Versatile Tri-Block Janus Nanoparticles: Synthesis and Self-Assembly

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Versatile Tri-Block Janus Nanoparticles: Synthesis and Self-Assembly Chengjun Kang, and Andrei Honciuc Chem. Mater., Just Accepted Manuscript • Publication Date (Web): 12 Feb 2019 Downloaded from http://pubs.acs.org on February 12, 2019

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Chemistry of Materials

Versatile Tri-Block Janus Nanoparticles: Synthesis and Self-Assembly Chengjun Kang†, Andrei Honciuc†*

†Institute

of Chemistry and Biotechnology, Zurich University of Applied Sciences,

Einsiedlerstrasse 31, 8820 Waedenswil, Switzerland.

ABSTRACT: Multi-block Janus nanoparticles (JNPs) are anisotropic particles composed of different blocks/lobes with distinct physico-chemical properties. The ultimate goal is to obtain JNPs that carry two or more contrasting bulk and surface properties on different parts of the same particle. JNPs are promising candidates for various applications, such as building-blocks for self-assembly and multi-functional materials. Here, we report the chemical synthesis of a special type of “versatile” tri-block JNPs, which contains three lobes with different chemical compositions, whereby “versatile” means that the tri-block JNPs can be separately and independently modified on at least two different lobes

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through different chemical reactions, offering limitless design possibilities. We further prove that specific chemical tailoring determines the way the JNPs interact and selfassemble, such that either normal or reverse micelles are obtained. In particular, the formation of micelles from tri-block JNPs constitutes an initial example of the classical concepts extension from tri-block polymers to colloids. We regard the tri-block JNPs as representatives of a broader class of versatile anisotropic colloids, giving the ability to combine various functionalities on different parts of the same particle, thus enriching the tool box of nanomaterials and broadening their application potential.

INTRODUCTION

Janus nanoparticles (JNPs) with anisotropic geometries are interesting because they could carry two or more different bulk and/or surface properties on different parts of the same particle.1 It’s evident that the nature of these “loaded” properties plays a key role in JNPs’ application. For example, Janus colloids carrying different chemical compositions on different parts of the same particle, resembling different covalent bonds or functional groups in an individual small molecule, have been frequently used as an


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excellent model to study diffusion limited chemical reactions2 and polymerizations3–5 that are difficult to be directly observed in molecular world. Furthermore, compared to colloids with homogeneous chemistry, JNPs proved superior in applications, such as ultra-stable Pickering emulsions,6 emulsions phase switching,7 self-propelled nanomotors,8–10 controlled self-assembly11 and self-assembly into various suprastructures,12– 17

coupling surface and bulk properties,18 etc.

The significance in both scientific understanding and practical applications stimulated a concerted effort for designing a whole variety of JNPs.19–23 The central idea is to “load” an arbitrary combination of contrasting properties on different parts of the same JNPs; this requirement can be partially satisfied by several synthetic approaches, with their own advantages and disadvantages. For example, capillary force can be used to combine different spherical particles together to prepare asymmetric JNPs.24–27 However, the different parts of the JNPs held together by physical forces can easily disintegrate upon further processing. Besides, very limited number of JNPs can be produced by this method and is thus limited for practical applications. Seeded emulsion


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polymerization (SEP) is the most frequently used method to prepare sturdy polymeric JNPs,28–30 with the clear advantage of scalability and simplicity. The disadvantage is that the generated Janus lobes are difficult to further functionalize. This shortcoming could be overcome by introducing “versatility” into the JNPs. By versatility we mean that two or more different parts of the same anisotropic JNPs can be independently and selectively functionalized, such that any contrasting properties can be combined into the same JNPs. Previously, two-lobe JNPs with one “clickable” lobe has been proposed,31 as a step forward to improve the chemical versatility of JNPs, but the other lobe cannot be further modified. An extension of two-lobe JNPs into a three-lobe or tri-block JNPs with two chemically modifiable lobes could carry more different properties on the same particle and thus be more “versatile”. However, the chemical synthesis of three-lobe JNPs with different chemistries is much more challenging than that of the two-lobe JNPs, which is probably the reason why their properties, such as self-assembly and formation of suprastructures, was much less studied.


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In the present study, we report the synthesis of a special type of JNPs, which contains three different lobes/blocks, which inherit the ability to self-assemble from the two-lobe JNPs precursor. Further, we demonstrate the versatility of these tri-block JNPs by modifying selectively and independently the chemistry of two different lobes. Chemical tailoring is crucial because it determines the way the JNPs interact and self-assemble; we show that by combining specific chemical composition with specific physical geometries, snowman JNPs can be made to self-assemble into normal or “reversed” micelles.

RESULTS AND DISCUSSION

Siloxane derivative (3-(triethoxysilyl)propyl-methacrylate) (TPM) has been frequently used for the fabrication of JNPs, because it can attach on various nanoparticles’ (NPs) surfaces and the subsequent phase separation leads to the formation of JNPs during SEP.18 However, the obvious disadvantage is that this monomer has no functional groups and further chemical modification on the resulted JNPs is difficult to perform. For


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constructing versatile JNPs, we hypothesize that other siloxane derivatives carrying functional groups may also be able to form JNPs. Following this thought, we used 3(trimethoxysilyl)propane-1-thiol (TMPT) monomer with a chemically versatile thiol group, which showed the ability to form JNPs by SEP. Because poly(tert-butyl acrylate) (PtBA) NPs can be functionalized by the hydrolysis of tert-butyl groups under mild conditions,32 we choose PtBA as the seed NPs. The synthesis of snowman-shaped PtBA-PTMPT JNPs is shown in Figure 1a, with a zeta potential of -54.6 ± 0.9 mV. Next, thiol-ene click reaction was used to selectively modify the PTMPT lobe of PtBA-PTMPT JNPs.33 To test the “clickable” property, poly(ethylene glycol) methacrylate (PEG-MA, 300g/mol) was selected as an example to selectively modify PtBA-PTMPT JNPs (Figure S1). PEG-MA was selected because of its low glass transition temperature with liquid-like property at room temperature, which facilitate the observation of click reaction result. From SEM images (Figure S1d,e) we can see that the PTMPT lobe was “liquefied” after the click reaction, which implies considerable amount of PEG molecules attached on the PTMPT lobe, while the PtBA lobe remained unchanged. The PEG adsorption peak


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(1099 cm-1) on the JNPs FTIR spectrum further confirmed the successful thiol-ene click reaction (Figure S1f).

Figure 1. Synthesis and self-assembly of PtBA-PTMPT JNPs. (a) Scheme showing the synthesis of PtBA-PTPTM JNPs with different PTPTM lobe sizes. (b) PtBA-PTPTM JNPs with the TPTM lobe formed by 0.8 ml monomer. (c-f) Micelles generated by the


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self-assembly of JNPs depicted in (b). (g) PtBA-PTPTM JNPs with the PTPTM lobe formed by 2.0 ml monomer. (h-k) Micelles generated by the self-assembly of JNPs depicted in (g).

In addition to the selective chemical modification on the PTMPT lobes, PtBA-PTMPT JNPs showed unexpected self-assembly behavior. We noticed that when the PTMPT lobe (242 ± 4 nm) is slightly smaller than the PtBA lobe (251 ± 5 nm), these PtBAPTMPT JNPs automatically self-assembly into suprastructures in aqueous solution without any external stimuli. Most of the self-assembled structures are spherical- and worm-like micelles containing four to tens of individual PtBA-PTMPT JNPs (Figure 1, Figure S2). Individual JNPs orient in such a way that the PTMPT lobes come in contact with each other, while the PtBA lobe point toward the aqueous solution; additionally, we hypothesize that these self-assembled structures are stabilized in aqueous solution by the negative charges on the PtBA lobe surface. An overview of the assembled structures can be seen in Figure S2a. The driving force for the assembly of PtBAPTMPT JNPs is not very well understood at this point, but we are certain that the PtBA-


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TMPT JNPs self-assembly relies on the chemistry of the PTMPT lobe, this is because as we change the PTMPT lobe into the PTPM lobe with the same geometry, the PtBAPTMP JNPs do not show any sign of self-assembly under identical experimental conditions (Figure S2b). On one hand, as we increase the size of the PTMPT lobe from 242 ± 4 nm to 331 ± 6 nm by controlling the feed ratios between the PtBA seed NPs and TMPT monomer, we cannot observe the formation of any suprastructures consisting of highly oriented JNPs. This observation confirms the importance of JNPs physical morphologies in selfassembly.15 On the other hand, as we previously demonstrated the attractions between the PtBA lobes can make PtBA-PTPM JNPs JNPs self-assembly into various suprastructures when the PTPM lobe is larger than the PtBA lobe.17 In the present study, similarities can be found between the PtBA-PTPM JNPs and PtBA-PTMPT JNPs, and when the PTMPT lobe size larger than the PtBA lobe, PtBA-PTMPT JNPs can realize assembly by employing the hydrophobic attraction between the PtBA lobes (Figure 1gk). The PtBA-PTMPT JNPs self-assembled suprastructure contains 4 to tens of individual JNPs, each orients in such a way that the PtBA lobes closely contact with


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each other, while the PTMPT lobes pointing toward aqueous solution; this JNPs orientation manner is completely reversed as compared to the self-assembly of PtBAPTMPT JNPs with smaller PTMPT lobes. These above observations indicate two key factors responsible for the reversed JNPs orientation in self-assembled structures in monophasic medium. Firstly, the morphology of JNPs should be adjusted, such that the “curvature” of the JNPs is suitable for self-assembly in supra-structures in a reversed way, as explained shortly. Furthermore, the chemical structures of the two JNPs lobes should be carefully designed, because the reversed JNPs orientation requires each of the two lobes to perform as attraction or repulsion parts under specific conditions.


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Figure 2. Synthesis of tri-block JNPs. (a) Scheme showing the synthesizing of tri-block JNPs. (b, c) SEM images of PtBA-PTPM JNPs. (d, e) SEM images of PAA-PTPM JNPs. (f, g) SEM images of PAA-PTPM-TPTM tri-block JNPs. (h) FTIR spectra of PtBA-PTPM (), PAA-PTPM (), PAA-PTPM-TMPT ().

Even though the PtBA-PTMPT JNPs can be modified on PTMPT lobe by thiol-ene click reaction, truly versatile Janus particles should be independently modified on


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minimum two parts of the same particle. We, therefore, continue to design and synthesis JNPs containing three lobes with different chemical compositions, namely triblock anisotropic JNPs. To achieve this goal, we added one more synthetic step into the PtBA-PTMPT JNPs synthesis procedure (Figure 2a). In the tri-block JNPs synthetic procedures, the PtBA-PTPM JNPs was synthesized in the first step, then the PtBA lobe was hydrolyzed in dichloromethane with ZnBr2 Lewis acid.32 The mild hydrolysis conditions will not affect the ester bond in the PTPM lobe, but only specifically remove

tert-butyl groups from the PtBA lobe. The successful hydrolysis of the PtBA lobe was confirmed by both SEM and FTIR characterization. From Figure 2b-e we can see that the diameter of the PtBA lobe decreased from 251 ± 5 nm to 223 ± 6 nm after hydrolysis. Additionally, the absorption peak of in FTIR spectra shift from 1725 cm-1 to 1710 cm-1 (Figure 2h), which confirms the formation of carboxyl groups and transfer the PtBA lobe into poly(acrylic acid) (PAA) lobe; the newly formed JNPs is noted as PAAPTPM. Under basic conditions (pH=9.0), the negative charges make the PAA lobe surface extremely hydrophilic, which is quite different from that of the PTMPT monomer, therefore, when we use the PAA-PTPM JNPs as the seed in SEP to grow the third


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PTMPT lobe, the TMPT monomer will not adsorb on the PAA surface but selectively attach on and phase separate from the PTPM lobe surface. SEM images (Figure 2f,g) demonstrate the successful fabrication of PAA-PTPM-PTMPT tri-block JNPs, from which we can see the attachment of the PTMPT lobe selectively on the PTPM lobe surface and the PAA lobe size remains unchanged. This procedure for the synthesis of tri-block JNPs showed good reproducibility and the obtained JNPs are uniformly distributed (Figure 2f,g). This tri-block JNPs do not have linear morphologies, the center of the third PTMPT lobe is not at the extrapolation line of the PAA lobe and PTPM lobe center, but instead at an angle around 15°. The tri-block JNPs fabrication process is further confirmed by FTIR spectrum (Figure 2h). The complete phase separation of the PAA-PTPM-PTMPT tri-block JNPs is confirmed by the following facts: firstly, from SEM images we could notice the different brightness of each lobe in the PAA-PTPM-PTMPT JNPs, specifically, the PAA lobe is the darkest, while the PTMPT lobe is the brightest (Figure 3). This brightness difference indicates these three lobes differ in their electron density, and thus they are different in their chemical composition, which implies the complete phase separation between these


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lobes. Furthermore, even though the PAA-PTPM-PTMPT JNPs are quite stable under ambient conditions, they can be separated into individual parts under strong mechanical shear force conditions. Figure 3 b shows the SEM images of the tri-block JNPs after ultrasonication in DMF for 15 min, from which we could clearly identify each parts of the tri-block JNPs. For example, we could observe PTPM-PTMPT (Figure 3d), PAA-PTPM (Figure 3e), PTMPT (Figure 3f), PTPM (Figure 3g) and PAA (Figure 3h) parts, respectively. The PAA part can easily be identified because of its spherical morphologies. Both the PTMPT and the PTPM parts have concave hemispherical geometry, we can distinguish them by their difference in diameter, the PTMPT (387 ± 7 nm) part is larger than the PTPM part (290 ± 9 nm). The possibility for the PAA-PTPMPTMPT tri-block JNPs to be mechanically separated into individual parts demonstrates the complete phase separation between each lobe.


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Figure 3. The complete phase separation of each part in the PAA-PTPM-PTMPT triblock JNPs. (a) Scheme showing the separation of each part in the PAA-PTPM-PTMPT JNPs, (i) represents ultrasonication procedure. (b) A large-field SEM image of tri-block JNPs after ultrasonication.

(c) SEM image of the PAA-PTPM-PTMPT JNPs before

sonication. (d-h) SEM images of the PTPM-PTMPT, PAA-PTPM, PTMPT, PTPM, PAA parts, respectively.

Before we present the self-assembly behavior of the PAA-PTPM-PTMPT tri-block JNPs, the self-assembly of the tri-block JNPs precursor, namely PAA-PTPM JNPs, is


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first discussed. As we have previously shown the PtBA-PTPM JNPs can self-assemble into various suprastructures in water/ethanol mixture under shearing conditions.17 Without the presence of shear force, the PtBA-PTPM JNPs cannot self-assemble suprastructures. This is because in water/ethanol mixture, electrostatic repulsion force prevents PtBA-PTPM JNPs approaching each other. Although the strength of electron repulsion force significantly reduced in organic solvents, such as in THF, the PtBAPTPM JNPs still cannot self-assemble into suprastructures; this phenomenon can be explained by the fact that PtBA-PTPM JNPs is completely solvated in THF, no attraction force exists to hold individual JNPs together for self-assembly. In contrast, as soon as PtBA-PTPM JNPs are hydrolyzed into the PAA-PTPM JNPs, we observed the selfassembly of the PAA-PTPM JNPs in THF without any shearing (Figure 4a,c-g). The self-assembled structures are mostly spherical or worm-like micelles, an overview of the self-assembled structures is shown in Figure S3. The PAA-PTPM JNPs orient in such a way that the PAA lobes contact with each other, while the PTPM lobes pointing toward solvent. Because of the stark difference between the PtBA-PTPM and PAA-PTPM JNPs in self-assembly, it is obvious that the PAA lobe is crucial for the self-assembly of the


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PAA-PTPM JNPs in THF. We think that the spontaneous assembly of the PAA-PTPM JNPs without mechanical energy input can be attributed to two factors: the first is that the electrostatic repulsion forces between JNPs are much weaker in THF as compared to that of in water, which facilitate JNPs approach each other. Secondly, because the presence of carboxyl groups on the PAA lobe, hydrogen bond can be the attractive force holding the PTPM JNPs together to realize self-assemblies. The above explanation can be verified in the following conditions, the PAA-PTPM JNPs should not self-assemble if either the electrostatic repulsion forces increases and/or the hydrogen bond between JNPs are destroyed. This is indeed the case, as the PAA-PTPM JNPs cannot form any self-assembly structures in basic aqueous solution (pH > 9.0). We considered to elucidate the self-assembly process by in situ observation with Dynamic Light Scattering (DLS), however, due to only a tiny number of self-assembled structures as compared to individual JNPs in self-assembly system, DLS or other techniques failed to distinguish the self-assembled structures from the mixture. We tried to decrease the interference of the individual nanoparticles by decreasing their diameter, but the smaller


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the nanoparticle we obtained, the wider the distribution of their size became, such that they are no longer good candidates for self-assembly.

Figure 4. Self-assembly of PAA-PTPM and PAA-PTPM-PTMPT JNPs. (a) Scheme showing the self-assembly of PAA-PTPM JNPs in THF. (b) Scheme showing the selfassembly of PAA-PTPM-PTMPT tri-block JNPs in THF. (c-g) SEM images of the selfassembled structures of PAA-PTPM JNPs. (h-l) SEM images of the self-assembled structures of the PAA-PTPM-PTMPT JNPs.


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The self-assembly of the PAA-PTPM JNPs indicates that the PAA lobe is the key factor to the realization of self-assembly. In the case of the PAA-PTPM-PTMPT JNPs, the PAA lobe was kept intact, which implies that the attraction between the PAA lobes could continue to act as the driving force to realize PAA-PTPM-PTMPT tri-block JNPs self-assembly. This hypothesis is verified by the fact that the PAA-PTPM-PTMPT triblock JNPs can self-assembly into suprastructures quite similar to that of the PAAPTPM JNPs. From Figure 4h-l we can see that the tri-block JNPs can self-assembly into suprastructures including spherical- and wormlike- micelles. Analogue to the PAAPTPM JNPs, the individual PAA-PTPM-PTMPT JNPs orient in such a way that the PAA lobes contact each other, while the PTMPT lobe is pointing toward solvent (a broader view can be found in Figure S3b). It seems that the third PTMPT lobe does not have significant influence on the self-assembly of JNPs. The relative amount of each type of self-assembled structures was characterized by the length distribution of the selfassembled structures (Figure S4), from which the spherical micelles are the most frequently self-assembled structures formed. It should be pointed out that the selfassembled suprastructures in the present study contain relatively small number of


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highly oriented JNPs, which may due to the fact that the suprastructures stop growing when their size reaches a certain limit before precipitation from solution, or because of the suprastrucures obtained in the present study is the largest stable structures in solution, any addition of JNPs of into these structures will make them too big to be stable in solution.

Figure 5. Influence of JNPs geometries on self-assembly. (a) Scheme showing the influence of PAA-PTPM JNPs geometries on the self-assembly of PAA-PTPM-PTMPT JNPs. (b) Scheme showing curvature angle of JNPs. (c-d) PAA-PTPM JNPs with the


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PTPM lobe smaller than the PAA lobe. (e-f) PAA-PTPM-PTMPT JNPs synthesized from (c).

Physical morphology is an important factor for colloidal self-assembly. As a preliminary study about the influences of geometry on the self-assembly of tri-block JNPs, we synthesized another PAA-PTPM JNPs with the PAA lobe larger than the PTPM lobe (Figure 5a,c,d), which demonstrates the good control of the relative lobe ratio of the seeded emulsion polymerization method. After the formation of the third PTMPT lobe, this newly synthesized tri-block JNPs has a middle PTPM lobe smaller than the other two lobes. As we previously reported,15 curvature angle (α) is a crucial parameter to determine the self-assembled structures of snowman shaped JNPs, the α is determined by the relative lobe size (Figure 5b). For snowman shaped JNPs, when the attractive lobe is smaller than the other lobe, α > 0, when two lobes have identical sizes, α =0, otherwise, α < 0. The larger the α is, the higher the possibility for snowman shaped JNPs to self-assembly into well-organized suprastructures. Conversely, when α has a negative value, it’s unlikely for JNPs to self-assemble into well-organized


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suprastructures. This conclusion is confirmed in the present study, we found that as for the PAA-PTPM JNPs, when the PAA lobe is smaller than the PTPM lobe, α > 0, suprastructures consists of well oriented JNPs obtained. As soon as the geometry of PAA-PTPM JNPs changes, such that the PAA lobe is bigger than the PTPM lobe, α < 0, no well-organized suprastructures can be obtained (Figure 5a). After the addition of the third PTMPT lobe (Figure 5e,f), those tri-block JNPs with PAA lobe larger than the PTPM lobe showed similar-assembly behavior to the PAA-PTPM JNPs, namely they cannot self-assemble into well-organized suprastructures. Based on these observations we conclude that the self-assembly behavior of the tri-block JNPs is largely influenced by their precursor snowman shaped JNPs. The comparison between the PAA-PTPM and the PAA-PTPM-PTMPT JNPs is meaningful, because it implies that the selfassembly behaviors of JNPs with two lobes might be able to extend to the selfassembly of JNPs with three lobes, as an inherited property.


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Figure 6. The “versatility” of PAA-PTPM-PTMPT tri-block JNPs. (a) Cartoon showing the selective modification of the PAA and PTMPT lobes. (b-c) SEM images of PAA-PTPMPTMPT tri-block JNPs after thiol-ene click reaction between the PTMPT lobe and NIPAM. (d-e) SEM images of PAA-PTPM-PTMPT tri-block JNPs after the esterification reaction between PAA lobe and NHS. (f) FTIR spectrum of PAA-PTPM-PTMPT tri-block JNPs before modification (), after the click reaction between the PTMPT lobe with NIPAM (), and after the esterification reaction between PAA lobe and NHS ().

Finally, we prove the chemical “versatility” of the PAA-PTPM-PTMPT tri-block JNPs. In the current work, the “versatility” of JNPs refers to such a property that at least two


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parts on the particles can be arbitrarily modified, therefore, different properties can be selected and “loaded” on different parts of a single particle. As a proof of concept, we demonstrate the selective modification on the PAA and the PTMPT lobes of the tri-block JNPs by different chemical reactions. First of all, as the PTMPT lobe carries thiol groups, thiol-ene click reaction is employed to modify the PTMPT lobe. We choose Nisopropylacrylamide (NIPAM) as an example to perform click reaction with JNPs,34 this is because NIPAM contains amide bond that can be easily identified after reaction. From Figure 6 we can see that after the thiol-ene click reaction, the size of PTMPT lobe increased from 387± 7 nm (Figure 2f,g) to 411 ± 9 nm (Figure 6b,c), while the size of the PAA lobe and the PTMP lobe remains constant. The appearance of adsorption peak at 1639 cm-1 in FTIR spectrum confirmed the attachment of the NIPAM onto JNPs (Figure 6f). In order to prove that NIPAM did not attach to the other parts of the tri-block JNPs, we expose PAA-PTPM JNPs to the same conditions as in the case of the above mentioned click reaction; we did not observe any attachment of the NIPAM onto the PAA-PTPM JNPs in the FTIR spectrum (Figure S5), which demonstrates NIPAM only attach to the PTMPT lobe of the PAA-PTPM-PTMPT tri-block JNPs. Then, because


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PAA lobe has carboxyl groups, the PAA lobe can be modified by esterification reaction. In the present study, we choose N-hydroxysuccinimide (NHS) as a representative example to demonstrate the reactivity of the PAA lobe, because the active ester formed by NHS can easily be transformed into other functional groups, and the active ester has a special adsorption peaks in FTIR, which can be easily recognized. After the esterification reaction, the size of the PAA lobe increased from 223± 6 nm (Figure 2f,g) to 255 ± 8 nm (Figure 6d,e), the new adsorption peak at 1738 cm-1, 1780 cm-1, 1810 cm-1 demonstrates the successful reaction between the PAA lobe and NHS (Figure 6f). In order to exclude the possibilities that NHS may attach to the PTPM and the PTMPT lobes, we exposed PtBA-PTPM and PtBA-PTMPT JNPs to the same reaction conditions in which the PAA-PTPM-PTMPT JNPs reacted with NHS. In this case we do not detect any attachment of NHS to these JNPs (Figure S5), therefore, we confirm that the NHS selectively attach only to the PAA lobe.

Conclusion


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The combination of different properties in different parts of a single particle is one of the most important advantages for Janus particles. In this work, we introduced a new siloxane derivative, namely TPTM, as monomer to synthesis JNPs. By controlling the geometries of snowman shaped PtBA-PTMPT JNPs, the PtBA-PTMPT JNPs are able to self-assemble into micelles containing reversibly oriented individual PtBA-PTMPT JNPs. Additionally, with TMPT as monomer, tri-block JNPs PAA-PTPM-PTPTM were synthesized. The three lobes contained in the tri-block JNPs have different chemistries with complete phase separation, the size of each of these lobes can be independently adjusted, indicating the structural flexibility of these tri-block JNPs. The self-assembly property of the tri-block JNPs is subsequently studied. By utilizing hydrogen bond as the attraction force, the PAA-PTPM-PTPTM JNPs can self-assemble into spherical- and worm-like micelles containing highly oriented individual JNPs. We find that the selfassembly property of the tri-block JNPs is dominated by their precursor, namely the PAA-PTPM snowman shaped JNPs, and the self-assembly properties of three lobes containing JNPs can largely be predicted by two lobed JNPs precursors. Finally, we demonstrated the versatility of PAA-PTPM-TPTM tri-block JNPs by showing that the


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PAA lobe and the TPTM lobe can be separately and independently modified by different chemical reactions.


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ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Experimental methods and synthesis procedures, including snowman and tri-block JNPs synthesis, surface modification and characterization, procedures for selective modification of one Janus lobe by click-reaction. SEM images of the self-assembly of snowman and tri-block JNPs, length distribution analysis of tri-block JNPs selfassembled structures, FTIR of JNPs before and after exposure to surface modifying reagents (PDF). AUTHOR INFORMATION Corresponding Author * [email protected] ORCID Chengjun Kang: 0000-0003-0208-2954 Andrei Honciuc: 0000-0003-2160-2484

Present Addresses


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† Institute of Chemistry and Biotechnology, Zurich University of Applied Sciences, Einsiedlerstrasse 31, 8820 Waedenswil, Switzerland Notes

The authors declare no competing financial interest. ACKNOWLEDGMENT We gratefully acknowledge the financial funding from Metrohm Foundation (Herisau, Switzerland).


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Versatile Tri-Block Janus Nanoparticles: Synthesis and Self-Assembly

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