Synthesis and Characterization of Amphiphilic Poly(ethylene oxide)‐block‐poly(hexyl methacrylate) Copolymers

We describe the preparation of amphiphilic diblock copolymers made of poly(ethylene oxide) (PEO) and poly(hexyl methacrylate) (PHMA) synthesized by anionic polymerization of ethylene oxide and subsequent atom transfer radical polymerization (ATRP) of hexyl methacrylate (HMA). The first block, PEO, is prepared by anionic polymerization of ethylene oxide in tetrahydrofuran. End capping is achieved by treatment of living PEO chain ends with 2‐bromoisobutyryl bromide to yield a macroinitiator for ATRP. The second block is added by polymerization of HMA, using the PEO macroinitiator in the presence of dibromobis(triphenylphosphine) nickel(II), NiBr₂(PPh₃)₂, as the catalyst. Kinetics studies reveal absence of termination consistent with controlled polymerization of HMA. GPC data show low polydispersities of the corresponding diblock copolymers. The microdomain structure of selected PEO‐block‐PHMA block copolymers is investigated by small angle X‐ray scattering experiments, revealing behavior expected from known diblock copolymer phase diagrams.

SAXS diffractograms of PEO‐block‐PHMA diblock copolymers with 16, 44, 68 wt.‐% PEO showing spherical (A), cylindrical (B), and lamellae (C) morphologies, respectively.     

Nanostructure and Shape Control in Polymer‐Ceramic Hybrids from Poly(ethylene oxide)‐block‐Poly(hexyl methacrylate) and Aluminosilicates Derived from Them

Summary: The present study describes the use of poly(ethylene oxide)‐block‐poly(hexyl methacrylate) diblock copolymers (PEO‐b‐PHMA) as structure‐directing agents for the synthesis of nanostructured polymer‐inorganic hybrid materials from (3‐glycidylpropyl)trimethoxysilane and aluminium sec‐butoxide as precursors and organic, volatile solvents. Four different morphologies, i.e., inorganic spheres, cylinders, lamellae, and organic cylinders in an inorganic matrix, are obtained confirmed by a combination of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The composites are further characterized by differential scanning calorimetry (DSC) and solid‐state ¹³C, ²⁹Si, and ²⁷Al NMR. It is demonstrated that the change in the hydrophobic block from polyisoprene (PI) to poly(hexyl methacrylate) (PHMA) has no significant effect on the local structure of the inorganic rich phase. By the dissolution of the composites rich in poly(hexyl methacrylate), nano‐particles of different shapes, i.e., spheres, cylinders, and lamellae, are obtained as demonstrated by atomic force microscopy (AFM) and TEM. Finally, calcination of composites with the inverse hexagonal structure at elevated temperatures up to 600 °C results in nanostructured aluminosilicates that retain their structure as evidenced through a combination of SAXS and TEM. The study opens pathways towards tailoring filler‐matrix interactions in model nanocomposites and builds the bases for the preparation of composites from multiblock copolymers with polyisoprene (PI), poly(ethylene oxide) (PEO), and poly(hexyl methacrylate) (PHMA) as building blocks.

Bright field TEM micrograph of composite T55/1 with inverse hexagonal morphology after calcination.     

Micelle formation of poly(acrylic acid)-block-poly(methyl methacrylate) block copolymers in mixtures of water with organic solvents

The micelle formation of poly(acrylic acid)-block-poly(methyl methacrylate) (AA-MMA) block copolymers in mixtures of water with organic solvents was investigated by non-radiative energy transfer (NRET). In the case of block copolymers with 70 hydrophobic MMA units, which form strongly aggregated micelles in pure water, the addition of a non-selective organic solvent (methanol or 1,4-dioxane) induces a micelle-unimer transition within a relatively small range of solvent composition without significantly increasing the rate of chain exchange between micelles close to this transition region. The addition of 2 vol.-% dimethyl adipate (a solvent with chemical similarity to the PMMA block and only limited solubility in water) does not speed up the chain exchange in this system either. In contrast, this solvent promotes the aggregation of smaller block copolymers (20 or 40 MMA units) which are mainly present as single chains in pure water. In the case of the block copolymer with 40 MMA units the so formed micelles show a very slow chain exchange extending over many days. These observations prompt us to assume that the rate of the micelle-unimer exchange equilibrium is not kinetically hindered (i. e., determined by the T_g of the core material of the micelle) but controlled by a strong thermodynamic preference for the aggregated state.     

Synthesis of ethylene oxide/methyl methacrylate diblock copolymers by group transfer polymerization of methyl methacrylate with poly(ethylene oxide) macroinitiators

Ethylene oxide/methyl methacrylate diblock copolymers were prepared by group transfer polymerization (GTP) of methyl methacrylate (MMA) with poly(ethylene oxide) macroinitiators ( 1 ). The macroinitiator containing silyl ketene acetal end-groups was synthesized by hydrosilation of poly(ethylene glycol) monomethacrylate which was previously prepared by esterification of poly(ethylene glycol) monomethyl ether (PEO OH). All synthesized macroinitiators initiated the GTP of MMA in tetrahydrofuran with tetrabutylammonium cyanide or tris(dimethylamino)sulfonium difluoride as catalysts. The polymerization proceeds rapidly at room temperature to quantitative yield. The block copolymers are contaminated with small fractions of PEO homopolymer as a result of uncomplete macroinitiator synthesis. Unreacted PEO—OH, which is present in very small amounts, reduces the concentration of active centers. Therefore, the degree of polymerization is not in good agreement with the theoretical value calculated for a living polymerization taking the monomer to macroinitiator ratio. However, after extraction of the PEO homopolymer, the block copolymers show a narrow molecular weight distribution. Induction periods in time-conversion curves obtained with 1 as initiator vanished nearly, when the reaction was started with the addition product of 1 and MMA. This is an indication, that in the system under investigation a slow initiation step between 1 and the first MMA unit precedes the propagation reaction. Tacticity measurements yield about 56% syndiotactic, 40% heterotactic and 4% isotactic triads for PMMA in the block copolymers.     

Spherical Compound Micelles with Lamellar Stripes Self‐Assembled from Star Liquid Crystalline Diblock Copolymers in Solution

Detailed investigations on the self‐assembly of amphiphilic star block copolymers composed of three‐arm poly(ethylene oxide) (PEO) and poly(methacrylate) (PMAAz) with an azobenzene side chain (denoted as 3PEO‐b‐PMAAz) into stable spherical aggregates with clear lamellar stripes in solution are demonstrated. Four block copolymers, 3PEO₁₂‐b‐PMA(Az)₃₃, 3PEO₂₂‐b‐PMA(Az)₃₁, 3PEO₂₂‐b‐PMA(Az)₆₂, and linear PEO₆₈‐b‐PMA(Az)₃₁, are synthesized. The liquid crystalline properties of the block copolymers are studied by differential scanning calorimetry, polarized optical microscopy techniques, and wide‐angle X‐ray diffraction. The morphologies of the compound micelles self‐assembled in tetrahydrofuran (THF)/water mixtures are observed by means of transmission electron microscopy and scanning electron microscopy. The size of the spherical micelles is influenced by the self‐assembly conditions and the lengths of two blocks. The well‐defined three‐arm architecture of the hydrophilic blocks is a key structural element to the formation of stable spherical compound micelles. The micelle surface integrity is affected by the lengths of PEO blocks. The lamellar stripes are clearly observed on these micelles. This work provides a promising strategy to prepare functional stable spherical compound micelles self‐assembled by amphiphilic block copolymers in solution.     

Janus Micelle Formation Induced by Protonation/Deprotonation of Poly(2‐vinylpyridine)‐block‐Poly(ethylene oxide) Diblock Copolymers

A novel approach to amphiphilic polymeric Janus micelles based on the protonation/deprotonation process of poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (P2VP‐b‐PEO) diblock copolymers in THF is presented. It is found that addition of HCl to the micelles solution of P2VP‐b‐PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl₄ precursors, composite Janus particles containing gold in P2VP blocks are obtained.

     

Poly(hydroxyl propyl methacrylate)‐b‐Poly(oligo ethylene glycol methacrylate) Thermoresponsive Block Copolymers by RAFT Polymerization

Thermoresponsive amphiphilic poly(hydroxyl propyl methacrylate)‐b‐poly(oligo ethylene glycol methacrylate) block copolymers (PHPMA‐b‐POEGMA) are synthesized by RAFT polymerization, with different compositions and molecular weights. The copolymers are molecularly characterized by size‐exclusion chromophotography, and ¹H NMR spectroscopy. Dynamic light scattering (DLS) and static light scattering (SLS) experiments in aqueous solutions show that the copolymers respond to temperature variations via formation of self‐organized nanoscale aggregates. Aggregate structural characteristics depend on copolymer composition, molecular weight, and ionic strength of the solution. Fluorescence spectroscopy experiments confirm the presence of less hydrophilic domains within the aggregates at higher temperatures. The thermoresponsive behavior of the PHPMA‐b‐POEGMA block copolymers is attributed to the particular solubility characteristics of the hydrophilic, water insoluble PHPMA block that are modulated by the presence of the water soluble POEGMA block.     

Synthesis and characterization of poly(ethylene oxide) and poly(perfluorohexylethyl methacrylate) containing triblock copolymers

A new series of poly(perfluorohexylethyl methacrylate)‐block‐poly(ethylene oxide)‐block‐poly(perfluorohexylethyl methacrylate), PFMA‐b‐PEO‐b‐PFMA triblock copolymers has been synthesized by atom transfer radical polymerization using bifunctional PEO macroinitiators. The molecular structure of the block copolymers was confirmed by ¹H NMR spectroscopy and SEC. X‐ray scattering studies have been carried out to investigate their bulk properties. SAXS has shown cubic arrangement of spheres (bcc), hexagonally packed cylinders (hpc) and lamellar microdomain formation in the melt of triblock copolymers investigated, depending on composition. Crystallization was, however, found to destroy the ordered melt morphology and imposes a lamellar crystalline structure. WAXS, DSC and polarized light microscopy measurements confirmed the crystallization of PEO segments in block copolymers. Long PFMA blocks were found to have significant effect on PEO crystallization.

Synthesis of triblock copolymers of EO and FMA by ATRP.     

Self‐Assembled Acrylic ABA Triblock Copolymer Hydrogels with Various Block Compositions: Water Absorbency,Rheology, and SAXS

A series of well‐defined symmetric poly(methyl methacrylate)‐b‐poly(sodium methacrylate)‐b‐poly(methyl methacrylate) (PMMA‐b‐PSMA‐b‐PMMA) triblock copolymers with various block compositions is synthesized. The amphiphilic ABA triblock copolymers form polyelectrolyte hydrogels in water by self‐assembly. The hydrophobic PMMA endblocks act as physical cross‐links in the form of frozen micelles, while the hydrophilic PSMA midblocks span the 3D network. The influence of various synthetic parameters on the self‐assembly and the macroscopic properties of these hydrogels is systematically investigated by water absorbency, oscillatory shear rheology, and small‐angle X‐ray scattering. The polymer concentration during the hydrogel formation affects the ratio between looping and bridging chains. The number of MMA units per endblock (n_A) determines the size and the relaxation rates of the physical cross‐links and thus, the mechanical stability of the hydrogels. More SMA units in the midblock (n_B) increase the water absorbency, while the mechanical moduli decrease. Even lower G‐moduli are achieved by partly exchanging the symmetric ABA triblock with AB diblock copolymers, which can only form non‐elastic dangling ends.     

Small‐Angle Neutron Scattering Study of Onion‐Type Micelles

Onion‐type block copolymer micelles were prepared from polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐PVP) inner micelles in an acidic solution by basifying in the presence of poly(2‐vinylpyridine)‐block‐poly‐(ethylene oxide) (PVP‐b‐PEO). This has the effect of depositing the PVP‐b‐PEO onto the collapsed corona of the PS‐b‐PVP micelle. These core PS‐b‐PVP micelles, the small micelles formed by PVP‐b‐PEO, and the resulting onion micelles were studied by small angle neutron scattering (SANS) techniques. Two recently developed evaluation techniques were employed: 1.Bare‐core approximation, which utilizes the data at larger scattering angles and provided information about the size and polydispersity of the micelle cores. 2. Application of the Pedersen and Gerstenberg micelle model, which utilizes the whole scattering curve. Due to their polyelectrolyte nature, the core micelles had very extended coronas corresponding to rather large statistical segment lengths. The SANS data at large scattering angles for the solution of onion‐type micelles revealed the presence of a significant number of the small PVP‐b‐PEO micelles. The contribution of the small micelles to the total scattering was subtracted and the properties and polydispersities of onion cores and stabilizing PEO coronas were obtained.     

Calcium Alcoholates of Hydroxytelechelic Poly(ethylene oxide)s as Initiators for the Ring‐Opening Polymerization of 3‐(S)‐Isopropylmorpholine‐2,5‐dione

Block copolymers with poly[3‐isopropylmorpholine‐2,5‐dione] (PIPMD) and poly(ethylene oxide) (M̄_n = 6 000, PEO) blocks, PIPMD‐b‐PEO‐b‐PIPMD, were synthesized via the ring‐opening polymerization of 3‐(S)‐isopropylmorpholine‐2,5‐dione (IPMD) in the presence of the calcium alcoholate of hydroxytelechelic poly(ethylene oxide) as an initiator at 140°C within 24 or 96 h. The number‐average molecular weight (M̄_n) of the resulting copolymers increases with increasing IPMD content in the feed and with reaction time. According to ¹H NMR spectroscopic analysis, about 40% of IPMD is racemized during polymerization within 96 h at 140°C, while about 12% is racemized within 24 h. The melting temperature of the PEO block upon first heating is lower than that of pure PEO homopolymer, and the melting endotherm decreases with increasing length of the PIPMD block upon second heating.     

Poly(ethylene oxide)‐ and Poly(perfluorohexylethyl methacrylate)‐Containing Amphiphilic Block Copolymers: Association Properties in Aqueous Solution

Amphiphilic di‐ and triblock copolymers containing poly(ethylene oxide) (PEO) as the hydrophilic block and poly(perfluorohexylethyl methacrylate) (PFMA) as the hydrophobic block were synthesized by atom‐transfer radical polymerization using hydroxy‐terminated PEO as the macroinitiator. The copolymers were characterized by size exclusion chromatography and ¹H NMR spectroscopy. Self‐association in aqueous solution has been investigated using surface tension measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). From surface tension measurements in water, a characteristic concentration (c*) can be detected, which is interpreted as the critical micelle concentration (cmc). The cmc decreases with an increase in fluoro content in the triblock copolymer up to 11 wt.‐% PFMA (solubility limit). DLS studies have been carried out for different samples above the cmc, showing small aggregates (micelles) and single chains for diblock copolymer solutions. In the case of triblock copolymers large clusters were the dominant aggregates in addition to the micelles and single chains. The effect of temperature and concentration on the micelle and cluster formation has been investigated by DLS. Micelle size was found to be resistant to any change by temperature, however, a slight but significant increase in apparent hydrodynamic radius was observed with an increase in concentration, while both temperature and concentration affected the formation of large clusters, especially in concentrated solutions. TEM has been carried out to visualize the morphology of the aggregates after transferring the solution to carbon film. The initial concentration for the preparation of TEM samples was found to have a strong influence on the morphology of the aggregates. By adding colloidal gold particles to the solutions, the typical covering by the polymer was observed by TEM.

Decay‐rate distributions for PEO₁₀F5 (4.0 g · L^?1); obtained from the time correlation functions.     

Poly(ε‐caprolactone) Single Crystals with Different Aspect Ratios Mediated by Counterion Exchange on the Basis of Hofmeister Series

Although polymeric single crystals fabricated from self‐assembly of block copolymers are reported, preparation of single crystals with different aspect ratios still remains a major challenge. In this work, a facile way is demonstrated to prepare poly(ε‐caprolactone) based single crystals with tunable aspect ratios through simple counterion exchange on the basis of the Hofmeister series. Briefly, after ion exchange from Brˉ (an ion‐containing triblock copolymer, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(quaternized 2‐(dimethylamino)ethyl methacrylate)/ethyl bromide (PEO‐b‐PCL‐b‐qPDM‐Br)) to more hydrophobic anions, Iˉ, SCNˉ, PF₆ˉ and OTfˉ, respectively, morphological transitions from spheres to wormlike micelles and sphere to 2D platelet structure with an increasing aspect ratio are observed. The morphological transition depends on the essential hydrophilicity of the qPDM‐X segment and increasing crystallinity of the PCL core caused by ion exchange. These findings provide a facile approach to the preparation of polymeric single crystals with tunable aspect ratios.     

Effect of Sonication on Polymeric Aggregates Formed by Poly(ethylene oxide)‐Based Amphiphilic Block Copolymers

The effect of sonication on the size and structure of polymeric aggregates formed by amphiphilic block copolymers was studied by the combination of dynamic and static light scattering. Poly(ethylene oxide)‐block‐polyisoprene, poly(ethylene oxide)‐block‐polystyrene diblock copolymers, and poly(ethylene oxide)‐block‐polyisoprene‐block‐poly(ethylene oxide) triblock copolymer were used as typical polymeric amphiphiles. Sonication was found to be an effective method to break up inter‐micellar associations and split large polymeric aggregates, present initially in the aqueous solutions, into monodisperse micelles. The content and type of hydrophobic block, copolymer solution‐preparation protocol, and copolymer concentration were also investigated as co‐factors in conjunction to the effect of sonication time.

     

Allyl End‐Functionalized Poly(ethylene oxide)‐block‐poly(methylidene malonate 2.1.2) Block Copolymers: Synthesis,Characterization, and Chemical Modification

Summary: Poly(ethylene oxide)‐block‐poly(methylidene malonate 2.1.2) block copolymer (PEO‐b‐PMM 2.1.2) bearing an allyl moiety at the poly(ethylene oxide) chain end was synthesized by sequential anionic polymerization of ethylene oxide (EO) and methylidene malonate 2.1.2 (MM 2.1.2). This allyl functional group was subsequently modified by reaction with thiol‐bearing functional groups to generate carboxyl and amino functionalized biodegradable block copolymers. These end‐group reactions, performed in good yields both in organic media and in aqueous micellar solutions, lead to functionalized PEO‐b‐PMM 2.1.2 copolymers which are of interest for cell targeting purposes.

Synthetic route to α‐allyl functionalized PEO‐b‐PMM 2.1.2 copolymers.     

Bioinspired Photo‐Core‐Crosslinked and Noncovalently Connected Micelles From Functionalized Polystyrene and Poly(ethylene oxide) Homopolymers

In this paper, we report a simple and effective method for the preparation of stable core‐crosslinked micelles after the self‐assembly of thymine‐functionalized polystyrene (PVBT) and adenine‐terminated poly(ethylene oxide) (PEO‐A) homopolymers, and subsequent bioinspired photo‐crosslinking of the thymine units in PVBT. We obtained “graft‐like” copolymers from the interactions of PEO‐A with the PVBT chains through complementary multiple hydrogen bonding in a common solvent (dimethylformamide) after the addition of selective solvents (H₂O and MeCN for PVBT and PEO‐A, respectively). Stable micelles featuring PVBT as the core and PEO‐A as the shell were formed via selective solvent pairs; they were clearly visualized using transmission electronic microscopy and staining techniques. The shapes and sizes of the core/shell micelle structures did not change after exposure to UV light, revealing the enhanced dimensional stability of these photo‐core‐crosslinked micelles.     

Aggregation Behavior of Polystyrene/Poly(acrylic acid) Heteroarm Star Copolymers in 1,4‐Dioxane and Aqueous Media

Ionic heteroarm star copolymers bearing polystyrene (PS) and poly(acrylic acid) (PAA) arms (PS_nPAA_n) were prepared by quantitative hydrolysis of the poly(tert‐butyl acrylate) (PtBA) arms of the corresponding PS_nPtBA_n star copolymer. The aggregation properties of these copolymers were studied in various solvents. In 1,4‐dioxane PS₁₂PAA₁₂ (with nearly symmetrical PS and PAA arms) forms reverse micelles of low aggregation number (N_agg) and spherical morphology. In an 80 : 20 (v/v) 1,4‐dioxane/water mixture these micelles are transformed to regular micelles with an unexpectedly high N_agg and an elongated rod‐like structure. An abnormal behavior was observed in aqueous solutions of charged PS₂₄PANa₂₄ (with asymmetrical PS and PAA arms, W_PS = 19 wt.‐%) at low concentrations. A non‐equilibrium physical gel is formed, characterized by a very high viscosity and an elastic response upon oscillatory shearing.     

Double Hydrophilic Poly(ethylene oxide)‐block‐Poly(dehydroalanine) Block Copolymers: Comparison of Two Different Synthetic Routes

Two different synthetic pathways give access to the amphiphilic block copolymer poly(ethylene oxide)‐block‐poly(tert‐butoxycarbonylaminomethylacrylate). In the first approach, two end‐functionalized segments are linked via click chemistry; and in the second approach, a poly(ethylene oxide) (PEO) based macroinitiator is chain extended via atom transfer radical polymerization (ATRP). In both cases the linking unit consists of an amide group, which is necessary to effectively deprotect the corresponding polymer precursor without cleavage of both segments. For this, amide‐containing ATRP initiators are employed and successful synthesis by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC) analyses before comparing both pathways is demonstrated. After deprotection, a novel double hydrophilic block copolymer, poly(ethylene oxide)‐block‐poly(dehydroalanine), is obtained, which is investigated using SEC (aqueous and DMSO) and ¹H‐NMR spectroscopy. Containing a potentially zwitterionic PDha segment and a high density of both amino and carboxylic groups, pH‐dependent aggregation of the block copolymer is expected and is studied using dynamic light scattering, revealing interesting solution properties. The corresponding polymers are applied in various areas including drug delivery systems or in biomineralization.     

Association Behavior between End‐Functionalized Block Copolymers PEO‐PPO‐PEO and Poly(acrylic acid)

Summary: The end groups of ABA‐triblock copolymers HO–PEO–PPO–PEO–OH, (PEO – poly(ethylene oxide), PPO – poly(propylene oxide)), have been modified with ammonia, ethylene diamine and linear polyethylenimine (LPEI) by substitution of the α,ω‐ditosyl ester of the triblock copolymer (TsO–PEO–PPO–PEO–OTs) with amines, or by the hydrolysis of the corresponding poly(2‐methyl‐2‐oxazoline) (PMeOx) containing ABCBA block copolymers. The latter block copolymer structures have been obtained by the polymerization of MeOx using TsO–PEO–PPO–PEO–OTs as a macro‐initiator. Adding poly(acrylic acid) (PAA) to these (poly)amine terminated block copolymers leads to the formation of networks through a combination of PAA–PEO hydrogen bonding and PAA–(poly)amine acid‐base reaction. Depending on the number of amino groups at both chain ends of the block copolymer, the corresponding complexes behave as liquids, gels or precipitates. Introduction of as little as 1–5 wt.‐% block copolymers H₂N–PEO–PPO–PEO–NH₂ or H₂NCH₂CH₂NH–PEO–PPO–PEO–NHCH₂CH₂NH₂ to the system of HO–PEO–PPO–PEO–OH/PAA leads to viscous liquids with strong shear‐thickening behavior.

Reversible gel formation via the ternary PAA/HO–PEO–PPO–PEO–OH/H₂N–PEO–PPO–PEO–NH₂ system under shear conditions.     

Folate‐Conjugated Poly(N‐(2‐hydroxypropyl) methacrylamide)‐block‐Poly(benzyl methacrylate): Synthesis,Self‐Assembly,and Drug Release

Well‐defined amphiphilic diblock copolymers of poly(N‐(2‐hydroxypropyl)methacrylamide)‐block‐poly(benzyl methacrylate) (PHPMA‐b‐PBnMA) are synthesized using reversible addition–fragmentation chain transfer polymerization. The terminal dithiobenzoate groups are converted into carboxylic acids. The copolymers self‐assemble into micelles with a PBnMA core and PHPMA shell. Their mean size is <30 nm, and can be regulated by the length of the hydrophilic chain. The compatibility between the hydrophobic segment and the drug doxorubicin (DOX) affords more interaction of the cores with DOX. Fluorescence spectra are used to determine the critical micelle concentration of the folate‐conjugated amphiphilic block copolymer. Dynamic light scattering measurements reveal the stability of the micelles with or without DOX. Drug release experiments show that the DOX‐loaded micelles are stable under simulated circulation conditions and the DOX can be quickly released under acidic endosome pH.