The beneficial effect of small amount of water in the ambient temperature atom transfer radical homo and block co-polymerization of methacrylates

ATRP of several methacrylates viz. methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), t-butyl methacrylate (tBMA), benzyl methacrylate (BzMA) and (N,N-dimethylamino)ethyl methacrylate (DMAEMA) has been studied in neat as well as aqueous (up to 12 vol% water) acetone at 35 °C using CuCl/bipyridine (bpy) catalyst and ethyl 2-bromoisobutyrate as the initiator. Addition of water significantly enhances the rate of polymerization without losing control. Unlike CuCl/bpy the CuBr/bpy catalyst gives poor control which is attributed to the lower solubility and consequent heterogeneity in the latter case. Of the other ligands used with the CuCl catalyst viz. o-phenanthroline (o-phen), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), Me₆TREN only o-phen offers reasonably good control. The CuCl/bpy catalyst system has been used also in preparing some di- and tri-block copolymers with reasonably low polydispersity index (PDI) at ambient temperature (35 °C) using aqueous acetone as the solvent. The following block copolymers have been prepared PMMA-tBMA, PMMA-b-tBMA-b-MMA, PMMA-DMAEMA, by this method.     

New water soluble azobenzene-containing diblock copolymers: synthesis and aggregation behavior

Homopolymers of azobenzene (azo) methacrylates with different substituents and their diblock copolymers with poly(2-(dimethylamino)ethyl methacrylate p(DMAEMA) were synthesized via atom transfer radical polymerization (ATRP). Controlled/‘living’ ATRP of azo methacrylates were achieved up to ∼50% conversion, after which deviation occurred. It was found that the copolymerization rate of 6-[4-phenylazo]phenoxy]hexylmethacrylate (PPHM) from p(DMAEMA) macroinitiator was almost identical to that for the homopolymerization of PPHM monomer, with k_app∼0.0078 min⁻¹. For the copolymerizations, almost complete incorporation of the azo methacrylate monomers could be obtained with low molecular weight macroinitiator (PDMAEMA)-Cl, whereas macroinitiators of long chain length did not give full conversion, most likely due to chain floding and steric hindrance caused by the bulk azo monomers. Because azo monomers are highly hydrophobic, only the diblock copolymers with short azo segment were soluble in water which self-assembled into micellar particles. The effect of photo-induced trans-cis isomerization on lower critical solution temperature (LCST) and surface tension were studied. The LCST of the diblock copolymers increased upon irradiation by UV light due to the cis conformers being more hydrophilic. However, the trans-cis isomerization had only small effect on the critical micelle concentration (cmc) and γ_cmc of azo methacrylate block copolymers, due to the formation of compact core of the micelles. The formations of core-shell micelles were established from LLS and TEM studies. All the three azo methacrylate amphiphilic block copolymers formed hard core-shell micelles with relatively small R_h values of 31 nm for p(DMAEMA₁₇₂-b-BPHM₇), 26 nm for p(DMAEMA₁₇₂-b-CPHM₇) and 32 nm for p(DMAEMA₁₇₂-b-PPHM₉). Whereas for the azo acrylate copolymer, p(DMAEMA₁₇₂-b-BPHA₆), large micelles with R_h∼78 nm with loose core was formed.     

Preparation and properties of semifluorinated block copolymers of 2-(dimethylamino)ethyl methacrylate and fluorooctyl methacrylates

Semifluorinated block copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(fluorooctyl methacrylates) (PFOMA) were prepared using group transfer polymerisation via sequential monomer addition. Wide ranges of copolymers were obtained with good control over both molecular weight and composition by adjusting the monomers/initiator ratio. The micellar characteristics of the copolymers in water and chloroform were investigated by quasi-elastic light scattering and transmission electron microscopy. The size and morphologies of micelles were greatly influenced by copolymer composition, pH, and temperature. In addition, the solubility of copolymers and the formation of water-in-carbon dioxide (W/C) microemulsions were described in terms of the cloud points. The block copolymers exhibited the excellent ability of stabilizing W/C microemulsions.     

Synthesis and pH-dependent micellization of 2-(diisopropylamino)ethyl methacrylate based amphiphilic diblock copolymers via RAFT polymerization

The polymerization of 2-(diisopropylamino)ethyl methacrylate (DPA) by RAFT mechanism in the presence of 4-cyanopentanoic acid dithiobenzoate in 1,4-dioxane was studied. The DPA homopolymer was employed as a macro chain transfer agent to synthesize pH-sensitive amphiphilic block copolymers using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the hydrophilic block. ¹H NMR and GPC measurements confirmed the successful synthesis of these copolymers. Potentiometric titrations and fluorescence experiments proved that the copolymers underwent a sharp transition from unimers to micelles at a pH of ∼6.7 in phosphate buffered saline solutions. It was found that the hydrophilic/hydrophobic balance of these block copolymers had no apparent effect on their pH-induced micellization behaviors. The DLS investigation revealed that the micelles have a mean hydrodynamic diameter below 60 nm with a narrow size distribution.     

Synthesis and aqueous solution characterization of amphiphilic diblock copolymers containing carbazole

A series of near-monodisperse diblock copolymers of 2-(N-carbazolyl)ethyl methacrylate and 2-(dimethylamino)ethyl methacrylate (DMAEMA) of relatively low molecular weights (2600-24,000 g mol⁻¹) were synthesized by group transfer polymerization using tetrahydrofuran (THF) as a solvent. The molecular weight distributions and compositions of all the copolymers were obtained using gel permeation chromatography (GPC) in THF and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Differential scanning calorimetry and thermal gravimetric analysis provided low glass transition temperatures (T_gs) of about 60 °C and decomposition temperatures between 320 and 450 °C for the copolymers, respectively. The three copolymers with the highest DMAEMA content were water-soluble below pH 7. Aqueous GPC at pH 3 showed that the water-soluble block copolymers formed micelles with apparent number average molecular weights above 100,000 g mol⁻¹.     

Synthesis and characterization of thermo‐ and pH‐sensitive block copolymers bearing a biotin group at the poly(ethylene oxide) chain end

A poly(ethylene oxide)‐block‐poly(dimethylamino ethyl methacrylate) block copolymer (PEO‐b‐PDMAEMA) bearing an amino moiety at the PEO chain end was synthesized by a one‐pot sequential oxyanionic polymerization of ethylene oxide (EO) and dimethylamino ethyl methacrylate (DMAEMA), followed by a coupling reaction between its PEO amino and a biotin derivative. The polymers were charac terized with ¹H NMR spectroscopy and gel permeation chromatography. Activated biotin, biotin‐NHS (N‐hydroxysuccinimide), was used to synthesize biotin‐PEO‐PDMAEMA. In aqueous media, the solubility of the copolymer was temperature‐ and pH‐sensitive. The particle size of the micelle formed from functionalized block copolymers was determined by dynamic light scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3552–3558, 2006     

Effect of hydrophilic chain length on the aqueous solution behavior of block amphiphilic copolymers PMMA‐b‐PDMAEMA

A series of amphiphilic block copolymers, polymethyl methacrylate (PMMA)‐b‐poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA), were synthesized by atom transfer radical polymerization (ATRP) method. Surface tension, dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic force microscopy (AFM) studies were performed to investigate the aqueous micellar behavior of these block amphiphiles. At a fixed degree of polymerization (DP) of PMMA block (DP = 55), the PDMAEMA block length was found to have a significant influence on the critical micelle concentration (cmc) values and hydrodynamic size of aggregates. An increase in the DP of PDMAEMA from 11 to 337, resulted in a decrease in the cmc from 1.44 × 10^?5 to 5.81 × 10^?7 M (a factor of almost 24.8), and a decrease in the Z (2R_h) from 85.5 to 15.5 nm (pH = 4), respectively. TEM and AFM results indicated that by changing the soluble block lengths, spherical, short rod, crew‐cut, vesicles or large aggregates can be observed in the solution. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Two‐component “Onionlike” micelles with a PPO core,a PDMAEMA shell and a PEO corona: formation and crosslinking

BACKGROUND: Chemical or physical crosslinking of supramolecular assemblies gives them stability in a wide range of environments. Much attention is paid to multilayer (onion‐like) polymeric micelles because their functionality is higher than classic core‐shell micelles. This work reports on the formation and crosslinking of onion‐like micelles prepared by mixing two different block copolymers containing a crosslinkable poly(dimethylaminoethyl methacrylate) (PDMAEMA) block. RESULTS: Block copolymers of a crosslinkable PDMAEMA block were synthesized by atom transfer radical polymerization of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) from poly(propylene oxide) (PPO) or poly(ethylene oxide) (PEO) macroinitiators. The (PDMAEMA₁₃)‐block‐PPO₆₉‐block‐(PDMAEMA₁₃) triblock formed wormlike core‐shell micelles, which were converted into ellipsoidal onion‐like micelles on mixing with the PEO₄₅‐block‐P(DMAEMA₈‐co‐MMA₄) diblock. Onion‐like micelles were crosslinked by quaternization of DMAEMA units. CONCLUSION: Formation of onion‐like micelles by mixing two different AB (ABA) and B′C block copolymers and their subsequent crosslinking is a valuable approach towards stabilized supramolecular assemblies of a higher complexity and functionality than the individual constitutive components. Copyright © 2008 Society of Chemical Industry     

Synthesis of well-defined and near narrow-distribution diblock copolymers comprising PMMA and PDMAEMA via oxyanion-initiated polymerization

In this paper, the possibilities offered by oxyanion-initiated polymerization were exploited to tailor well-defined and near narrow-distribution poly[(dimethylamino)ethyl methacrylate]-b-poly(methyl methacrylate) (PDMAEMA-b-PMMA) AB or BA diblock copolymers that were initiated by potassium benzyl alcoholate (BzOK) and controlled by the sequential addition of the alternative monomers. To clarify the living mechanism for MMA and DMAEMA, a series of MMA and DMAEMA homopolymers with near narrow molecular weight distribution were prepared in our laboratory, respectively. If not quenched, the first living moiety could be subsequently used to yield block copolymers BzO-PDMAEMA-b-PMMA with adding the second feed of monomer to the living system. Using reverse succeeding addition of monomers, another benzyloxy-capped diblock copolymer, i.e. BzO-PMMA-b-PDMAEMA was obtained. The thorough characterization of all these diblock copolymers was investigated from ¹H NMR measurement. The results indicated that the expected molecular structures have been obtained with a good correlation between original monomer-to-initiator molar ratios. GPC analysis showed that PDMAEMA homopolymer and the above mentioned two block copolymers possessed narrow molecular weight distribution in the range of 1.15-1.34, while PMMA homopolymer had a little broad molecular weight distribution of 1.29-1.60. This study shows further evidence that oxyanion-initiated polymerization is a control/‘living’ process, not only suitable for tertiary amino-substituted methacrylates, but also for methyl methacrylate. The critical micelle concentration (cmc) of the diblock copolymer BzO-PDMAEMA-b-PMMA in aqueous solution was attained by surface tension measurement. The effects of different lengths of two segments and pH values on the behavior of solution were investigated.     

Effectiveness of block copolymers as stabilizers for aqueous titanium dioxide dispersions of a high solid content

Copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for the aqueous dispersion of titanium dioxide (80 wt.% solid). The molecular composition of the block copolymers has an effect on the dispersion stability. Triblock copolymers consisting of PMANa outer blocks are unable to stabilize the dispersion. Triblock copolymers of the reverse structure form poorly stable dispersions due to at least partial particle bridging. In the case of non-blocky distribution of the DMAEMA and MANa comonomers in the chains, the stabilization capability is lost. A decrease in the anchoring strength of the diblocks has a deleterious effect on the dispersion stability. Finally, the surface coverage depends on the availability of free copolymer chains (unimers) coexisting with micelles. These trends have been confirmed in a fully formulated paint containing Cu-phthalocyanine pigment.     

Synthesis and physical gels of pH- and thermo-responsive tertiary amine methacrylate based ABA triblock copolymers and drug release studies

A series of novel pH-responsive ABA triblock copolymer gelators have been synthesized by using poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) as the A block and poly[2-(dimethylamino)ethyl methacrylate] (PDMA) as the B block via group transfer polymerization. While the PDPA-b-PDMA-b-PDPA triblock copolymers are molecularly soluble in acidic aqueous media due to protonation of all tertiary amine groups, they formed either gels by the chain-end hydrophobic interactions with relatively high polymer concentration (10 wt%) or near monodisperse “flower” micelles with low polymer concentration at neutral and basic aqueous solutions. The hydrophobic model drug release was studied in a sustained manner from the gels at pH 7.4 by varying the polymer concentration, the polymer molecular weight and the temperature of the medium. Preliminary studies indicate that both slow, sustained release and fast, triggered release of a model hydrophobic drug, dipyridamole, can be achieved by tuning the solution pH, polymer concentration, polymer molecular weight and temperature of the gel.     

Selective betainization of 2-(dimethylamino)ethyl methacrylate residues in tertiary amine methacrylate diblock copolymers and their aqueous solution properties

2-(dimethylamino)ethyl methacrylate (DMA) was block copolymerized in turn with three other tertiary amine methacrylate comonomers, namely 2-(diethylamino)ethyl methacrylate (DEA), 2-(diisopropylamino)ethyl methacrylate (DPA) and 2-(N-morpholino)ethyl methacrylate (MEMA), using group transfer polymerization (GTP). The DMA residues of each of these diblock copolymers were selectively betainized using 1,3-propane sultone under mild conditions to yield a series of novel betaine diblock copolymers. These selectively betainized copolymers could be dissolved molecularly without co-solvents in aqueous media at room temperature, with micellization occurring reversibly on judicious adjustment of the solution pH, temperature or electrolyte concentration. In all three cases, stable block copolymer micelles were formed with betainized-DMA coronas and hydrodynamic diameters of 10-46 nm. The selective betainization of the DMA residues dramatically reduces the surface activity and increase the solubility of the tertiary amine methacrylate block copolymers (DMA-DEA, DMA-DPA and DMA-MEMA).     

Multiple morphologies of a poly(methyl methacrylate)-block-poly(N,N-dimethyl aminoethyl methacrylate) copolymer with pH-responsiveness and thermoresponsiveness

We successfully prepared a series of pH-responsive and thermoresponsive poly(methyl methacrylate) (PMMA)-block-poly(N,N-dimethyl aminoethyl methacrylate (PDMAEMA) copolymers via reversible addition–fragmentation chain-transfer polymerization with PMMA as a macro chain-transfer agent. Control over the chain length of PDMAEMA allowed the morphological transformation of PMMA-b-PDMAEMA. The critical water content and critical micelle concentration also depended on the length of the PDMAEMA block. UV–visible and fluorescence spectrum analyses indicated that the PMMA-b-PDMAEMA copolymer exhibited a lower critical solution temperature type phase transition in water. The particle size of PMMA-b-PDMAEMA was dominated by the pH value, as evidenced by dynamic light scattering and transmission electron microscopy. In addition, the PMMA-b-PDMAEMA copolymers exhibited good reversible thermoresponsive behavior between 33 and 38°C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47972.     

Photophysical properties and self-assembly of triblock copolymer with complexes of positively charged PDMAEMA and oppositely charged chromophores

The self-assembly and photophysical properties of a triblock copolymer with complex mid-block in THF and aqueous solution were investigated in this research. Poly(poly(ethylene glycol) methyl ether methacrylate)-block-poly(2-(dimethylamino ethyl methacrylate)-block- poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA–b–PDMAEMA–b–PPEGMA) triblock copolymer was synthesized by subsequent atom transfer radical polymerizations (ATRP) of DMAEMA and PEGMA. The PDMAEMA blocks were quaternized by a reaction with iodomethane. The complex of the positively charged PDMAEMA chain unit and sodium salt of 1-pyrenebutyric acid was prepared by mixing equimolar amount of the two components in THF/water mixture. Transmission electron microscopy and fluorescence technique results show that the triblock copolymer chains self-assemble into micelles in THF at high concentration. The critical aggregation concentration (CAC) of the triblock copolymer in THF determined by fluorescence technique is 6.8 × 10^?5 M. The triblock copolymer was also able to self-assemble into micelles in water. The value of CAC of the triblock copolymer in water is 2.0 × 10^?5 M. The photophysical properties and self-assembly structures of the triblock copolymer in aqueous solutions were influenced by added sodium chloride. After salt addition, a transition of the assembled structures from micelles to hollow structures was observed.     

Ultra-thin films of cationic amphiphilic poly(2-(dimethylamino)ethyl methacrylate) based block copolymers as surface wettability modifiers

Ultra-thin films of cationic amphiphilic block and statistical copolymers were applied on silica surfaces from aqueous solutions through electrostatic interactions, and the resulting modification in the wettability of the surfaces was studied. A copolymer series from 2-(dimethylamino)ethyl methacrylate with methyl methacrylate and butyl methacrylate was polymerized by ATRP. Subsequently, the conformation of the polymers in aqueous solutions was studied by surface tension measurements, dynamic light scattering, ¹H NMR and cryogenic transmission electron microscopy. Unimeric conformation, equilibrium micelles or frozen micellar structures were observed, depending on polymer composition and the ionic strength of the solution. The polymers were applied on silica from aqueous solutions by either spin coating or adsorption. The formed ultra-thin film surfaces were studied by AFM and water contact angle measurements. The spin-coated surfaces were highly hydrophilic with rapidly dropping contact angles, whereas the surfaces prepared by adsorption had stable water contact angles between 30-60°, depending on polymer. The difference between the spin-coated and adsorbed surfaces is explained by the formation of a monolayer in the adsorbed surfaces.     

Synthesis of Y‐shaped poly(N,N‐dimethylamino‐2‐ethyl methacrylate) and poly(trimethylene carbonate) from a new heterofunctional initiator

A new amphiphilic Y‐shaped copolymer, comprised of hydrophobic Poly(trimethylene carbonate) (PTMC) and hydrophilic Poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDMAEMA), was designed and synthesized by a combination of atom transfer radical polymerization (ATRP) and ring‐opening polymerization (ROP) using a new heterofunctional initiator, Br‐Init‐(OH)₂, bearing one initiation site for ATRP and two for ROP. At first, a new trifunctional core molecule bearing hydroxyl group and bromine moieties, Br‐Init‐(OH)₂, was synthesized via protection followed by esterification reaction of 5‐ethyl‐5‐hydroxymethyl‐2,2‐dimethyl‐1,3‐dioxane with 2‐bromoisobutyryl bromide and deprotection. In the presence of trifunctional core molecule, Br‐Init‐(OH)₂, target Y‐shaped miktoarm star copolymers, (PTMC)₂‐ b‐PDMAEMA, were successfully synthesized by sequence conducting the ROP of TMC and ATRP of DMAEMA. The Y‐shaped copolymers were characterized by ¹H NMR and GPC measurements. Subsequently, the self‐assembly behavior of these copolymers was investigated by dynamic light scattering method and transmission electron microscopy, which indicated that these amphiphilic Y‐shaped copolymers can self‐assemble into micelles and possess distinct pH‐dependent size in aqueous milieu. The results indicate that the amphiphilic Y‐shaped copolymers had the pH‐responsive properties similar to the expected PDMAEMA. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Brush-type amphiphilic polystyrene-g-poly(2-(dimethylamino)ethyl methacrylate)) copolymers from ATRP and their self-assembly in selective solvents

A series of well-defined brush-type amphiphilic polystyrene-g-poly(2-(dimethylamino) ethyl methacrylate)) (PS-g-PDMAEMA) copolymers were successfully synthesized via atom transfer radical polymerization (ATRP), using chloromethylated polystyrene (CMPS) as the macroinitiator. The self-assembly behavior of the resulting brush-type copolymers in deionized water and deionized water/acetone (v/v=2/3) mixture was studied by high performance particle sizer (HPPS). The results showed that the Z-average size of the micelles in deionized water increased with the increase of molecular weight of PDMAEMA, and the corresponding size was larger than that in mixed solvent of deionized water and acetone (v/v=2/3). The morphologies of the micelles self-assembled from PS-g-PDMAEMA in selective solvents were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When the micelles were prepared in water/acetone (v/v=2/3) mixture and cast them on a glass slide at different temperatures (from 50 up to 200 °C), the transformation of the morphologies of aggregates, from needle-like solid to microcubic particles, was observed using SEM.     

Micelles and ‘reverse micelles’ with a novel water-soluble diblock copolymer

A series of poly[2-(diisopropylamino)ethyl methacrylate]-block-poly[2-(N-morpholino)ethyl methacrylate], [PDPA-b-PMEMA], have been synthesized by using group transfer polymerization. These novel PDPA-b-PMEMA diblock copolymers dissolved molecularly in aqueous solution at low pH (<6.0) due to the protonation of all tertiary amine residues of both blocks and formed PDPA-core micelles at pH 7.5 by PMEMA block forming the micelle coronas. On the other hand, it was also observed that these diblock copolymers formed near-monodisperse ‘reverse micelles’, PMEMA-core micelles, in n-alkanes with or without requiring cosolvent depending on comonomer ratios. Dynamic light scattering studies indicated monodisperse or near-monodisperse micelles in both cases. The intensity-average radii of the PDPA-core and the PMEMA-core micelles were between 10 nm and 17 nm (polydispersity index, μ₂/Γ² < 0.08) and between 10 nm and 13 nm in n-hexane (μ₂/Γ² < 0.09), respectively.     

Amphiphilic diblock and ABC triblock methacrylate copolymers: synthesis and aqueous solution characterization

Three isomeric, linear, equimolar, amphiphilic ABC triblock copolymers comprising methyl methacrylate (MMA, nonionic hydrophobic), 2-(dimethylamino)ethyl methacrylate, (DMAEMA, ionizable hydrophilic) and hexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) units (10 units in each block) were synthesized by group transfer polymerization (GTP). These were the three block sequence isomers, ABC, ACB and BAC. The corresponding random terpolymer was also prepared. The molecular weights and compositions of all the polymers were characterized by GPC and ¹H NMR. Measurements of the hydrodynamic diameters and cloud points of the copolymers in aqueous solution suggest that the various distributions of monomer units in the four terpolymers (the three triblocks and the random) result in different supramolecular structures with different colloidal stabilities.     

Synthesis of pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] copolymer and gold nanoparticle stabilization by its micelles

Novel pH‐ and temperature‐responsive chitosan‐graft‐poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (chitosan‐g‐PDMAEMA) copolymers were successfully synthesized by homogeneous atom transfer radical polymerization (ATRP) under mild conditions. Chitosan macroinitiator was prepared by phthaloylation of amino groups of chitosan and subsequent acylation of hydroxyl groups of chitosan with 2‐bromoisobutyryl bromide. The copolymers were obtained by ATRP of 2‐(N,N‐dimethylamino)ethyl methacrylate and they can self‐assemble into stable micelles in water. Hybrid micelles with a PDMAEMA corona incorporating gold nanoparticles (Au NPs) were prepared in situ via the reduction of HAuCl₄ with NaBH₄. The pH and temperature responses of the copolymer micelles and hybrid micelles were characterized using UV‐visible spectroscopy and dynamic laser light scattering. The morphology of the micelles was observed using transmission electron microscopy and atomic force microscopy. The PDMAEMA corona of the micelles acts as the ‘nanoreactor’ and the ‘anchor’ for the in situ formation and stabilization of Au NPs. Therefore, the spatial distribution of Au NPs within the micelles can be tuned by varying the temperature and pH value. Copyright © 2010 Society of Chemical Industry