Regulating Block Copolymer Assembly Structures in Emulsion

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Interface Components: Nanoparticles, Colloids, Emulsions, Surfactants, Proteins, Polymers

Regulating Block Copolymer Assembly Structures in Emulsion Droplets through Metal Ions Coordination Yuqing Wu, Haiying Tan, Yi Yang, Yuce Li, Jiangping Xu, Lixiong Zhang, and Jintao Zhu Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.8b02135 • Publication Date (Web): 28 Aug 2018 Downloaded from http://pubs.acs.org on September 2, 2018

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Regulating Block Copolymer Assembly Structures in Emulsion Droplets through Metal Ions Coordination Yuqing Wu,† Haiying Tan,† Yi Yang,† Yuce Li,† Jiangping Xu,†, ‡, * Lixiong Zhang,§ Jintao Zhu†, ‡, * †

Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education,

School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China ‡

State Key Laboratory of Materials Processing and Mold Technology, HUST, Wuhan 430074, China

§

State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University,

Nanjing 210009, China *Corresponding authors, E-mail: [email protected] (J. X.), [email protected] (J. Z.)

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Abstract. In this report, we demonstrate the metal ions coordination induced morphological transition of block copolymer

(BCP)

assemblies

under

three-dimensional

(3D)

confinement.

Polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) aggregates with various morphologies can be obtained by emulsion solvent-evaporation in the presence of metal ions (e.g., Pb(II) and Fe(III) ions) in the aqueous phase. Due to the coordination interaction between 4VP units and metal ions, the overall shape, internal structure and surface composition of the particles can be tailored by varying type and concentration of the metal ions. For example, when Pb(II) ions were employed, morphological transition of the assemblies occurred due to the formation of P4VP-Pb(II) complexes. More interestingly, when Fe(III) ions were added, hydrolysis of Fe(III) caused the reduction of the pH value of the aqueous phase, leading to the protonation of 4VP units. As a result, interfacial instability took place to trigger the splitting of emulsion droplets and then formation of nano-sized micelles. Therefore, metal ions coordination is a facile strategy to tune the structure of assemblies under 3D confinement, and offers an alternative approach for the design of organic-inorganic hybrid assemblies with well-tunable structures. Keywords: Block copolymers; Self-assembly; Emulsions; Interfacial instabilities; Metal ions coordination; Confinement

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INTRODUCTION Structured block copolymer (BCP) particles have received considerable attention since shape and internal structures of the particles play critical roles in their properties, including targeting delivery ability,1 cellular uptake behavior,2 rheological property,3, 4 self-assembly behavior,5 catalysis efficiency,6 and others. Therefore, how to systemically control morphology of the polymer particles is of great importance. Responsive polymeric materials can undergo morphological changes upon external stimuli (e.g., pH, temperature, solvent, light and ions).1, 2, 7-16 Moreover, additives (e.g., small molecules,17-19 metal ions,20 and homopolymers21-23) can also trigger the morphological transition of BCP particles, offering new opportunities to tune structures of assemblies. There have been examples of changing structure of BCP particles (or films) by adding ions.24-26 For instance, Eisenberg and coworkers reported that addition of ions (H+, OH-, and salts) had significant influences on the morphologies of BCP micelles in selective solvents.27,

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Kim and coworkers

fabricated porous thin films using BCP micelles loaded with metal ions.29 Recently, Hawker et al. studied the controllable self-assembly of amphiphiles via metal ion coordination. Isolated micelles, aggregated particles, and multi-lamellar vesicles could be obtained by introducing different divalent transition metal ions.20 Three-dimensional (3D) confined assembly is a powerful tool to break the symmetry of a structure, thus allowing materials to form structures that are not accessible in bulk or solution state.30 Emulsion-solvent evaporation has been employed as a simple strategy to realize 3D confinement of BCPs.31-42 Typically, BCPs are first dissolved in a water-immiscible organic solvent, which is then emulsified with surfactant aqueous solution to obtain emulsion droplets. After removal of the organic solvent by evaporation, nanostructured particles generated, which can be used as templates for 3


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constructing inorganic-organic hybrid nanomaterials.43, 44 Specifically, polystyrene-block-poly(vinyl pyridine) (PS-b-PVP) BCP has been widely studied since nitrogen atoms in the PVP block have unpaired electrons which can interact strongly with metal precursor and proton.25, 45 For example, PS-b-PVP microparticles obtained by 3D confined assembly were used as templates to generate BCP/gold nanoparticle (NPs) composites (a two-step strategy).46 Alternatively, there is a one-step method to engineer the overall shape, internal structure, and interfacial composition of the polymeric assemblies by introducing metal ions in aqueous phase, in which the metal precursors are added before the formation of BCP particles. In this case, the additives (metal ions) would change the interaction among polymer blocks and also the oil/aqueous interfacial interaction, and thus modify the self-assembly behavior of BCP under confinement. Yet, to the best of our knowledge, how the addition of metal ions affects the interfacial interaction and morphology of the BCP assemblies under 3D confinement is not clear until now.

Scheme 1. Illustration showing the 3D confined assembly of PS-b-P4VP in the presence of metal ions. Red color represents PVA. Blue and cyan colors indicate P4VP and PS domains, respectively (the same in the following figures). The emulsion droplets were obtained by emulsifying chloroform solution containing PS-b-P4VP (10 mg/mL) and PVA aqueous solution (3 mg/mL) containing metal ions.

Here, we report the manipulation of morphology of PS-b-P4VP assemblies under 3D confinement (Scheme 1) through metal ions (e.g., Pb(II) and Fe(III)) coordination. Both Pb(II) and 4


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Fe(III) ions not only significantly vary the interfacial behavior of the emulsion droplets, but also affect the self-assembly of BCPs in emulsion droplets. Therefore, the morphology of BCP assemblies can be well tailored by varying ion type and concentration.

EXPERIMENTAL SECTION Materials: All the diblock copolymers, PS9.8K-b-P4VP10K (the subscripts are the Mn of the blocks, Mw/Mn = 1.08), PS17K-b-P4VP49K (Mw/Mn = 1.05), and PS51K-b-P4VP18K (Mw/Mn = 1.15) were purchased from Polymer Source, Inc., Canada. The surfactant, poly(vinyl alcohol) (PVA, average Mw: 13K−23K g/mol, 87−89% hydrolyzed), was purchased from Sigma-Aldrich. NaCl, PbCl2, and FeCl3 were purchased from Sinopharm Chemical Reagent. All of the materials were used as received without further purification. Preparation of the BCP assemblies: Emulsion-solvent evaporation method was employed to prepare BCP assemblies. Typically, PS-b-P4VP was dissolved in chloroform (10 mg/mL). Subsequently, 0.1 mL of the BCP solution was emulsified with 1.0 mL of PVA aqueous solution (3 mg/mL) containing different concentrations of metal ions by membrane-extrusion emulsification or hand shaking vigorously. Then, the emulsions were collected in a 10 mL open vial to allow slow evaporation of chloroform for 24 h at 30 °C. Then, the samples were washed with deionized water (DI water) to remove PVA and unreacted ions by repeated centrifugation for three times (16,000 rpm for 8 min) and redispersed in DI water under sonication for further characterization. Characterization: Internal structures of the BCP assemblies were investigated using FEI Tecnai G2 20 transmission electron microscope (TEM) operated at an acceleration voltage of 200 kV. Before TEM characterization, the samples were selectively stained with iodine vapor for 2 h at 30 °C (for P4VP block). Scanning electron microscopy (SEM) images were collected by JEOL S-4800 SEM 5


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operated at an acceleration voltage of 20 kV. The Fourier transform infrared spectroscopy (FT-IR) (Equinox 55, Bruker) and XPS (X-ray photoelectron spectroscopy) (VG ESCALAB 250 spectrometer with an Al Kα X-ray source (1486 eV), X-ray radiation (15 kV and 10 mA)) were used to characterize coordination interaction between the pyridine group and metal ions. The evaporation of emulsion droplets was monitored by an inverted optical microscope (Olympus IX71) on bright-field optical mode. The pH value of aqueous phase was measured with a Mettler-Toledo pH meter (FE20). To measure the water contact angle, BCP solutions were spin-coated on glass substrates and dried at 45 °C to form uniform films. Then, a drop of water with varied concentration of ions was dropped on the substrate. The water contact angles were measured and captured on an optical contact-angle measuring device (JC2000C1, Dataphysics Instruments Shanghai Zhongchen Digital Technic Apparatus co., Ltd). The pendent drop method was selected for measuring the surface and interfacial tensions.47 The surface tensions of the organic liquids were determined from pendent drops formed within closed cells. To measure the interfacial tension (γ) as a function of concentration of ions (CMn+), a vertically placed syringe with BCP solution (10 mg/mL) was immersed in PVA aqueous solution (3 mg/mL) with varied CMn+. Then, a drop BCP solution was slowly injected into the aqueous phase. When the droplet of BCP reached equilibrium state (close to drop down), size of the droplet was recorded through the measuring device (JC2000C1) for calculation of the interfacial tension.

RESULTS AND DISCUSSION Effects of Pb(II) Ions Concentration on the Morphology of PS-b-P4VP particles PS-b-P4VP particles were prepared by the emulsion-solvent evaporation method. As organic solvent 6


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evaporates, the emulsion droplets shrink, eventually leading to the formation of BCP particles and the microphase separation of BCPs within the confined spaces. After complete removal of the organic solvent, PS9.8k-b-P4VP10k self-assemble into ellipsoidal pupa-like particles with PS and P4VP lamellar domains alternatively stacked (Figure 1a), owing to the comparable interfacial interactions of the PS and P4VP block with PVA aqueous solution.31, 48, 49

Figure 1. TEM images and corresponding schematic illustrations (upper-right insets) of the PS9.8k-b-P4VP10k-Pb(II) particles obtained by solvent evaporation of emulsions containing PS9.8k-b-P4VP10k in chloroform phase (10 mg/mL) and Pb(II) ions with varied concentration: (a) 0 M; (b) 0.001 M; (c) 0.04 M; (d) 0.1 M, in PVA aqueous solution (3 mg/mL). After staining with iodine vapor, the P4VP domains become black while the PS domains appear gray.

Due to the unpaired electrons on nitrogen, the 4VP unit can efficiently bind to metal ions with empty valence orbitals.25, 26, 50, 51 We thus investigated the effects of Pb(II) ions, which can coordinate with 4VP units, on the morphology of PS-b-P4VP particles. The pupa-like particles of PS9.8k-b-P4VP10k are still found (Figure 1b) when the concentration of Pb(II) is extremely low (CPb(II) = 0.001 M, pH= 5.45). However, as CPb(II) increases to 0.04 M (pH = 4.65), the original discoid-like P4VP domains (Figure 1a and 1b) transform to bent lamellar domains (Figure 1c). Further increasing

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CPb(II) to 0.1 M (pH= 4.37), particles with spherical P4VP-Pb(II) domains were observed (Figure 1d). The lamella-to-sphere transition can be attributed to the reduction of the geometric packing parameter of P4VP chains arising from the coordination effect which makes P4VP block crosslink and thus shrink. The shrinkage of P4VP domains becomes more remarkable as CPb(II) increases, resulting in the structural transition of P4VP domains. Additionally, the outermost layer of these particles is occupied by P4VP-Pb(II), which is proved by selectively loading gold NPs in P4VP domains (Figure S1a-b in the Supporting Information (SI)). Due to the formation of P4VP-Pb(II) complexes, which have higher affinity to water,52 the oil/water interfaces become selective for P4VP-Pb(II) complexes. As a result, the outermost layer changes to P4VP-Pb(II) domains as the increase of CPb(II). As a comparison, when Na(I) ions, instead of Pb(II) ions, were added, the pupa-like structure of PS9.8k-b-P4VP10k did not change obviously, even when the CNa(I) was as high as 0.1 M (Figure S2a). Owing to pH(Na(I)) (=5.6) > pKa(P4VP) (=4.8) and the labile P4VP-Na(I) complexes,53, 54 the addition of Na(I) ions neither obviously affect the interfacial behavior of the droplets nor morphologies of the BCP particles. This result confirms that the coordination effect between 4VP units and metal ions plays an important role in morphological transition. We then characterized the status of Pb(II) in the particles. Energy dispersive X-ray spectroscopy (EDS) measurements (Figure 2a) confirmed the presence of Pb in the particles. XPS spectra show that an original peak of N(1s) is at ~ 399 eV (Figure 2b, black line), which can be attributed to the N-C bond. A new peak appears at 407.5 eV after the introduction of Pb(II) ions (Figure 2b, red line), which represents the N-Pb(II) bond. Fourier-transform IR (FT-IR) was employed to confirm the interaction between 4VP unit and Pb(II). In the presence of 0.1 M Pb(II) ions, the original 8


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characteristic peaks at 1595 cm−1 (νC=C+C=N) and 1413 cm-1 (νC−N) of the pyridine ring shift to higher frequencies upon complexation with Pb(II) (Figure S3). This shift indicates the formation of coordinative bonds between N atom and Pb(II). Furthermore, a new absorption peak appeared at 1636 cm−1, indicating the interaction of P4VP unit and Pb(II).55-57

Figure 2. (a) EDS spectrum of the sample in Figure 1d. (b) X-ray photoelectron spectroscopy (XPS) spectra of PS9.8k-b-P4VP10k particles (black line) and PS9.8k-b-P4VP10k particles containing Pb(II) ions (red line).

To test the generality of this strategy, we then applied the coordination strategy to asymmetric PS17k-b-P4VP49k. Similar morphological transition to that of PS9.8k-b-P4VP10k particles could be found when CPb(II) increased to 0.06 M (Figure 3b-c). Bud-like particles were formed at CPb(II) = 0.06 M. Both the PS (Figure S4a) and P4VP blocks (Figure S4b) located on the oil/water interface, which was confirmed by selectively loading of gold NPs (Figure S4). We note that, when CPb(II) increased to 9


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0.1 M, particles with rough surface can be obtained (Figure 3d). The reason can be ascribed to the enhanced affinity of P4VP-Pb(II) complex to PVA since the P4VP block becomes longer for PS17k-b-P4VP49k. Therefore, the polymer chains spontaneously increase the surface area by migrating to the oil/water interface. We also applied this strategy to asymmetric PS51k-b-P4VP18k with shorter P4VP chains (compared to PS chains), and found that morphologies of the P4VP domains in PS51k-b-P4VP18k assemblies does not change obviously as the increase of CPb(II) (Figure S5a-c). Since the P4VP is short, variation of geometric packing parameter of P4VP chains arising from the coordination effect is not strong enough to induce the morphological transition. Additionally, the interfacial tension of the emulsion droplets with different BCPs at varied CPb(II) were measured (Figure S5d). Initial interfacial tension is measured to be ~ 6 mN/m. When CPb(II) = 0.1 M, interfacial tension of PS51k-b-P4VP18k and PS9.8k-b-P4VP10k decreases to ~ 3 mN/m, while that of PS17k-b-P4VP49k decreases to ~ 2 mN/m because of the longer P4VP chains. The reduced interfacial tension of oil/water will induce the increase of interfacial area of the emulsion droplets, which can be used to explain the formation of PS17k-b-P4VP49k particles with rough surface. In a control experiment, we found that Na(I) ions do not have obvious effect on the morphology of PS17k-b-P4VP49k assemblies (Figure S2b). The above results indicate that Pb(II) ions play at least two important roles in the morphological transition of PS-b-P4VP assembles: 1) varying the interfacial selectivity by increasing the affinity of PVA to P4VP block, and 2) shrinking the P4VP domains by crosslinking.

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Figure 3. TEM images of the PS17k-b-P4VP49k-Pb(II) particles obtained by solvent evaporation of emulsions containing PS17k-b-P4VP49 in chloroform phase (10 mg/mL) and Pb(II) ions with varied concentration: (a) 0 M; (b) 0.001 M; (c) 0.06 M; (d) 0.1 M, in PVA aqueous solution (3 mg/mL). After staining with iodine vapor, the P4VP domains become black while the PS domains appear gray. The upper-right inset of (d) shows a representative SEM image of the particle with rough surface while upper-right inset in (a) and (b) are the cartoons showing the pupa-like particles.

Interfacial Instabilities of Emulsion Droplets Triggered by Fe(III) Ions We then investigated the structural transformation of PS9.8k-b-P4VP10k assemblies induced by Fe(III) ions, which can coordinate with 4VP unit and hydrolyze in water to decrease pH value of the solution.58 At very low concentration of Fe(III) ions (CFe(III) = 0.001 M, pH = 3.0), the structure of assembles changes from pupa-like particle (Figure 1a) to onion-like structure with P4VP as the outermost layer (Figure 4a). Further increasing CFe(III) to 0.1 M (pH = 1.8), interfacial instability of the emulsion was observed as the evaporation of organic solvent. The large droplets break up into smaller ones and release the BCPs into the aqueous phase (Figure 5), leading to the formation of nano-sized vesicles (Figure 4b). In the presence of Fe(III) ions, the pH value of the aqueous solution

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decreases dramatically due to the hydrolysis of Fe(III). When pH < pKa(P4VP), the pH-sensitive P4VP blocks are protonated, leading to the structural transition of the assemblies. When CFe(III) = 0.001 M, the partially protonated P4VP chains become hydrophilic, which prefer to locate at the oil/water interface, resulting in the onion-like particles. When CFe(III) = 0.1 M, the lower pH value enables the increase of degree of protonation. Therefore, the P4VP blocks become more hydrophilic, which significantly decreases the interfacial tension and triggers the interfacial instability of the droplets.59 In our previous work, we found that mixture of vesicles and cylindrical micelles could be obtained at pH = 1.8 without metal ions in the aqueous solution.49 However, as shown in Figure 4b, the presence of Fe(III) leads to exclusive formation of vesicles. One possible reason is the coordination between P4VP and Fe(III) ions results in the decrease of repulsion interaction among P4VP corona chains, which suppresses the formation of cylindrical micelles. This difference clearly indicates that both the hydrolysis and coordinate interaction affect the structure of BCP assemblies. To elucidate the role of the CFe(III) in the assembly of BCPs, the interfacial tension of the droplet was measured through pendant drop tensiometry as a function of CFe(III) (Figure 4c). The interfacial tension decreases dramatically as the increase of CFe(III). Even at extremely low CFe(III) (0.001 M), the interfacial tension significantly decreases to ~ 0.2 mN/m. Presumably, this is ascribed to the absorption of protonated BCPs at the oil/water interface. The interfacial tension would decrease further and approach to zero when more protonated BCPs migrate to the interface during solvent evaporation, triggering interfacial instability of the droplets. As a comparison, Figure 4c also shows that the presence of Pb(II) reduces the interfacial tension slightly from 6.0 to 3.0, which is not enough to cause the interfacial instability. This also confirms the above TEM results for PS9.8k-b-P4VP10k-Pb(II) system (Figure 1b-d). 12


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Figure 4. (a, b) TEM images of the PS9.8k-b-P4VP10k-Fe(III) assemblies obtained by solvent evaporation of emulsions containing PS9.8k-b-P4VP10k in chloroform phase (10 mg/mL) and Fe(III) with varied concentration: (a) 0.001 M, (b) 0.1 M, in PVA aqueous solution (3 mg/mL); (c) Plot of the interfacial tension of the emulsion droplets containing PS9.8k-b-P4VP10k at varied CFe(III) and CPb(II). The interfacial tension for chloroform/PVA aqueous solution was measured through pendant drop tensiometry.

Moreover, we measured the contact angles between water containing different CFe(III) and PS9.8k-b-P4VP10k films to indicate the hydrophobic-hydrophilic transition. The initial contact angle between pure water and PS9.8k-b-P4VP10k is 88º (Figure S6a). When CFe(III) = 0.001 M, the contact angle decreases to 67º (Figure S6b). As the increase of CFe(III) to 0.1 M, the contact angle reduces to 30.5º (Figure S6d). FT-IR spectroscopy is then used to characterize the interaction between 4VP units and proton (Figure S7). The original characteristic peaks associated with pyridine rings, 1595 cm-1 and 1413 cm-1 shift to higher frequencies. A new characteristic peak appears at 1637 cm-1 due to the N−H bending vibration, indicating the formation of ionized 4VP units.19, 45, 49

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Figure 5. Optical microscopy images showing the evolution of the emulsion droplet during organic solvent evaporation. The droplets are obtained by emulsification of PS9.8k-b-P4VP10k in chloroform phase (10 mg/mL) and 0.1 M Fe(III) in PVA aqueous solution (3 mg/mL). The scale bar in (a) applies to (b-d) as well.

We also studied the influence of architecture of BCPs on the assemble behavior. Asymmetric BCPs with similar molecular weight while different block ratios, i.e., PS17k-b-P4VP49k (weight fraction of P4VP, wP4VP = 0.74) and PS51k-b-P4VP18k (wP4VP = 0.26), form different aggregates. When CFe(III) = 0.001 M (pH = 3.0), the P4VP blocks were not fully ionized. The PS17k-b-P4VP49k forms onion-like particles (Figure 6a) while the structure of PS51k-b-P4VP18k particle does not change obviously (Figure 6d). When increasing the CFe(III) to 0.005 M (pH = 2.56), PS51k-b-P4VP18k assembles into particles with rough surface (Figure 6e). The enhanced hydrophilicity of P4VP induced the interfacial instability, resulting in the increase of interfacial area. However, the hydrophilicity in this case was not strong enough to induce the breakage of emulsion droplets. In contrast, PS17k-b-P4VP49k with longer P4VP blocks has stronger hydrophilicity, resulting in the breakage of the emulsion droplets and the formation of spherical micelles (Figure 6b). Further increasing the CFe(III) to 0.1 M (pH = 1.8), the P4VP blocks were fully ionized. Thus, the hydrophilicity of P4VP chains was dramatically enhanced. As a result, the droplets broke to induce the formation of nano-sized assemblies. For example, PS17k-b-P4VP49k forms spherical micelles (Figure 6c) while PS51k-b-P4VP18k assembles into large compound vesicles (LCVs) (Figure 6f). In this case, the repulsion among coronal chains influences in the micellar morphology. PS9.8k-b-P4VP10k forms exclusive vesicles. PS17k-b-P4VP49k with longer hydrophilic block and short 14


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hydrophobic PS chains forms spherical micelles; while PS51k-b-P4VP18k with shorter hydrophilic block and longer hydrophobic PS chains forms LCVs. The structure transition can be attributed to: 1) the hydrophobic-hydrophilic transition caused by partially protonation, and 2) the coordination between 4VP units and Fe(III) ions. Once the P4VP chains become hydrophilic, they are soluble in water and form the corona of the micelles.

Figure 6 TEM iamges of (a-c) PS17k-b-P4VP49k-Fe(III) and (d-f) PS51k-b-P4VP18k-Fe(III) aggregates obtained throough solvent evaporation of emulsions containing 10 mg/mL PS-b-P4VP s in chloroform phase and Fe(III) with varied concentration in aqueous phase: (a and d) 0.001 M, (b and e) 0.005 M, (c and f) 0.1 M. The inset in (f) is the representative SEM image of the particles.

CONCLUSIONS In summary, we have demonstrated the use of metal ions as a facile route to control the morphology of BCP assemblies. The coordinate interaction makes it possible to engineer the morphology of the aggregates. Both micro-particles and nano-micelles with different morphologies were generated through 3D confined assembly of PS-b-P4VP. The P4VP-Pb(II) coordination not only shrinks the 15


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P4VP domain, but also slightly changes the interfacial selectivity. As the increase of the CPb(II), P4VP domain of PS9.8k-b-P4VP10k changes from lamellar to bent lamellar, and then to spherical domains. While the addition of Fe(III) ions decreases the pH value of the solution, resulting in the hydrophobic-hydrophilic transition of P4VP blocks. In this case, the interfacial instability of the emulsion droplets will be triggered, leading to the formation of nano-sized assemblies. Therefore, the introduction of metal ions in aqueous phase has great influence in the self-assembly of BCPs and the interfacial behavior of the emulsion droplets. This strategy extends potentials to control the shape and complexity of BCPs assemblies.

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ASSOCIATED CONTENT Supporting Information Available: Additional TEM images and FT-IR spectra, contact angle measurement, and a supporting movie showing the interfacial instabilities of the emulsion droplets. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (J. X.) *E-mail: [email protected] (J. Z.) Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS We gratefully acknowledge funding for this work provided by National Natural Science Foundation of China (51473059 and 51525302), Natural Science Foundation of Hubei Scientific Committee (2016CFA001) and Open project of State Key Lab of Materials-Oriented Chemical Engineering (KL 16-04). We thank the HUST Analytical and Testing Center for allowing us to use its facilities.

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Table of content Entry: Title: Regulating Block Copolymer Assembly Structures in Emulsion Droplets through Metal Ions Coordination Authors: Yuqing Wu, Haiying Tan, Yi Yang, Yuce Li, Jiangping Xu, Lixiong Zhang, Jintao Zhu Graphic Abstract:

With the addition of transition metal ions to emulsion droplets containing block copolymers, overall shape, internal structure, and surface composition of the formed polymer particles can be tailored through the metal ion coordination with one of the blocks.

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Regulating Block Copolymer Assembly Structures in Emulsion

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