as it was intrinsically related to the formation of spherical micelles and functioned as an intercalating anion. Furthermore, a possible growth mechanism was proposed to explain the formation of O3D-LDH. Our finding opens a new insight into the role of SDS in the O3D-LDH fabrication and provides a theoretical foundation for other LDH material construction.

3D Micromachined Polyimide Mixing Devices for in Situ X-ray Imaging of Solution-Based Block Copolymer Phase Transitions.

Advances in modern interface- and material sciences often rely on the understanding of a system's structure-function relationship. Designing reproducible experiments that yield in situ time-resolved structural information at fast time scales is therefore of great interest, e.g., for better understanding the early stages of self-assembly or other phase transitions. However, it can be challenging to accurately control experimental conditions, especially when samples are only available in small amounts, prone to agglomeration, or if X-ray compatibility is required. We address these challenges by presenting a microfluidic chip for triggering dynamics via rapid diffusive mixing for in situ time-resolved X-ray investigations. This polyimide/Kapton-only-based device can be used to study the structural dynamics and phase transitions of a wide range of colloidal and soft matter samples down to millisecond time scales. The novel multiangle laser ablation three-dimensional (3D) microstructuring approach combines, for the first time, the highly desirable characteristics of Kapton (high X-ray stability with low background, organic solvent compatibility) with a 3D flow-focusing geometry that minimizes mixing dispersion and wall agglomeration. As a model system, to demonstrate the performance of these 3D Kapton microfluidic devices, we selected the non-solvent-induced self-assembly of biocompatible and amphiphilic diblock copolymers. We then followed their structural evolution in situ at millisecond time scales using on-the-chip time-resolved small-angle X-ray scattering under continuous-flow conditions. Combined with complementary results from 3D finite-element method computational fluid dynamics simulations, we find that the nonsolvent mixing is mostly complete within a few tens of milliseconds, which triggers initial spherical micelle formation, while structural transitions into micelle lattices and their deswelling only occur on the hundreds of milliseconds to second time scale. These results could have an important implication for the design and formulation of amphiphilic polymer nanoparticles for industrial applications and their use as drug-delivery systems in medicine.

Entrapment of an adenine derivative by a photo-irradiated uracil-functionalized micelle confers controlled self-assembly behavior

HypothesisInvoking cooperative assembly of the uracil-functionalized supramolecular polymer BU-PPG [uracil end-capped poly(propylene glycol)] upon association with the nucleobase adenine derivative A-MA [methyl 3-(6-amino-9H-purin-9-yl)propanoate] as a model drug provides a new concept to control and tune the properties of supramolecular complexes and holds significant potential for the development of safer, more effective drug delivery systems. ExperimentsBU-PPG and A-MA were successfully developed and exhibited specific recognition and high affinity, which enabled reversible complementary adenine-uracil (A-U) hydrogen bonding-induced formation of spherical micelles in aqueous solution. The self-assembly and controllable A-MA release behavior of BU-PPG/A-MA micelles were studied using morphological analysis and optical and light scattering techniques to investigate the effect of photoirradiation and temperature on the complementary hydrogen bond interactions between BU-PPG and A-MA. FindingsThe resulting micelles possess unusual physical properties, including controlled photoreactivity kinetics, controllable self-assembled morphology and low cytotoxicity in vitro, as well as reversible temperature-responsive behavior. Importantly, irradiated micelles exhibited excellent long-term structural stability under normal physiological conditions and serum disturbance. Increasing the temperature triggered rapid release of A-MA by disrupting A-U complexes. These findings represent an entirely new, promising strategy for the development of multi-controlled release drug delivery nanocarriers based on complementary hydrogen bonding interactions.

Liquid-liquid phase separation during amphiphilic self-assembly.

The self-assembly of amphiphilic molecules in solution is a ubiquitous process in both natural and synthetic systems. The ability to effectively control the structure and properties of these systems is essential for tuning the quality of their functionality, yet the underlying mechanisms governing the transition from molecules to assemblies have not been fully resolved. Here we describe how amphiphilic self-assembly can be preceded by liquid-liquid phase separation. The assembly of a model block co-polymer system into vesicular structures was probed through a combination of liquid-phase electron microscopy, self-consistent field computations and Gibbs free energy calculations. This analysis shows the formation of polymer-rich liquid droplets that act as a precursor in the bottom-up formation of spherical micelles, which then evolve into vesicles. The liquid-liquid phase separation plays a role in determining the resulting vesicles' structural properties, such as their size and membrane thickness, and the onset of kinetic traps during self-assembly.

Polymerization-Induced Self-Assembly of Micelles Observed by Liquid Cell Transmission Electron Microscopy.

In this paper, we describe the use of liquid cell transmission electron microscopy (LCTEM) for inducing and imaging the formation of spherical micelles from amphiphilic block copolymers. Within the irradiated region of the liquid cell, diblock copolymers were produced which self-assembled, yielding a targeted spherical micellar phase via polymerization-induced self-assembly (PISA). Critically, we demonstrate that nanoparticle formation can be visualized in situ and that in the presence of excess monomer, nanoparticle growth occurs to yield sizes and morphologies consistent with standard PISA conditions. Experiments were enabled by employing automated LCTEM sample preparation and by analyzing LCTEM data with multi-object tracking algorithms designed for the detection of low-contrast materials.

Preparation and evaluation of PCL-PEG-PCL micelles as potential nanocarriers for ocular delivery of dexamethasone.

Objective(s):Micelles have been studied as nanoparticulate drug delivery systems for improving the topical ocular delivery of hydrophobic drugs. The objective of this study was to develop and characterize dexamethasone-loaded polycaprolactone-polyethylene glycol-polycaprolactone (PCL-PEG-PCL) micelles to improve patient compliance and enhance the ocular bioavailability of poorly water-soluble drugs.Materials and Methods:The PCL-PEG-PCL copolymers were synthesized via the ring opening polymerization of ε-caprolactone in the presence of PEG. The resulting purified copolymers were characterized by GPC, NMR, FTIR, XRD and DSC. The critical micelle concentrations (CMCs) of the mentioned copolymers were determined. Dexamethasone was loaded into polymeric micelles by film hydration method, and dexamethasone-loaded micelles were characterized by TEM and DLS. Drug release kinetics and ex vivo corneal permeability were also determined.Results:The CMC of the synthetized copolymers was approximately 0.03 mg/ml. Aqueous solutions of the resulting copolymers (400 mg/ml) rapidly formed a gel in situ at 34°C. The TEM results exhibited the successful formation of spherical micelles. The size of the prepared micelles was approximately 40 nm. Formulated micelles sustained the release of the incorporated dexamethasone for 5 days.Conclusion:Data from ex vivo permeability tests indicated that PCL-PEG-PCL micelles can be suitable candidates for the ocular delivery of dexamethasone and, likely, other hydrophobic drugs.

Self‐assembled micelles prepared from poly(ɛ‐caprolactone)–poly(ethylene glycol) and poly(ɛ‐caprolactone/glycolide)–poly(ethylene glycol) block copolymers for sustained drug delivery

ABSTRACTA series of poly(ɛ‐caprolactone)–poly(ethylene glycol) (PCL‐PEG) and poly(ɛ‐caprolactone/glycolide)–poly(ethylene glycol) [P(CL/GA)‐PEG] diblock copolymers were prepared by ring‐opening polymerization of ɛ‐caprolactone or a mixture of ɛ‐caprolactone and glycolide using monomethoxy PEG (mPEG) as macroinitiator and Sn(Oct)2 as catalyst. The resulting copolymers were characterized using 1H‐NMR, gel permeation chromatography, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Copolymer micelles were prepared using the nanoprecipitation method. The morphology of the micelles was spherical or worm‐like as revealed by transmission electron microscopy, depending on the copolymer composition and the length of the hydrophobic block. Introduction of the glycolide component, even in small amounts (CL/GA = 10), disrupted the chain structure and led to the formation of spherical micelles. Interestingly, the micelle size decreased with the encapsulation of paclitaxel. Micelles prepared from mPEG5000‐derived copolymers exhibited better drug loading properties and slower drug release than those from mPEG2000‐derived copolymers. Drug release was faster for copolymers with shorter PCL blocks than for those with longer PCL chains. The introduction of glycolide moieties enhanced drug release, but the overall release rate did not exceed 10% in 30 days. In contrast, drug release was enhanced in acidic media. Therefore, these bioresorbable micelles and especially P(CL/GA)‐PEG micelles with excellent stability, high drug loading content, and prolonged drug release could be promising for applications as drug carriers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45732.

Facile One‐Pot Synthesis of Functional Giant Polymeric Vesicles Controlled by Oscillatory Chemistry

AbstractWe introduce a novel application of an oscillatory chemical reaction to the synthesis of block copolymers. The Belousov–Zhabotinsky (B‐Z) reaction is coupled with the polymerization of an amphiphilic block copolymer. Radicals generated in the B‐Z reaction initiate the polymerization between a polyethylene glycol (PEG) macroreversible addition‐fragmentation chain‐transfer agent and butyl acrylate monomers. The attachment of a hydrophobic block on PEG leads to self‐assembly and formation of spherical micelles. The nanoscale micelles transform into submicrometer vesicles and grow to giant vesicles as a consequence of the oscillatory behavior of the B‐Z reaction. The one‐pot synthesis of an amphiphilic di‐block copolymer and retention of oscillatory behavior for the B‐Z reaction with the formation of giant vesicles bring a new insight into possible pathways for the synthesis of active functional microreactors in the range from hundreds of nanometers to tens of micrometers.