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Wenbin Zhang - One of the best experts on this subject based on the ideXlab platform.

  • self assembly of fullerene based janus particles in solution effects of Molecular architecture and solvent
    Chemistry: A European Journal, 2014
    Co-Authors: Zhiwei Lin, Pengtao Lu, Chihhao Hsu, Kan Yue, Xuehui Dong, Chrys Wesdemiotis, Wenbin Zhang, Hao Liu, Kai Guo
    Abstract:

    Two Molecular Janus particles based on amphiphilic [60]fullerene (C60) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC60), and a hydrophobic C60 in different ratios and have distinct Molecular architectures: 1:1 (AC60–C60) and 1:2 (AC60–2C60). These Molecular Janus particles can self-assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC60–C60 and AC60–2C60 in tetrahydrofuran, in a mixture of N,N-dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC60–C60 and AC60–2C60, respectively. A mechanism of formation was tentatively proposed based on the effects of Molecular architecture and solvent polarity on self-assembly. Since the concept of “Janus grains” was introduced by de Gennes and co-workers, tremendous attention has been paid on their symmetry-breaking structures, self-assembly behavior, and unique properties. Progress have been made on the design and synthesis of organic/inorganic micellar or colloidal Janus particles with the availability of sophisticated synthetic techniques. In those studies, the size of these Janus particles usually ranges from hundreds of nanometers to micrometers. If a Janus grain is based on a well-defined Molecular structure with nanometer size and persistent shape, it may be considered a Molecular Janus particle (MJP). There are two types of symmetry breaking for MJPs: geometric and chemical symmetry. Various efforts have so far been made to prepare MJPs with flexible conformations, example being amphiphilic dendrimers, block copolymers, and polymeric brushes, all of which can self-assemble into intriguing structures in bulk and solution. c] However, the construction of MJPs as precisely-defined Molecular nanoparticles of fixed shape, volume, and functionality that can retain their asymmetrical geometry and chemistry during self-assembly remains largely unexplored. Recently, Molecular nanoparticles have been conceptually proposed as the elemental nano-building blocks, or “nanoatoms” for building precise macromolecules. Nano-atoms are shapeand volume-persistent Molecular nanoparticles, such as [60]fullerene (C60), polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), and folded globular proteins. They possess precisely-defined primary chemical structures and surface functionalities, and are ready for precise synthesis of giant molecules utilizing efficient methods such as the sequential click approach. MJPs based on POSS and POM derivatives have been reported to self-organize into bilayer structures in the bulk. Yet the examples are rare. It is thus of interest to further expand the scope of MJPs and investigate how they can be directed to assemble into different hierarchical structures, and how to further promote transformations and amplifications of microscopic functionalities towards macroscopic properties. Among those Molecular nanoparticles, C60 is a spherical nanoparticle with truncated icosahedral (Ih) symmetry. Surfaces of C60 can be precisely functionalized by regioselective chemical reactions. Several C60-based amphiphiles have exhibited interesting self-assembly behaviors in solution. For instance, a series of pentasubstituted fullerene potassium salts can selfassemble into bilayer vesicles in THF/water. We have recently synthesized new C60 derivatives bearing ten carboxylic acid functional group (AC60) and further tethered them with one or two polystyrene (PS) tails to construct a new class of giant surfactants. With increasing initial Molecular Concentration or the PS tail length, micellar morphologies can be tuned from spheres, to cylinders, and finally, to vesicles. The PS tails are recognized to be stretched in their micelles, similar to small Molecular surfactants. Herein, we report on the design, synthesis, and self-assembly of two new MJPs based on C60, namely, AC60–C60 and AC60– 2C60, by clicking a hydrophilic AC60 with one or two hydrophobic C60. The resulting amphiphilic MJPs are expected to exhibit self-assembly behaviors that depend on the solvent system. AC60–C60 and AC60–2C60 are synthesized by combining the regioselective Bingel–Hirsh reaction and the highly efficient Huisgen 1,3-dipolar cycloaddition click reaction, as outlined in Scheme 1. Monotethered C60 derivative 2 with an azide group was prepared by reaction of compound 1 with C60 under the Bingel reaction conditions. Precisely defined [5:1]-hexakisadducts of C60, with one (3a) or two (3b) terminal alkyne groups and ten protected carboxylic acid groups, were synthesized based on the procedures described in our previous publication. The azide–alkyne click reaction was successfully utilized to link the monofunctionalized C60 (2) with the surface-modified C60 derivatives (3a–b) in high yields ( 80%), resulting in conjugates of a protected carboxylic acid group functionalized C60 tethered with one (4a, tC60–C60) or two C60s (4b, tC60–2C60). The disappearance of the azide resonance at ca. 2100 cm 1 and the alkyne resonance at ca. 3300 cm 1 in the IR spectra of 4a–b provides evidence of the successful reaction between 2 and 3a–b (see Figure S1 in [a] Z. Lin, P. Lu, C.-H. Hsu, Dr. K. Yue, Dr. X.-H. Dong, H. Liu, K. Guo, Prof. C. Wesdemiotis, Dr. W.-B. Zhang, Dr. X. Yu, Prof. S. Z. D. Cheng Department of Polymer Science College of Polymer Science and Polymer Engineering The University of Akron, 170 University Ave. Akron, Ohio, 44325-3909 (USA) Fax: (+1)330-972-8626 E-mail : wenbin@pku.edu.cn xy5@zips.uakron.edu scheng@uakron.edu [b] Prof. C. Wesdemiotis Department of Chemistry The University of Akron Akron, Ohio, 44325-3601 (USA) [c] Dr. W.-B. Zhang Key Laboratory of Polymer Chemistry & Physics of Ministry of Education College of Chemistry and Molecular Engineering Center for Soft Matter Science and Engineering Peking University, Beijing 100871 (P. R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201402697. Chem. Eur. J. 2014, 20, 11630 – 11635 www.chemeurj.org 2014 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 11631 Communication

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC60) tethered with one or two polystyrene (PS) chain(s) at one junction point (PSn–AC60 and 2PSn–AC60). The synthesis highlighted the regiospecific multiaddition reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C60 and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equ...

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC(60)) tethered with one or two polystyrene (PS) chain(s) at one junction point (PS(n)-AC(60) and 2PS(n)-AC(60)). The synthesis highlighted the regiospecific multiaddition reaction for C(60) surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C(60) and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equal or less than 0.25 (wt) %, micellar morphology of the series of PS(n)-AC(60) studied was always spheres, while the series of 2PS(n)-AC(60) formed vesicles. Particularly, PS(44)-AC(60) and 2PS(23)-AC(60) are synthesized as a topological isomer pair of these shape amphiphiles. PS(44)-AC(60) formed spherical micelles while 2PS(23)-AC(60) generated bilayer vesicles under identical conditions. The difference in the self-assembly of PS(n)-AC(60) and 2PS(n)-AC(60) was understood by the Molecular shape aspect ratio. The stretching ratio of PS tails decreased with increasing PS tail length in the spherical micelles of PS(n)-AC(60), indicating a micellar behavior that changes from small Molecular surfactant-like to amphiphilic block copolymer-like. For the series of PS(n)-AC(60) in the high Molecular Concentration range [>0.25 (wt) %], their micellar morphological formation of spheres, cylinders, and vesicles was critically dependent upon both the initial Molecular Concentration and the PS tail length. On the other hand, the series of 2PS(n)-AC(60) remained in the state of bilayer vesicles in the same Concentration range. Combining both of the experimental results obtained in the low and high Molecular Concentrations, a systematic morphological phase diagram was constructed for the series of PS(n)-AC(60) with different PS tail lengths. The versatile and Concentration-sensitive phase behaviors of these Molecular shape amphiphiles are unique and have not been systematically explored in the traditional surfactants and block copolymers systems.

Stephen Z. D. Cheng - One of the best experts on this subject based on the ideXlab platform.

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC60) tethered with one or two polystyrene (PS) chain(s) at one junction point (PSn–AC60 and 2PSn–AC60). The synthesis highlighted the regiospecific multiaddition reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C60 and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equ...

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC(60)) tethered with one or two polystyrene (PS) chain(s) at one junction point (PS(n)-AC(60) and 2PS(n)-AC(60)). The synthesis highlighted the regiospecific multiaddition reaction for C(60) surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C(60) and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equal or less than 0.25 (wt) %, micellar morphology of the series of PS(n)-AC(60) studied was always spheres, while the series of 2PS(n)-AC(60) formed vesicles. Particularly, PS(44)-AC(60) and 2PS(23)-AC(60) are synthesized as a topological isomer pair of these shape amphiphiles. PS(44)-AC(60) formed spherical micelles while 2PS(23)-AC(60) generated bilayer vesicles under identical conditions. The difference in the self-assembly of PS(n)-AC(60) and 2PS(n)-AC(60) was understood by the Molecular shape aspect ratio. The stretching ratio of PS tails decreased with increasing PS tail length in the spherical micelles of PS(n)-AC(60), indicating a micellar behavior that changes from small Molecular surfactant-like to amphiphilic block copolymer-like. For the series of PS(n)-AC(60) in the high Molecular Concentration range [>0.25 (wt) %], their micellar morphological formation of spheres, cylinders, and vesicles was critically dependent upon both the initial Molecular Concentration and the PS tail length. On the other hand, the series of 2PS(n)-AC(60) remained in the state of bilayer vesicles in the same Concentration range. Combining both of the experimental results obtained in the low and high Molecular Concentrations, a systematic morphological phase diagram was constructed for the series of PS(n)-AC(60) with different PS tail lengths. The versatile and Concentration-sensitive phase behaviors of these Molecular shape amphiphiles are unique and have not been systematically explored in the traditional surfactants and block copolymers systems.

Gerwin J Puppels - One of the best experts on this subject based on the ideXlab platform.

Hao Liu - One of the best experts on this subject based on the ideXlab platform.

  • self assembly of fullerene based janus particles in solution effects of Molecular architecture and solvent
    Chemistry: A European Journal, 2014
    Co-Authors: Zhiwei Lin, Pengtao Lu, Chihhao Hsu, Kan Yue, Xuehui Dong, Chrys Wesdemiotis, Wenbin Zhang, Hao Liu, Kai Guo
    Abstract:

    Two Molecular Janus particles based on amphiphilic [60]fullerene (C60) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC60), and a hydrophobic C60 in different ratios and have distinct Molecular architectures: 1:1 (AC60–C60) and 1:2 (AC60–2C60). These Molecular Janus particles can self-assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC60–C60 and AC60–2C60 in tetrahydrofuran, in a mixture of N,N-dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC60–C60 and AC60–2C60, respectively. A mechanism of formation was tentatively proposed based on the effects of Molecular architecture and solvent polarity on self-assembly. Since the concept of “Janus grains” was introduced by de Gennes and co-workers, tremendous attention has been paid on their symmetry-breaking structures, self-assembly behavior, and unique properties. Progress have been made on the design and synthesis of organic/inorganic micellar or colloidal Janus particles with the availability of sophisticated synthetic techniques. In those studies, the size of these Janus particles usually ranges from hundreds of nanometers to micrometers. If a Janus grain is based on a well-defined Molecular structure with nanometer size and persistent shape, it may be considered a Molecular Janus particle (MJP). There are two types of symmetry breaking for MJPs: geometric and chemical symmetry. Various efforts have so far been made to prepare MJPs with flexible conformations, example being amphiphilic dendrimers, block copolymers, and polymeric brushes, all of which can self-assemble into intriguing structures in bulk and solution. c] However, the construction of MJPs as precisely-defined Molecular nanoparticles of fixed shape, volume, and functionality that can retain their asymmetrical geometry and chemistry during self-assembly remains largely unexplored. Recently, Molecular nanoparticles have been conceptually proposed as the elemental nano-building blocks, or “nanoatoms” for building precise macromolecules. Nano-atoms are shapeand volume-persistent Molecular nanoparticles, such as [60]fullerene (C60), polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), and folded globular proteins. They possess precisely-defined primary chemical structures and surface functionalities, and are ready for precise synthesis of giant molecules utilizing efficient methods such as the sequential click approach. MJPs based on POSS and POM derivatives have been reported to self-organize into bilayer structures in the bulk. Yet the examples are rare. It is thus of interest to further expand the scope of MJPs and investigate how they can be directed to assemble into different hierarchical structures, and how to further promote transformations and amplifications of microscopic functionalities towards macroscopic properties. Among those Molecular nanoparticles, C60 is a spherical nanoparticle with truncated icosahedral (Ih) symmetry. Surfaces of C60 can be precisely functionalized by regioselective chemical reactions. Several C60-based amphiphiles have exhibited interesting self-assembly behaviors in solution. For instance, a series of pentasubstituted fullerene potassium salts can selfassemble into bilayer vesicles in THF/water. We have recently synthesized new C60 derivatives bearing ten carboxylic acid functional group (AC60) and further tethered them with one or two polystyrene (PS) tails to construct a new class of giant surfactants. With increasing initial Molecular Concentration or the PS tail length, micellar morphologies can be tuned from spheres, to cylinders, and finally, to vesicles. The PS tails are recognized to be stretched in their micelles, similar to small Molecular surfactants. Herein, we report on the design, synthesis, and self-assembly of two new MJPs based on C60, namely, AC60–C60 and AC60– 2C60, by clicking a hydrophilic AC60 with one or two hydrophobic C60. The resulting amphiphilic MJPs are expected to exhibit self-assembly behaviors that depend on the solvent system. AC60–C60 and AC60–2C60 are synthesized by combining the regioselective Bingel–Hirsh reaction and the highly efficient Huisgen 1,3-dipolar cycloaddition click reaction, as outlined in Scheme 1. Monotethered C60 derivative 2 with an azide group was prepared by reaction of compound 1 with C60 under the Bingel reaction conditions. Precisely defined [5:1]-hexakisadducts of C60, with one (3a) or two (3b) terminal alkyne groups and ten protected carboxylic acid groups, were synthesized based on the procedures described in our previous publication. The azide–alkyne click reaction was successfully utilized to link the monofunctionalized C60 (2) with the surface-modified C60 derivatives (3a–b) in high yields ( 80%), resulting in conjugates of a protected carboxylic acid group functionalized C60 tethered with one (4a, tC60–C60) or two C60s (4b, tC60–2C60). The disappearance of the azide resonance at ca. 2100 cm 1 and the alkyne resonance at ca. 3300 cm 1 in the IR spectra of 4a–b provides evidence of the successful reaction between 2 and 3a–b (see Figure S1 in [a] Z. Lin, P. Lu, C.-H. Hsu, Dr. K. Yue, Dr. X.-H. Dong, H. Liu, K. Guo, Prof. C. Wesdemiotis, Dr. W.-B. Zhang, Dr. X. Yu, Prof. S. Z. D. Cheng Department of Polymer Science College of Polymer Science and Polymer Engineering The University of Akron, 170 University Ave. Akron, Ohio, 44325-3909 (USA) Fax: (+1)330-972-8626 E-mail : wenbin@pku.edu.cn xy5@zips.uakron.edu scheng@uakron.edu [b] Prof. C. Wesdemiotis Department of Chemistry The University of Akron Akron, Ohio, 44325-3601 (USA) [c] Dr. W.-B. Zhang Key Laboratory of Polymer Chemistry & Physics of Ministry of Education College of Chemistry and Molecular Engineering Center for Soft Matter Science and Engineering Peking University, Beijing 100871 (P. R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201402697. Chem. Eur. J. 2014, 20, 11630 – 11635 www.chemeurj.org 2014 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 11631 Communication

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC60) tethered with one or two polystyrene (PS) chain(s) at one junction point (PSn–AC60 and 2PSn–AC60). The synthesis highlighted the regiospecific multiaddition reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C60 and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equ...

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC(60)) tethered with one or two polystyrene (PS) chain(s) at one junction point (PS(n)-AC(60) and 2PS(n)-AC(60)). The synthesis highlighted the regiospecific multiaddition reaction for C(60) surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C(60) and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equal or less than 0.25 (wt) %, micellar morphology of the series of PS(n)-AC(60) studied was always spheres, while the series of 2PS(n)-AC(60) formed vesicles. Particularly, PS(44)-AC(60) and 2PS(23)-AC(60) are synthesized as a topological isomer pair of these shape amphiphiles. PS(44)-AC(60) formed spherical micelles while 2PS(23)-AC(60) generated bilayer vesicles under identical conditions. The difference in the self-assembly of PS(n)-AC(60) and 2PS(n)-AC(60) was understood by the Molecular shape aspect ratio. The stretching ratio of PS tails decreased with increasing PS tail length in the spherical micelles of PS(n)-AC(60), indicating a micellar behavior that changes from small Molecular surfactant-like to amphiphilic block copolymer-like. For the series of PS(n)-AC(60) in the high Molecular Concentration range [>0.25 (wt) %], their micellar morphological formation of spheres, cylinders, and vesicles was critically dependent upon both the initial Molecular Concentration and the PS tail length. On the other hand, the series of 2PS(n)-AC(60) remained in the state of bilayer vesicles in the same Concentration range. Combining both of the experimental results obtained in the low and high Molecular Concentrations, a systematic morphological phase diagram was constructed for the series of PS(n)-AC(60) with different PS tail lengths. The versatile and Concentration-sensitive phase behaviors of these Molecular shape amphiphiles are unique and have not been systematically explored in the traditional surfactants and block copolymers systems.

Chrys Wesdemiotis - One of the best experts on this subject based on the ideXlab platform.

  • self assembly of fullerene based janus particles in solution effects of Molecular architecture and solvent
    Chemistry: A European Journal, 2014
    Co-Authors: Zhiwei Lin, Pengtao Lu, Chihhao Hsu, Kan Yue, Xuehui Dong, Chrys Wesdemiotis, Wenbin Zhang, Hao Liu, Kai Guo
    Abstract:

    Two Molecular Janus particles based on amphiphilic [60]fullerene (C60) derivatives were designed and synthesized by using the regioselective Bingel–Hirsh reaction and the click reaction. These particles contain carboxylic acid functional groups, a hydrophilic fullerene (AC60), and a hydrophobic C60 in different ratios and have distinct Molecular architectures: 1:1 (AC60–C60) and 1:2 (AC60–2C60). These Molecular Janus particles can self-assemble in solution to form aggregates with various types of micellar morphology. Whereas vesicular morphology was observed for both AC60–C60 and AC60–2C60 in tetrahydrofuran, in a mixture of N,N-dimethylformamide (DMF)/water, spherical micelles and cylindrical micelles were observed for AC60–C60 and AC60–2C60, respectively. A mechanism of formation was tentatively proposed based on the effects of Molecular architecture and solvent polarity on self-assembly. Since the concept of “Janus grains” was introduced by de Gennes and co-workers, tremendous attention has been paid on their symmetry-breaking structures, self-assembly behavior, and unique properties. Progress have been made on the design and synthesis of organic/inorganic micellar or colloidal Janus particles with the availability of sophisticated synthetic techniques. In those studies, the size of these Janus particles usually ranges from hundreds of nanometers to micrometers. If a Janus grain is based on a well-defined Molecular structure with nanometer size and persistent shape, it may be considered a Molecular Janus particle (MJP). There are two types of symmetry breaking for MJPs: geometric and chemical symmetry. Various efforts have so far been made to prepare MJPs with flexible conformations, example being amphiphilic dendrimers, block copolymers, and polymeric brushes, all of which can self-assemble into intriguing structures in bulk and solution. c] However, the construction of MJPs as precisely-defined Molecular nanoparticles of fixed shape, volume, and functionality that can retain their asymmetrical geometry and chemistry during self-assembly remains largely unexplored. Recently, Molecular nanoparticles have been conceptually proposed as the elemental nano-building blocks, or “nanoatoms” for building precise macromolecules. Nano-atoms are shapeand volume-persistent Molecular nanoparticles, such as [60]fullerene (C60), polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), and folded globular proteins. They possess precisely-defined primary chemical structures and surface functionalities, and are ready for precise synthesis of giant molecules utilizing efficient methods such as the sequential click approach. MJPs based on POSS and POM derivatives have been reported to self-organize into bilayer structures in the bulk. Yet the examples are rare. It is thus of interest to further expand the scope of MJPs and investigate how they can be directed to assemble into different hierarchical structures, and how to further promote transformations and amplifications of microscopic functionalities towards macroscopic properties. Among those Molecular nanoparticles, C60 is a spherical nanoparticle with truncated icosahedral (Ih) symmetry. Surfaces of C60 can be precisely functionalized by regioselective chemical reactions. Several C60-based amphiphiles have exhibited interesting self-assembly behaviors in solution. For instance, a series of pentasubstituted fullerene potassium salts can selfassemble into bilayer vesicles in THF/water. We have recently synthesized new C60 derivatives bearing ten carboxylic acid functional group (AC60) and further tethered them with one or two polystyrene (PS) tails to construct a new class of giant surfactants. With increasing initial Molecular Concentration or the PS tail length, micellar morphologies can be tuned from spheres, to cylinders, and finally, to vesicles. The PS tails are recognized to be stretched in their micelles, similar to small Molecular surfactants. Herein, we report on the design, synthesis, and self-assembly of two new MJPs based on C60, namely, AC60–C60 and AC60– 2C60, by clicking a hydrophilic AC60 with one or two hydrophobic C60. The resulting amphiphilic MJPs are expected to exhibit self-assembly behaviors that depend on the solvent system. AC60–C60 and AC60–2C60 are synthesized by combining the regioselective Bingel–Hirsh reaction and the highly efficient Huisgen 1,3-dipolar cycloaddition click reaction, as outlined in Scheme 1. Monotethered C60 derivative 2 with an azide group was prepared by reaction of compound 1 with C60 under the Bingel reaction conditions. Precisely defined [5:1]-hexakisadducts of C60, with one (3a) or two (3b) terminal alkyne groups and ten protected carboxylic acid groups, were synthesized based on the procedures described in our previous publication. The azide–alkyne click reaction was successfully utilized to link the monofunctionalized C60 (2) with the surface-modified C60 derivatives (3a–b) in high yields ( 80%), resulting in conjugates of a protected carboxylic acid group functionalized C60 tethered with one (4a, tC60–C60) or two C60s (4b, tC60–2C60). The disappearance of the azide resonance at ca. 2100 cm 1 and the alkyne resonance at ca. 3300 cm 1 in the IR spectra of 4a–b provides evidence of the successful reaction between 2 and 3a–b (see Figure S1 in [a] Z. Lin, P. Lu, C.-H. Hsu, Dr. K. Yue, Dr. X.-H. Dong, H. Liu, K. Guo, Prof. C. Wesdemiotis, Dr. W.-B. Zhang, Dr. X. Yu, Prof. S. Z. D. Cheng Department of Polymer Science College of Polymer Science and Polymer Engineering The University of Akron, 170 University Ave. Akron, Ohio, 44325-3909 (USA) Fax: (+1)330-972-8626 E-mail : wenbin@pku.edu.cn xy5@zips.uakron.edu scheng@uakron.edu [b] Prof. C. Wesdemiotis Department of Chemistry The University of Akron Akron, Ohio, 44325-3601 (USA) [c] Dr. W.-B. Zhang Key Laboratory of Polymer Chemistry & Physics of Ministry of Education College of Chemistry and Molecular Engineering Center for Soft Matter Science and Engineering Peking University, Beijing 100871 (P. R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201402697. Chem. Eur. J. 2014, 20, 11630 – 11635 www.chemeurj.org 2014 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 11631 Communication

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC60) tethered with one or two polystyrene (PS) chain(s) at one junction point (PSn–AC60 and 2PSn–AC60). The synthesis highlighted the regiospecific multiaddition reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C60 and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equ...

  • giant Molecular shape amphiphiles based on polystyrene hydrophilic 60 fullerene conjugates click synthesis solution self assembly and phase behavior
    Journal of the American Chemical Society, 2012
    Co-Authors: Wenbin Zhang, Kan Yue, Chrys Wesdemiotis, Hao Liu, Yu Xin, Chienlung Wang, Stephen Z. D. Cheng
    Abstract:

    This paper reports a comprehensive study on the synthesis and self-assembly of two model series of Molecular shape amphiphiles, namely, hydrophilic [60]fullerene (AC(60)) tethered with one or two polystyrene (PS) chain(s) at one junction point (PS(n)-AC(60) and 2PS(n)-AC(60)). The synthesis highlighted the regiospecific multiaddition reaction for C(60) surface functionalization and the Huisgen 1,3-dipolar cycloaddition between alkyne functionalized C(60) and azide functionalized polymer to give rise to shape amphiphiles with precisely defined surface chemistry and Molecular topology. When 1,4-dioxane/DMF mixture was used as the common solvent and water as the selective solvent, these shape amphiphiles exhibited versatile self-assembled micellar morphologies which can be tuned by changing various parameters, such as Molecular topology, polymer tail length, and initial Molecular Concentration, as revealed by transmission electron microscopy and light scattering experiments. In the low Molecular Concentration range of equal or less than 0.25 (wt) %, micellar morphology of the series of PS(n)-AC(60) studied was always spheres, while the series of 2PS(n)-AC(60) formed vesicles. Particularly, PS(44)-AC(60) and 2PS(23)-AC(60) are synthesized as a topological isomer pair of these shape amphiphiles. PS(44)-AC(60) formed spherical micelles while 2PS(23)-AC(60) generated bilayer vesicles under identical conditions. The difference in the self-assembly of PS(n)-AC(60) and 2PS(n)-AC(60) was understood by the Molecular shape aspect ratio. The stretching ratio of PS tails decreased with increasing PS tail length in the spherical micelles of PS(n)-AC(60), indicating a micellar behavior that changes from small Molecular surfactant-like to amphiphilic block copolymer-like. For the series of PS(n)-AC(60) in the high Molecular Concentration range [>0.25 (wt) %], their micellar morphological formation of spheres, cylinders, and vesicles was critically dependent upon both the initial Molecular Concentration and the PS tail length. On the other hand, the series of 2PS(n)-AC(60) remained in the state of bilayer vesicles in the same Concentration range. Combining both of the experimental results obtained in the low and high Molecular Concentrations, a systematic morphological phase diagram was constructed for the series of PS(n)-AC(60) with different PS tail lengths. The versatile and Concentration-sensitive phase behaviors of these Molecular shape amphiphiles are unique and have not been systematically explored in the traditional surfactants and block copolymers systems.