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This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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Anisotropic Particles Templated by Janus Emulsion
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX DOI: 10.1039/b000000x 5
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Anisotropic particles, with morphology from crescent to moon and size from micrometer to nanometer, are fabricated in batch scale with Janus emulsion as template. The strategy is also useful in the synthesis of Janus particles with chemically distinct hemispheres. Anisotropic particles are attracting amazing interest in the past few years for both fundamental science and industrial applications. The tunable and controllable asymmetric in shape, composition, polarity and other properties makes them possess distinct advantages.1 They are suitable for applications in building blocks for highly ordered lattices, interface stabilizers, catalysts, and sensors of biological, optical, and electrical.2 When it comes to efforts in the synthesis of anisotropic colloidal particles, it began in the last century and became blossoming in the recent ten years.1a, 1c, 3 Early reported strategies are selective surface modification based on two-dimensional apparatus, such as Langmuir-Blodgett deposition, stamp coating, and sputtering.4 However, the large scale application is restricted by the limited amount and equipment dependency. Pickering emulsion route is an offset of this selective masking technique. It transfers the two dimensional technique into a solvent phase.5 Making clever use of the microfluidic device by Weitz et al 1b, 6 has to be mentioned, since the capability of this technique in size uniformity and structural complexity reaches the climax in the synthesis field of non-central symmetric particles.7 However, it is challenging to prepare colloidal particles in nanometer due to the relative large fluidic channels. The micrometer sized particles suffer from limited application, esp. in the biomedical use, such as molecular imaging and biomolecular labeling.1c Employing the selforganization of block copolymers is the first technique to actually realize the preparation of truly nanometer sized anisotropic particles.8 Looking back to the past decades with hundreds of publications on the synthesis of anisotropic particles, there are four main goals that all the scientists are trying to achieve: the first is the ability to precisely control the geometry of the asymmetric particles, the second is to fabricate particles in scale, which is of vital for technique application; the third is the size range from micrometers down to nanometers, which is critical in applications of biomedical; the forth is the simpilicity and low cost, which determines their commercialization and way to real industrial application.1a, 5c Although all the approaches developed are attractive, it would be a breakthrough in material science if This journal is © The Royal Society of Chemistry [year]
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we could develop one technique to cover all four requirements mentioned above. It would also be great appealing to the real word application of these materials. Janus emulsions are highly structured fluids with emulsion drops composed by two hemispheres of immiscible oils. The batch scale preparation in one-step high energy mixing first reported in 2011 by Hasinovic et al.9 was a breakthrough in the field of emulsion science. This development was extended from the microfluidic efforts by the recent discovery that Janus emulsions may form also in the traditional high intensity emulsification process. The topology evolution of Janus droplet has been numerically evaluated by Friberg et al 10 and Kovach et al.11 The quantitative topology parameters were investigated experimentally by our group.12 A variety of topology changes were observed and moreover, the topology parameters including the contact angle, the location of contact plane, and the volume ratio of two hemispheres were in precise agreement with the composition of emulsion. This provides the possibility to exactly control the topology of droplets simply by adjusting the emulsion composition. Moreover, our subsequent work replacing one of the immiscible liquids with a polymerizable monomer found that the size of Janus emulsion droplet reduces from hundreds to a few microns, with the topology remained, simply by adjusting the emulsification energy.13 All these fundamental investigations inspired the idea of the present contribution to employ Janus emulsion droplets as templates for the anisotropic particles, which would cover all the superiorities of scalable, simple, precise topology control, and wide size range.
Scheme 1. A schematic representation of the fabrication of anisotropic particles with Janus emulsion droplets as template.
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A photopolymerizable monomer ethoxylated trimethylolpropane triacrylate (ETPTA) are employed as polymerizable phase, and immiscible fluorocarbon oil (HFE 7200) as the non-polymerizable phase. The continuous phase is [journal], [year], [vol], 00–00 | 1
ChemComm Accepted Manuscript
Published on 26 February 2015. Downloaded by Virginia Tech on 27/02/2015 03:26:37.
Lingling Ge,* Shuhui Lu, Jie Han, Rong Guo*
ChemComm
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DOI: 10.1039/C5CC00935A
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droplets emulsified at the same condition are the same. The Span values of size distributions are less than 2.5 (Table S1), which suggests an acceptable uniformity of emulsion droplets prepared by one-step mixing. Upon UV-induced polymerization, solid particles of poly(ETPTA) are obtained by subsequent removal of fluorocarbon oil. The morphology obtained changes gradually from crescent to moon with increasing ETPTA fraction (Figure1a’-c’), the shape of which agrees well with ETPTA part within mature emulsion droplets. TEM images in the insert show the inner curved surface corresponding to oil/oil interface in emulsion droplets. Size distribution measurements in Figure 1d’ show that the size of generated particles is in excellent agreement with corresponding emulsion droplets with narrow size distribution (Table S1). The results verify the success to employ Janus emulsion droplets as template to the synthesis of anisotropic particles with various morphologies. The size of Janus droplet is varied by adjusting the emulsification energy, aiming at tuning the size of resultant polymer particles. As shown in Figure 1e, f, the mean diameter of emulsion droplets decreases from about 30 µm to 5 µm with acceptable uniformity (Table S2) by increasing the stirring speed. The Janus topology of emulsion remains as shown in the micrographs of Figure S2a-c. The morphology of the resultant particles as shown in Figure S2a’-c’, as well as their size distribution as shown in Figure 1e’, f’, is in excellent agreement with mature emulsion.
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Figure 1. Micrographs of Janus emulsions (a-c), and SEM and TEM (insert) images of the resultant polymer particles (a’- c’) at mass ratios of ETPTA/HFE 7200: a-1/8; b-1/1; c-6/1. Size distributions and the mean size change of Janus emulsion droplets (d-f) and the resultant particles (d’-f’) affected by mass ratios of ETPTA/HFE7200 and by stirring speed. The weight fraction of 0.25 wt % F127 aqueous solutions is 0.33.
Micrographs of Janus droplets with these two immiscible oils as hemispheres are shown in Figure 1a-c. ETPTA spreads partially on the surface of HFE 7200 forming a second hemisphere, where a small dark portion of crescent shape is ETPTA. The morphology of the droplet represents the minima of interfacial free energies between the three liquid phases.12 The interfacial tensions of the two oils with aqueous phase are relatively higher (γETPTA/Aq=3.86 mN/m, γHFE/Aq= 9.35 mN/m) than that of the two oils (γETPTA/HFE= 2.68 mN/m), so the two oil droplets remains paired.1b The asymmetry of two hemispheres is due to the greater affinity of ETPTA to the aqueous phase indicated by the lower interfacial tension. The portion of ETPTA within each droplet develops gradually from “waxing crescent” to “full moon with a hole” as shown in Figure1a-c, by increasing the ratio of ETPTA/HFE 7200. The topology change of the Janus droplet can be extended further as shown in Figure S1. Size distribution measurements show that the effect of ETPTA/HFE 7200 ratio on the droplet size is negligible (Figure 1d), which is reasonable since the size of pure ETPTA and HFE 7200 sphere 2 | Journal Name, [year], [vol], 00–00
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Figure 2. SEM (a-c) and TEM (a’-c’) images of poly(ETPTA) particles prepared from emulsions obtained by sonicate at mass ratios of ETPTA/HFE 7200: a-1/8; b-1/1; c-6/1. The weight fraction of 0.25 wt % F127 aqueous solutions is 0.92.
We succeeded to reduce the diameter of emulsion droplets down to about 500 nm by applying ultrasonic. What is more important, the Janus topology of the emulsion still remains within this challenging size range, as indicated by the SEM and TEM images of polymerized particles (Figure 2). The remained Janus topology within such a wide size range suggests that the interfacial tensions of the three liquids govern the topology of droplet. In addition, the precise control of morphology developing from crescent to moon is also achieved corresponding to the relative amount of two oils in emulsion. The extended topology change with emulsion composition is shown in Figure S3. We have to mention that Janus droplets with size smaller than 200 nm have already been obtained in our lab employing method This journal is © The Royal Society of Chemistry [year]
ChemComm Accepted Manuscript
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aqueous solution employing Pluronic copolymer (F127) as stabilizers.1b, 6a As shown in Scheme 1, Janus emulsion with the two oil phases as the hemispheres of the droplets can be produced in scale by one-step mixing. The volume ratios of the hemispheres within droplets vary in accordance to the initial emulsion composition. Polymer particles can be obtained simply by exposure the emulsion under UV-light, and the particles obtained are of anisotropic shapes since the non-polymerizable part of the droplet acts as a template.7c The morphology of particles can be turned precisely from crescent to moon in agreement with mature emulsion. What is more important, we achieved to change the size of particles from micrometers to nanometers with the topology remained, simply by increasing the energy of emulsification.
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ChemComm View Article Online
of phase inversion concentration (PIC). This low energy method for the production of Janus emulsion ensures the feasibility to prepare anisotropic particles with Janus emulsion as template in both the size ranges of micrometer and nanometer.
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Figure 3. SEM images of a-poly(TPGDA), b- poly(EGDMA), cpoly(TPGDA)-silicone. The inserts in c are element mapping of Si and C. The scale bars in the insert are 200 nm.
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This simple synthesis strategy can also be applied to a huge family of polymeric non-sphere particles, such as poly(TPGDA), poly(EGDMA) as shown in Figure 3a, b. Moreover, Janus particles with different chemicals on both sides would be produced by using two immiscible monomers as oil phases. Figure 3c shows the example of snowman-like Janus particles of poly(TPGDA)-silicone. Elemental mapping images in the insert indicate the spatial distribution of Si and C. In addition, the present technique can be easily extended to anisotropic inorganic/organic complex particles by dispersing inorganic nanoparticles into the organic phases.
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We developed one universal strategy that covering four vital superiorities of scalable, simple, precise topology control, and wide size range to the fabrication of a huge family of anisotropic particles with Janus emulsion as template. The emulsion droplets are obtained in batch scale simply by one-step mixing. Upon UVinduced polymerization, solid polymer particles with anisotropic shapes are formed by the removal of the immiscible oil. The described strategy allows precise control of topology from crescent to moon, simply by adjusting the emulsion composition. Moreover, we also achieve the size control from the challenging range of micrometer down to nanometer, easily by tuning the emulsification energy. In addition, Janus particles with chemically distinct hemispheres can also be fabricated by the combination of two immiscible polymerizable monomers. In a word, this strategy opens an avenue in the field of anisotropic material synthesis.
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Society 2014, 136, 10691; c) F. Tu, D. Lee, Chemical Communications, 2014, 50, 15549; d) W. Gao, A. Pei, R. Dong, J. Wang, Journal of the American Chemical Society 2014, 136, 2276; e) F. Tu, D. Lee, Journal of the American Chemical Society 2014, 136, 9999. a) Jiang, S.; Granick, S. Janus Particle Synthesis, Self-assembly and Applications; The Royal Society of Chemistry: United Kingdom, UK, 2012.; b) M. Lattuada, T. A. Hatton, Nano Today 2011, 6, 286; c) S. Jiang, Q. Chen, M. Tripathy, E. Luijten, K. S. Schweizer, S. Granick, Advanced Materials 2010, 22, 1060; d) X. Pang, C. Wan, M. Wang, Z. Lin, Angewandte Chemie International Edition 2014, 53, 5524; e) F. Liang, C. Zhang, Z. Yang, Advanced Materials 2014, 26, 6944; f) S. C. Glotzer, M. J. Solomon, Nat Mater 2007, 6, 557. a) J.-T. Zhang, X. Chao, S. A. Asher, Journal of the American Chemical Society 2013, 135, 11397; b) M. D. McConnell, M. J. Kraeutler, S. Yang, R. J. Composto, Nano Letters 2010, 10, 603; c) R. T. Chen, B. W. Muir, G. K. Such, A. Postma, K. M. McLean, F. Caruso, Chemical Communications, 2010, 46, 5121. a) B. Liu, W. Wei, X. Qu, Z. Yang, Angewandte Chemie International Edition 2008, 47, 3973; b) C. Huang, X. Shen, Chemical Communications, 2014, 50, 2646; c) A. Walther, A. H. E. Muller, Soft Matter 2008, 4, 663; d) D. Li, Y. He, S. Wang, The Journal of Physical Chemistry C 2009, 113, 12927; e) N. P. Pardhy, B. M. Budhlall, Langmuir 2010, 26, 13130. a) Y. Zhao, H. C. Shum, H. Chen, L. L. A. Adams, Z. Gu, D. A. Weitz, Journal of the American Chemical Society 2011, 133, 8790; b) H. C. Shum, J.-W. Kim, D. A. Weitz, Journal of the American Chemical Society 2008, 130, 9543. a) D. Dendukuri, P. S. Doyle, Advanced Materials 2009, 21, 4071; b) K.-H. Roh, D. C. Martin, J. Lahann, Nat Mater 2005, 4, 759; c) T. Nisisako, T. Torii, Advanced Materials 2007, 19, 1489; d) S. Lone, S. H. Kim, S. W. Nam, S. Park, I. W. Cheong, Langmuir 2010, 26, 17975; e) S. Lone, S. H. Kim, S. W. Nam, S. Park, J. Joo, I. W. Cheong, Chemical Communications, 2011, 47, 2634. a) A. Walther, M. Drechsler, S. Rosenfeldt, L. Harnau, M. Ballauff, V. Abetz, A. H. E. Müller, Journal of the American Chemical Society 2009, 131, 4720; b) A. Walther, K. Matussek, A. H. E. Müller, ACS Nano 2008, 2, 1167; c) L. Cheng, G. Zhang, L. Zhu, D. Chen, M. Jiang, Angewandte Chemie International Edition 2008, 47, 10171. a) H. Hasinovic, S. E. Friberg, Langmuir 2011, 27, 6584; b) H. Hasinovic, S. E. Friberg, G. Rong, Journal of Colloid and Interface Science 2011, 354, 424. a) S. E. Friberg, I. Kovach, J. Koetz, Chemphyschem 2013, 14, 3772; b) S. E. Friberg, Journal of Colloid and Interface Science 2014, 416, 167. I. Kovach, J. Koetz, S. E. Friberg, Colloids and Surfaces aPhysicochemical and Engineering Aspects 2014, 441, 66. L. L. Ge, W. Q. Shao, S. H. Lu, R. Guo, Soft Matter 2014, 10, 4498. L. L. Ge, S. H. Lu, R. Guo, Journal of Colloid and Interface Science 2014, 423, 108.
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School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, Jiangsu, China. E-mail: [email protected]; [email protected] † Electronic Supplementary Information (ESI) available: Experimental details and additional figures. See DOI: 10.1039/b000000x/ 1 a) J. Du, R. K. O'Reilly, Chemical Society Reviews 2011, 40, 2402; b) S.-H. Kim, A. Abbaspourrad, D. A. Weitz, Journal of the American Chemical Society 2011, 133, 5516; c) C. Kaewsaneha, P. Tangboriboonrat, D. Polpanich, M. Eissa, A. Elaissari, Acs Applied Materials & Interfaces 2013, 5, 1857; d) Z. Liu, R. Guo, G. Xu, Z. Huang, L.-T. Yan, Nano Letters 2014, 14, 6910. 2 a) G. Loget, D. Zigah, L. Bouffier, N. Sojic, A. Kuhn, Accounts of Chemical Research 2013, 46, 2513; b) H. Liu, C.-H. Hsu, Z. Lin, W. Shan, J. Wang, J. Jiang, M. Huang, B. Lotz, X. Yu, W.-B. Zhang, K. Yue, S. Z. D. Cheng, Journal of the American Chemical
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3
ChemComm Accepted Manuscript
DOI: 10.1039/C5CC00935A
ChemComm Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: L. Ge, S. Lu, J. Han and R. Guo, Chem. Commun., 2015, DOI: 10.1039/C5CC00935A.
This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
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DOI: 10.1039/C5CC00935A
Cite this: DOI: 10.1039/c0xx00000x
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Anisotropic Particles Templated by Janus Emulsion
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX DOI: 10.1039/b000000x 5
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Anisotropic particles, with morphology from crescent to moon and size from micrometer to nanometer, are fabricated in batch scale with Janus emulsion as template. The strategy is also useful in the synthesis of Janus particles with chemically distinct hemispheres. Anisotropic particles are attracting amazing interest in the past few years for both fundamental science and industrial applications. The tunable and controllable asymmetric in shape, composition, polarity and other properties makes them possess distinct advantages.1 They are suitable for applications in building blocks for highly ordered lattices, interface stabilizers, catalysts, and sensors of biological, optical, and electrical.2 When it comes to efforts in the synthesis of anisotropic colloidal particles, it began in the last century and became blossoming in the recent ten years.1a, 1c, 3 Early reported strategies are selective surface modification based on two-dimensional apparatus, such as Langmuir-Blodgett deposition, stamp coating, and sputtering.4 However, the large scale application is restricted by the limited amount and equipment dependency. Pickering emulsion route is an offset of this selective masking technique. It transfers the two dimensional technique into a solvent phase.5 Making clever use of the microfluidic device by Weitz et al 1b, 6 has to be mentioned, since the capability of this technique in size uniformity and structural complexity reaches the climax in the synthesis field of non-central symmetric particles.7 However, it is challenging to prepare colloidal particles in nanometer due to the relative large fluidic channels. The micrometer sized particles suffer from limited application, esp. in the biomedical use, such as molecular imaging and biomolecular labeling.1c Employing the selforganization of block copolymers is the first technique to actually realize the preparation of truly nanometer sized anisotropic particles.8 Looking back to the past decades with hundreds of publications on the synthesis of anisotropic particles, there are four main goals that all the scientists are trying to achieve: the first is the ability to precisely control the geometry of the asymmetric particles, the second is to fabricate particles in scale, which is of vital for technique application; the third is the size range from micrometers down to nanometers, which is critical in applications of biomedical; the forth is the simpilicity and low cost, which determines their commercialization and way to real industrial application.1a, 5c Although all the approaches developed are attractive, it would be a breakthrough in material science if This journal is © The Royal Society of Chemistry [year]
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we could develop one technique to cover all four requirements mentioned above. It would also be great appealing to the real word application of these materials. Janus emulsions are highly structured fluids with emulsion drops composed by two hemispheres of immiscible oils. The batch scale preparation in one-step high energy mixing first reported in 2011 by Hasinovic et al.9 was a breakthrough in the field of emulsion science. This development was extended from the microfluidic efforts by the recent discovery that Janus emulsions may form also in the traditional high intensity emulsification process. The topology evolution of Janus droplet has been numerically evaluated by Friberg et al 10 and Kovach et al.11 The quantitative topology parameters were investigated experimentally by our group.12 A variety of topology changes were observed and moreover, the topology parameters including the contact angle, the location of contact plane, and the volume ratio of two hemispheres were in precise agreement with the composition of emulsion. This provides the possibility to exactly control the topology of droplets simply by adjusting the emulsion composition. Moreover, our subsequent work replacing one of the immiscible liquids with a polymerizable monomer found that the size of Janus emulsion droplet reduces from hundreds to a few microns, with the topology remained, simply by adjusting the emulsification energy.13 All these fundamental investigations inspired the idea of the present contribution to employ Janus emulsion droplets as templates for the anisotropic particles, which would cover all the superiorities of scalable, simple, precise topology control, and wide size range.
Scheme 1. A schematic representation of the fabrication of anisotropic particles with Janus emulsion droplets as template.
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A photopolymerizable monomer ethoxylated trimethylolpropane triacrylate (ETPTA) are employed as polymerizable phase, and immiscible fluorocarbon oil (HFE 7200) as the non-polymerizable phase. The continuous phase is [journal], [year], [vol], 00–00 | 1
ChemComm Accepted Manuscript
Published on 26 February 2015. Downloaded by Virginia Tech on 27/02/2015 03:26:37.
Lingling Ge,* Shuhui Lu, Jie Han, Rong Guo*
ChemComm
Page 2 of 3 View Article Online
DOI: 10.1039/C5CC00935A
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droplets emulsified at the same condition are the same. The Span values of size distributions are less than 2.5 (Table S1), which suggests an acceptable uniformity of emulsion droplets prepared by one-step mixing. Upon UV-induced polymerization, solid particles of poly(ETPTA) are obtained by subsequent removal of fluorocarbon oil. The morphology obtained changes gradually from crescent to moon with increasing ETPTA fraction (Figure1a’-c’), the shape of which agrees well with ETPTA part within mature emulsion droplets. TEM images in the insert show the inner curved surface corresponding to oil/oil interface in emulsion droplets. Size distribution measurements in Figure 1d’ show that the size of generated particles is in excellent agreement with corresponding emulsion droplets with narrow size distribution (Table S1). The results verify the success to employ Janus emulsion droplets as template to the synthesis of anisotropic particles with various morphologies. The size of Janus droplet is varied by adjusting the emulsification energy, aiming at tuning the size of resultant polymer particles. As shown in Figure 1e, f, the mean diameter of emulsion droplets decreases from about 30 µm to 5 µm with acceptable uniformity (Table S2) by increasing the stirring speed. The Janus topology of emulsion remains as shown in the micrographs of Figure S2a-c. The morphology of the resultant particles as shown in Figure S2a’-c’, as well as their size distribution as shown in Figure 1e’, f’, is in excellent agreement with mature emulsion.
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Figure 1. Micrographs of Janus emulsions (a-c), and SEM and TEM (insert) images of the resultant polymer particles (a’- c’) at mass ratios of ETPTA/HFE 7200: a-1/8; b-1/1; c-6/1. Size distributions and the mean size change of Janus emulsion droplets (d-f) and the resultant particles (d’-f’) affected by mass ratios of ETPTA/HFE7200 and by stirring speed. The weight fraction of 0.25 wt % F127 aqueous solutions is 0.33.
Micrographs of Janus droplets with these two immiscible oils as hemispheres are shown in Figure 1a-c. ETPTA spreads partially on the surface of HFE 7200 forming a second hemisphere, where a small dark portion of crescent shape is ETPTA. The morphology of the droplet represents the minima of interfacial free energies between the three liquid phases.12 The interfacial tensions of the two oils with aqueous phase are relatively higher (γETPTA/Aq=3.86 mN/m, γHFE/Aq= 9.35 mN/m) than that of the two oils (γETPTA/HFE= 2.68 mN/m), so the two oil droplets remains paired.1b The asymmetry of two hemispheres is due to the greater affinity of ETPTA to the aqueous phase indicated by the lower interfacial tension. The portion of ETPTA within each droplet develops gradually from “waxing crescent” to “full moon with a hole” as shown in Figure1a-c, by increasing the ratio of ETPTA/HFE 7200. The topology change of the Janus droplet can be extended further as shown in Figure S1. Size distribution measurements show that the effect of ETPTA/HFE 7200 ratio on the droplet size is negligible (Figure 1d), which is reasonable since the size of pure ETPTA and HFE 7200 sphere 2 | Journal Name, [year], [vol], 00–00
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Figure 2. SEM (a-c) and TEM (a’-c’) images of poly(ETPTA) particles prepared from emulsions obtained by sonicate at mass ratios of ETPTA/HFE 7200: a-1/8; b-1/1; c-6/1. The weight fraction of 0.25 wt % F127 aqueous solutions is 0.92.
We succeeded to reduce the diameter of emulsion droplets down to about 500 nm by applying ultrasonic. What is more important, the Janus topology of the emulsion still remains within this challenging size range, as indicated by the SEM and TEM images of polymerized particles (Figure 2). The remained Janus topology within such a wide size range suggests that the interfacial tensions of the three liquids govern the topology of droplet. In addition, the precise control of morphology developing from crescent to moon is also achieved corresponding to the relative amount of two oils in emulsion. The extended topology change with emulsion composition is shown in Figure S3. We have to mention that Janus droplets with size smaller than 200 nm have already been obtained in our lab employing method This journal is © The Royal Society of Chemistry [year]
ChemComm Accepted Manuscript
5
aqueous solution employing Pluronic copolymer (F127) as stabilizers.1b, 6a As shown in Scheme 1, Janus emulsion with the two oil phases as the hemispheres of the droplets can be produced in scale by one-step mixing. The volume ratios of the hemispheres within droplets vary in accordance to the initial emulsion composition. Polymer particles can be obtained simply by exposure the emulsion under UV-light, and the particles obtained are of anisotropic shapes since the non-polymerizable part of the droplet acts as a template.7c The morphology of particles can be turned precisely from crescent to moon in agreement with mature emulsion. What is more important, we achieved to change the size of particles from micrometers to nanometers with the topology remained, simply by increasing the energy of emulsification.
Page 3 of 3
ChemComm View Article Online
of phase inversion concentration (PIC). This low energy method for the production of Janus emulsion ensures the feasibility to prepare anisotropic particles with Janus emulsion as template in both the size ranges of micrometer and nanometer.
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Figure 3. SEM images of a-poly(TPGDA), b- poly(EGDMA), cpoly(TPGDA)-silicone. The inserts in c are element mapping of Si and C. The scale bars in the insert are 200 nm.
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This simple synthesis strategy can also be applied to a huge family of polymeric non-sphere particles, such as poly(TPGDA), poly(EGDMA) as shown in Figure 3a, b. Moreover, Janus particles with different chemicals on both sides would be produced by using two immiscible monomers as oil phases. Figure 3c shows the example of snowman-like Janus particles of poly(TPGDA)-silicone. Elemental mapping images in the insert indicate the spatial distribution of Si and C. In addition, the present technique can be easily extended to anisotropic inorganic/organic complex particles by dispersing inorganic nanoparticles into the organic phases.
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We developed one universal strategy that covering four vital superiorities of scalable, simple, precise topology control, and wide size range to the fabrication of a huge family of anisotropic particles with Janus emulsion as template. The emulsion droplets are obtained in batch scale simply by one-step mixing. Upon UVinduced polymerization, solid polymer particles with anisotropic shapes are formed by the removal of the immiscible oil. The described strategy allows precise control of topology from crescent to moon, simply by adjusting the emulsion composition. Moreover, we also achieve the size control from the challenging range of micrometer down to nanometer, easily by tuning the emulsification energy. In addition, Janus particles with chemically distinct hemispheres can also be fabricated by the combination of two immiscible polymerizable monomers. In a word, this strategy opens an avenue in the field of anisotropic material synthesis.
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DOI: 10.1039/C5CC00935A
