74 results on '"Dong-Po Song"'
Search Results
2. Self‐Assembly and In Situ Quaternization of Triblock Bottlebrush Block Copolymers via Organized Spontaneous Emulsification for Effective Loading of DNA
- Author
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Zhaoxu Wang, Qiujun Liu, Qian Liu, Hao Qi, Yuesheng Li, and Dong‐Po Song
- Subjects
Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2023
3. Hierarchical Assemblies of Bottlebrush/Homopolymer Blends: Tailoring Phase Interfacial Curvature for Tunable Photonics †
- Author
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Han Yi, Yuesheng Li, and Dong‐Po Song
- Subjects
General Chemistry - Published
- 2023
4. One-Step Synthesis of Sequence-Controlled Polyester-block-Poly(ester-alt-thioester) by Chemoselective Multicomponent Polymerization
- Author
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Xiao-Lu Chen, Bin Wang, Dong-Po Song, Li Pan, and Yue-Sheng Li
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Inorganic Chemistry ,Polymers and Plastics ,Organic Chemistry ,Materials Chemistry - Published
- 2022
5. Supersoft Elastic Bottlebrush Microspheres with Stimuli-Responsive Color-Changing Properties in Brine
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Ruijun Zhao, Yuesheng Li, Dong-Po Song, Xiaotong Li, Qiu-Jun Liu, and Bangbang Wang
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chemistry.chemical_classification ,Aqueous solution ,Materials science ,Polydimethylsiloxane ,technology, industry, and agriculture ,02 engineering and technology ,Surfaces and Interfaces ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Elastomer ,01 natural sciences ,Random coil ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Amphiphile ,Electrochemistry ,Copolymer ,Molecule ,General Materials Science ,0210 nano-technology ,Spectroscopy - Abstract
Solvent-free supersoft elastomer is highly desirable for building photonic structures with significant stimuli-responsive color changes. We report supersoft elastic porous microspheres with vivid structural colors obtained via self-assembly of amphiphilic bottlebrush block copolymers at the water/oil interface templated by ordered water-in-oil-in-water double emulsions. The porous structure is composed of cross-linked bottlebrush polydimethylsiloxane (PDMS) as the supersoft elastic skeleton and bottlebrush poly(ethylene oxide) (PEO) as the internal responsive layer. The obtained microspheres show large reversible volume changes through well-controlled dehydration or hydration of PEO in response to salt ions in an aqueous environment. As a result, full-spectrum colors are obtained dependent on different salt concentrations. In-situ observation of color reflection of a microsphere indicates a gradual structural transition from the outside to the inside corresponding to migration of water molecules and salt ions. Moreover, rod-like bottlebrush PEO exhibits an anion-induced salting-out behavior different from that of random coil polymers. The significantly responsive behaviors of bottlebrush block copolymer (BBCP) assemblies in the presence of salt ions primarily rely on the supersoft elastic skeleton of the porous structure, providing a facile route to the creation of stimuli-responsive photonic materials by low-cost self-assembly methods.
- Published
- 2021
6. Precise Tailoring of Polyester Bottlebrush Amphiphiles toward Eco‐Friendly Photonic Pigments via Interfacial Self‐Assembly
- Author
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Qilin Guo, Runze Xue, Jian Zhao, Yuxia Zhang, Gea T. van de Kerkhof, Kunyu Zhang, Yuesheng Li, Silvia Vignolini, and Dong‐Po Song
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Polymers ,Polyesters ,Water ,Emulsions ,General Chemistry ,General Medicine ,Hydrophobic and Hydrophilic Interactions ,Catalysis ,Polyethylene Glycols - Abstract
Biodegradable photonic microspheres with structural colors are promising substitutes to polluting microbeads and toxic dyes. Here, amphiphilic polyester-block-poly(ethylene glycol) bottlebrush block copolymers (BBCPs) with polylactic acid or poly(ϵ-caprolactone) as the hydrophobic block are synthesized and used to fabricate eco-friendly photonic pigments. Molecular parameters of BBCPs, including rigidity and symmetry, are precisely tailored by variation of side chain lengths, which enables effective manipulation of interfacial tension (γ). Organized spontaneous emulsion mechanism is enabled only when γ falls in a suitable range (10.6-14.3 mN m
- Published
- 2022
7. Discovery and Insights into Organized Spontaneous Emulsification via Interfacial Self-Assembly of Amphiphilic Bottlebrush Block Copolymers
- Author
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Yongfeng Men, Yuesheng Li, Xiao Yang, Xi Chen, and Dong-Po Song
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Materials science ,Polymers and Plastics ,Organic Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Chemical engineering ,Scientific method ,Amphiphile ,Materials Chemistry ,Copolymer ,Self-assembly ,0210 nano-technology ,Emulsion droplet - Abstract
Since the first discovery of spontaneous emulsification, the process has remained uncontrollable for centuries leading to unstable emulsion droplets with limited uses. Herein, by in situ observatio...
- Published
- 2021
8. Millisecond photothermal carbonization for in-situ fabrication of mesoporous graphitic carbon nanocomposite electrode films
- Author
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James J. Watkins, Yue Gai, Shengkai Li, Aditi Naik, Dong-Po Song, Yiliang Zhou, Huafeng Fei, Wenhao Li, and Janghoon Park
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chemistry.chemical_classification ,Fabrication ,Nanocomposite ,Materials science ,Carbonization ,Nanoparticle ,02 engineering and technology ,General Chemistry ,Polymer ,Photothermal therapy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Lithium-ion battery ,0104 chemical sciences ,chemistry ,Chemical engineering ,General Materials Science ,0210 nano-technology ,Mesoporous material - Abstract
Binder-free mesoporous graphitic carbon composite films on polymer or metal substrates are attractive for high-surface-area electrodes to achieve superior device performances. However, rapid and large-area fabrication of such materials remains a significant challenge due to the harsh conditions required for the carbonization process. We report an efficient method that combines bottom-up precursor film assembly with photothermal processing using sub-millisecond light pulses generated from a xenon flash lamp. This approach enables the rapid carbonization and graphitization of precursor films over large areas at ambient bulk temperature to yield functional films while avoiding damage to the substrates. The films contain light-absorbing nanoparticles to convert light energy into heat, a block copolymer to template the porous structures via self-assembly, and phenol-fomaldehyde resin to form the carbon skeleton. Graphitic carbon nanoribbons embedded in a porous carbon matrix are created under mild conditions using iron nanoparticles as the catalyst during the millisecond photothermal process. The resulting composite films show excellent electrochemical properties and are demonstrated for use as high capacity lithium ion battery anodes.
- Published
- 2021
9. Self-Assembled Photonic Microsensors with Strong Aggregation-Induced Emission for Ultra-Trace Quantitative Detection
- Author
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Qiu-Jun Liu, Dong-Po Song, Yuesheng Li, Yulian Li, Jing-Cheng Xu, and Hai-Feng Lu
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Analyte ,Materials science ,Polymers ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Homogeneous distribution ,Fluorescence ,Polyethylene Glycols ,Nitrophenol ,chemistry.chemical_compound ,Amphiphile ,Copolymer ,General Materials Science ,Aqueous solution ,General Engineering ,021001 nanoscience & nanotechnology ,Microspheres ,0104 chemical sciences ,Nanopore ,chemistry ,Chemical engineering ,Emulsions ,0210 nano-technology - Abstract
Ultratrace quantitative detection based on fluorescence is highly desirable for many important applications such as environmental monitoring or disease diagnosis, which however has remained a great challenge because of limited and irregular fluorescence responses to analytes at ultralow concentrations. Herein the problem is circumvented via local enrichment and detection of analytes within a microsensor, that is, photonic porous microspheres grafted with aggregation-induced emission gens (AIEgens). The obtained microspheres exhibit dual structural and molecular functions, namely, bright structural colors and strong fluorescence. Large fluorescence quenching induced by nitrophenol compounds in an aqueous environment is observed at ultralow concentrations (10-12-10-8 mol/L), enabling quantitative detection at a ppb level (ng/L). This is achieved within a porous structure with good connectivity between the nanopores to improve analyte diffusion, an internal layer of poly(ethylene oxide) (PEO) for analyte enrichment via hydrogen bonding, and homogeneous distribution of AIEgens within the PEO layer for enhanced fluorescence quenching. The fluorescent porous microspheres can be readily obtained in a single step templated by well-ordered water-in-oil-in-water double emulsion droplets with AIE amphiphilic bottlebrush block copolymers as the effective stabilizer.
- Published
- 2021
10. Supertough Poly(lactic acid) and Sustainable Elastomer Blends Compatibilized by PLLA-b-PMMA Block Copolymers as Effective A-b-C-Type Compatibilizers
- Author
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Juyang Liu, Dong-Po Song, Yingli Ding, Hai Jiang, Li Pan, Kunyu Zhang, Arun Alagarsamy, and Yuesheng Li
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General Chemical Engineering ,technology, industry, and agriculture ,macromolecular substances ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,Lactic acid ,chemistry.chemical_compound ,020401 chemical engineering ,chemistry ,Polymerization ,Polymer chemistry ,Copolymer ,0204 chemical engineering ,Methyl methacrylate ,0210 nano-technology - Abstract
A series of poly(L-lactic acid) (PLLA)-b-poly(methyl methacrylate) (PMMA) block copolymers with well-defined chemical structures were synthesized by ring-opening polymerization followed by atom-tra...
- Published
- 2020
11. Refractive Index Engineering as a Novel Strategy toward Highly Transparent and Tough Sustainable Polymer Blends
- Author
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Yang Zhang, Dong Huang, Si-Ting Sun, Yuesheng Li, Hang Wang, Dong-Po Song, Li Pan, Yingli Ding, and Kunyu Zhang
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chemistry.chemical_classification ,010407 polymers ,Toughness ,Materials science ,Polymers and Plastics ,Transparency (market) ,General Chemical Engineering ,Organic Chemistry ,Nanotechnology ,Izod impact strength test ,Polymer ,Elastomer ,01 natural sciences ,0104 chemical sciences ,Brittleness ,chemistry ,Polymer blend ,Refractive index - Abstract
High transparency and toughness are prerequisites for sustainable polymers if they are to find wide application as alternatives to petroleum-based polymers. However, the utility of sustainable polymers such as commercially available polylactide (PLA) is limited by their inherent brittleness and high cost. Unfortunately, toughening PLA-based materials via cost-effective blending strategies without sacrificing transparency remains a challenge. Herein, we report a novel strategy involving active refractive index matching for creation of highly transparent and tough PLA blends. Specifically, we engineered the refractive index of a promising renewable poly(epichlorohydrin-co-ethylene oxide) elastomer by introducing polar ionic moieties via a simple chemical method, and we blended the resulting ionomers with PLA. The best blend showed an impact strength of > 80 kJ/m2, an elongation at break of 400%, and high transparency (90%). These characteristics are of great importance for potential applications such as packaging. Our strategy offers a versatile new way to prepare high-performance sustainable polymer materials with excellent transparency.
- Published
- 2020
12. Janus Photonic Microspheres with Bridged Lamellar Structures via Droplet-Confined Block Copolymer Co-Assembly
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Qiujun Liu, Qilin Guo, Yulian Li, Dong-Po Song, and Yuesheng Li
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Materials science ,business.industry ,Nanotechnology ,General Medicine ,General Chemistry ,Catalysis ,Amphiphile ,Copolymer ,Lamellar structure ,Janus ,Self-assembly ,Photonics ,business ,Layer (electronics) ,Photonic crystal - Abstract
Artificial self-assembly systems typically exhibit limited capability in creating nature-inspired complex materials with advanced functionalities. Here, an effective co-assembly strategy is demonstrated for the facile creation of complex photonic structures with intriguing light reflections. Two different lipophilic and amphiphilic bottlebrush block copolymers (BCPs) are placed within shrinking droplets to enable a cooperative working mechanism of microphase segregation and organized spontaneous emulsification, respectively. Layer assemblies of the lipophilic BCP and uniform water nanodroplets stabilized by the bottlebrush surfactant are both generated, and co-assembled into a bridged lamellar structure with the alternating arrangement of layers and closely packed nanodroplet arrays. Janus microspheres with diverse dual optical characteristics are successfully fabricated, and reflected wavelengths of light are highly tunable simply by changing the formulation or molecular weight of BCP.
- Published
- 2021
13. Organic Lewis pairs for selective copolymerization of epoxides with anhydrides to access sequence-controlled block copolymers
- Author
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Yuesheng Li, Li Pan, Dong-Po Song, Bin Wang, and He-Yuan Ji
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Lactide ,Bicyclic molecule ,010405 organic chemistry ,Chemistry ,Succinic anhydride ,Regioselectivity ,010402 general chemistry ,01 natural sciences ,Pollution ,Combinatorial chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,Monomer ,Polymerization ,Organocatalysis ,Copolymer ,Environmental Chemistry - Abstract
Poly(ester-b-ether)s, a kind of meaningful and potentially bio-based block copolymer, are typically synthesized via ring-opening polymerization (ROP) of cyclic esters initiated by the pre-prepared polyether macroinitiator. However, a multi-step procedure is required in this traditional method. Herein, we detailed a one-step selective copolymerization process of mixed monomers to precisely prepare poly(ester-b-ether) block copolymers, which could minimize the additional catalytic processes and organic reagents of the multi-step procedure. The strategy enables ring-opening alternating copolymerization (ROAC) of anhydrides with epoxides and ROP of epoxides sequentially in a closed system. Organic Lewis pairs were utilized to catalyze the selective copolymerization and were easily removed from the reaction system which avoided the metal residues in the copolymers. Regioselective and living copolymerization is realized by using cooperative organocatalysts, yielding the poly(ester-b-ether) with a controlled monomer sequence, high isotacticity and predictable molecular weight (MW). The optimized organocatalysis exhibits broad monomer adaptability and allows fabricating structurally diverse poly(ester-b-ether)s. Epimerization was suppressed even when tricyclic and bicyclic anhydrides were used, which enables the synthesis of stereoregular block copolymers. Significantly, well-defined block copolymers based on renewable succinic anhydride were achieved. A tandem copolymerization is also performed by using lactide as an external trigger which could switch the selective copolymerization to lactide polymerization. The study provides a new route to the facile synthesis of poly(ester-b-ether) block copolymers using a metal-free catalytic system.
- Published
- 2019
14. Facile functionalization of isotactic polypropylene via click chemistry
- Author
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Yuesheng Li, Dong-Po Song, Li Pan, Zhe Ma, and Yulian Li
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Trimethylsilyl ,Comonomer ,Organic Chemistry ,Bioengineering ,02 engineering and technology ,Polymer ,Polyethylene glycol ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Tacticity ,Polymer chemistry ,Copolymer ,Click chemistry ,Surface modification ,0210 nano-technology - Abstract
We report here a new strategy for facile functionalization of isotactic polypropylene (iPP) via click chemistry. iPP bearing trimethylsilyl (TMS) protected alkynyl groups was prepared through copolymerization of propylene with a small amount of functional α-olefins with a zirconocene complex/AliBu3/[Ph3C][B(C6F5)4] catalytic system. The obtained copolymers exhibited high molecular weights beyond 2.0 × 105 and unimodal molecular distributions, with comonomer incorporation in the range of 1 to 4 mol% while maintaining good isotacticity ([mmmm] > 94%). Functionalization of the copolymers was achieved via TMS deprotection and click reactions in one-pot, providing a facile and efficient route to scalable fabrication of iPPs with diverse functionalities and improved physical properties. For instance, polyethylene glycol (PEG) was successfully grafted onto iPP polymer chains with a weight percentage up to 71.1%. Consequently, the hydrophilicity of the resultant copolymer was remarkably enhanced as revealed by the three times larger swelling of PEG-functionalized iPP after soaking in water for only a few minutes.
- Published
- 2019
15. Rapid Responsive Mechanochromic Photonic Pigments with Alternating Glassy-Rubbery Concentric Lamellar Nanostructures
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Yuesheng Li, Guiqiu Ma, Zhe Ma, Dong-Po Song, and Yun Dong
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Materials science ,Nanostructure ,business.industry ,fungi ,General Engineering ,food and beverages ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Compression (physics) ,01 natural sciences ,0104 chemical sciences ,Pigment ,visual_art ,visual_art.visual_art_medium ,Copolymer ,General Materials Science ,Lamellar structure ,Composite material ,Photonics ,0210 nano-technology ,business ,Structural coloration ,Photonic crystal - Abstract
Photonic pigment particles prepared via self-assembly have been suffering from their poor mechanical performances; i.e., they can easily be damaged and lose structural color under a compression for...
- Published
- 2021
16. Interfacial Self‐Assembly of Amphiphilic Core‐Shell Bottlebrush Block Copolymers Toward Responsive Photonic Balls Bearing Ionic Channels
- Author
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Tengfei Yuan, Yuesheng Li, and Dong‐Po Song
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Polymers and Plastics ,Polymers ,Organic Chemistry ,Materials Chemistry ,Polystyrenes ,Water ,Ion Channels ,Polyethylene Glycols - Abstract
Photonic balls can be facilely obtained through interfacial self-assembly of amphiphilic bottlebrush block polymers (BBCPs) within a water-in-oil-in-water (w/o/w) multiple emulsion system, and polystyrene (PS) has been employed as the skeleton of the balls showing no responsive properties. Here, the design and synthesis of core-shell BBCPs are demonstrated with a poly(tert-butyl acrylate)-block-polystyrene (PtBA-b-PS) block copolymer as the hydrophobic side chains and poly(ethylene glycol) as the hydrophilic block. Interfacial self-assembly of the core-shell BBCPs within shrinking droplets produces porous microspheres with full-spectrum structural colors through an organized spontaneous emulsification process. The PtBA core wrapped by PS in the skeleton of the balls can be converted into polyacrylic acid (PAA) forming an ionic channel responsive to pH variations. Consequently, the hydrolyzed photonic balls show different colors under different pH conditions dependent on varying degrees of ionization and hydration of the PAA channel. Reflected colors can be verified using an optical spectrometer, providing an effective strategy for precise pH indication.
- Published
- 2022
17. Oxidation Control of Bottlebrush Molecular Conformation for Producing Libraries of Photonic Structures
- Author
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Hong-Kun Geng, Yuesheng Li, Bin Wang, Zhe Ma, Yulian Li, Dong-Po Song, Li Pan, Yun Dong, Guiqiu Ma, and Xi Chen
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Fabrication ,Materials science ,business.industry ,010405 organic chemistry ,General Medicine ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical engineering ,Pulmonary surfactant ,Ferrocene ,chemistry ,Amphiphile ,Copolymer ,Photonics ,Porosity ,business ,Structural coloration - Abstract
Self-assembly is important for creating photonic structures and structural color is typically tunable by varying the size of building blocks, which are themselves obtained after time-consuming chemical syntheses. The molecular conformation of bottlebrush block copolymers (BBCPs) in solution can be manipulated to create libraries of photonic structures. Amphiphilic BBCPs bearing oxidation-responsive ferrocene groups on the hydrophilic block are used to fabricate porous particles via evaporation-induced self-assembly of water-in-oil-in-water (W/O/W) double emulsions stabilized by the BBCP surfactant. In situ oxidation of the ferrocene groups by hydrogen peroxide at the W/O interface leads to enhanced hydrophilicity, more hydration, and chain extension of the hydrophilic block. Consequently, larger internal water droplets are spontaneously formed, yielding larger pores within the microparticles. The pore diameter is readily tunable from 144 to 301 nm with a single BBCP, thereby generating full-spectrum structural colors. This work provides a straightforward method for fabrication of libraries of photonic pigments in an easy and scalable manner.
- Published
- 2020
18. Angular‐Independent Photonic Pigments via the Controlled Micellization of Amphiphilic Bottlebrush Block Copolymers
- Author
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Tianheng H. Zhao, Xi Chen, Dong-Po Song, Silvia Vignolini, Richard M. Parker, Gianni Jacucci, Zhao, Tianheng [0000-0002-2705-0329], Jacucci, Gianni [0000-0002-9156-0876], Song, Dong-Po [0000-0002-2825-4999], Vignolini, Silvia [0000-0003-0664-1418], Parker, Richard [0000-0002-4096-9161], and Apollo - University of Cambridge Repository
- Subjects
Materials science ,FOS: Physical sciences ,Nanotechnology ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,01 natural sciences ,Photonic metamaterial ,Amphiphile ,Copolymer ,General Materials Science ,chemistry.chemical_classification ,cond-mat.soft ,business.industry ,Mechanical Engineering ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,3. Good health ,Iridescence ,chemistry ,Mechanics of Materials ,Soft Condensed Matter (cond-mat.soft) ,physics.optics ,Photonics ,0210 nano-technology ,business ,Structural coloration ,Visible spectrum ,Optics (physics.optics) ,Physics - Optics - Abstract
Photonic materials with angular independent structural colour are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel controlled micellization self-assembly mechanism within emulsified toluene-in-water droplets. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally coloured pigments. Furthermore, the reflected colour can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290 kDa) by altering the initial emulsification conditions. Such photonic pigments have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves colour purity without the need for either refractive index matching or the inclusion of a broadband absorber., 32 pages, 18 figures, 1 table
- Published
- 2020
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19. Chiral Arrangements of Au Nanoparticles with Prescribed Handedness Templated by Helical Pores in Block Copolymer Films
- Author
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James J. Watkins, Alexander E. Ribbe, Dong-Po Song, and Xuemin Lu
- Subjects
Plasmonic nanoparticles ,Materials science ,Fabrication ,Polymers and Plastics ,Ethylene oxide ,Organic Chemistry ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Template ,chemistry ,Chemical engineering ,Materials Chemistry ,Copolymer ,0210 nano-technology - Abstract
Fabrication of films with plasmonic nanoparticles (NPs) arrays arranged in chiral configurations of prescribed handedness is highly attractive for the design of new functional materials; however, this remains a formidable challenge in nanotechnology. In this study, we demonstrated the controlled arrangements of gold (Au) NPs into helical structures templated by helical pores created in cross-linked block copolymer (BCP) films. d- and l-tartaric acid (TA) were used to direct the self-assembly of achiral poly(1,4-butadiene)-b-poly(ethylene oxide) BCPs into helical cylindrical morphologies with prescribed handedness, i.e., D or L. Helical pores were generated by BCP cross-linking followed by TA extraction. Helical Au NP arrays, subsequently arranged within the helical pores, exhibited the chiral optical response. The helical structures of NPs arrays and the resulting optical handedness were tunable simply by using either D- or L-porous templates. This simple strategy offers a straightforward pathway for the ...
- Published
- 2017
20. Polystyrene-block-poly(ethylene oxide) Bottlebrush Block Copolymer Morphology Transitions: Influence of Side Chain Length and Volume Fraction
- Author
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Yue Gai, James J. Watkins, Dong-Po Song, and Benjamin M. Yavitt
- Subjects
Materials science ,Polymers and Plastics ,Ethylene oxide ,Organic Chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry.chemical_compound ,chemistry ,Polymerization ,Polymer chemistry ,Volume fraction ,Materials Chemistry ,Side chain ,Copolymer ,Melting point ,Lamellar structure ,Polystyrene ,0210 nano-technology - Abstract
A systematic study was conducted to investigate the morphology transitions that occur in polystyrene-block-poly(ethylene oxide) (PS-b-PEO) bottlebrush block copolymers (BBCP) upon varying PEO volume fraction (fPEO) from 22% to 81%. A series of PS-b-PEO BBCPs with different PEO side chain lengths were prepared using ring-opening metathesis polymerization (ROMP) of PEO–norbornene (PEO-NB) (Mn ∼ 0.75, 2.0, or 5.0 kg/mol) and PS–norbornene (PS-NB) (Mn ∼ 3.5 kg/mol) macromonomers (MM). A map of fPEO versus side chain asymmetry (Mn(PEO-NB)/Mn(PS-NB)) was constructed to describe the BBCP phase behavior. Symmetric and asymmetric lamellar morphologies were observed in the BBCPs over an exceptionally wide range of fPEO from 28% to 72%. At high fPEO, crystallization of PEO was evident. Temperature-controlled SAXS and WAXS revealed the presence of high order reflections arising from phase segregation above the PEO melting point. A microphase transition temperature TMST was observed over a temperature range of 150–180...
- Published
- 2017
21. High Molecular Mobility and Viscoelasticity of Microphase-Separated Bottlebrush Diblock Copolymer Melts
- Author
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H. Henning Winter, James J. Watkins, Yue Gai, Dong-Po Song, and Benjamin M. Yavitt
- Subjects
Polymers and Plastics ,Ethylene oxide ,Small-angle X-ray scattering ,Scattering ,Organic Chemistry ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Viscoelasticity ,0104 chemical sciences ,Styrene ,law.invention ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Rheology ,Magazine ,law ,Polymer chemistry ,Materials Chemistry ,Copolymer ,0210 nano-technology - Abstract
We investigate the linear viscoelastic behavior of poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) AB diblock brush copolymer materials over a range of volume fractions and with side-chain lengths below entanglement molecular weight (PS Mn ∼ 3.5 kg/mol and PEO Mn ∼ 5 kg/mol). The high chain mobility of the brush architecture results in rapid microphase segregation of the brush copolymer segments, which occurred after mild thermal annealing. Master curves of the dynamic moduli were obtained by time–temperature superposition (tTS). The reduced degree of chain entanglements leads to a unique liquid-like rheology similar to that of bottlebrush (BB) homopolymers, even in the microphase-segregated state. The microphase-segregated domains were found to align at exceptionally low strain amplitudes (γ = 0.01) and mild processing temperatures as confirmed by small-angle X-ray scattering (SAXS). Domain/grain orientation occurred readily at strains within the linear viscoelastic regime (LVR) without noticeable ef...
- Published
- 2016
22. Thermal Analysis of Crystallization and Phase Transition in Novel Polyethylene Glycol Grafted Butene-1 Copolymers
- Author
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Yulian Li, Yuesheng Li, Yahui Lou, Chuanbin An, Bin Wang, Dong-Po Song, Li Pan, and Zhe Ma
- Subjects
Phase transition ,Materials science ,melting ,Polymers and Plastics ,long-chain graft ,technology, industry, and agriculture ,General Chemistry ,Polyethylene glycol ,Article ,law.invention ,lcsh:QD241-441 ,chemistry.chemical_compound ,Differential scanning calorimetry ,lcsh:Organic chemistry ,chemistry ,Chemical engineering ,law ,phase transition ,PEG ratio ,Copolymer ,Side chain ,butene-1 copolymer ,crystallization kinetics ,Crystallization ,Thermal analysis - Abstract
Copolymerization is an effective strategy to regulate the molecular structure and tune crystalline structures. In this work, novel butene-1 copolymers with different polyethylene glycol (PEG) grafts (number-average molecular weight Mn = 750, 2000, and 4000 g/mol) were synthesized, for the first time introducing long-chain grafts to the polybutene-1 main chain. For these PEG-grafted copolymers, crystallization, melting, and phase transition behaviors were explored using differential scanning calorimetry. With respect to the linear homopolymer, the incorporation of a trimethylsilyl group decreases the cooling crystallization temperature (Tc), whereas the presence of the long PEG grafts unexpectedly elevates Tc. For isothermal crystallization, a critical temperature was found at 70 °, C, below which all polyethylene glycol-grafted butene-1 (PB-PEG) copolymers have faster crystallization kinetics than polybutene-1 (PB). The subsequent melting process shows that for the identical crystallization temperature, generated PB-PEG crystallites always have lower melting temperatures than that of PB. Moreover, the II-I phase transition behavior of copolymers is also dependent on the length of PEG grafts. When form II, obtained from isothermal crystallization at 60 °, C, was annealed at 25 °, C, PB-PEG-750, with the shortest PEG grafts of Mn = 750 g/mol, could have the faster transition rate than PB. However, PB-PEG-750 exhibits a negative correlation between transition rate and crystallization temperature. Differently, in PB-PEG copolymers with PEG grafts Mn = 2000 and 4000 g/mol, transition rates rise with elevating crystallization temperature, which is similar with homopolymer PB. Therefore, the grafting of the PEG side chain provides the available method to tune phase transition without sacrificing crystallization capability in butene-1 copolymers.
- Published
- 2019
23. Hierarchical Photonic Pigments via the Confined Self-Assembly of Bottlebrush Block Copolymers
- Author
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Tianheng H. Zhao, Richard M. Parker, Dong-Po Song, Giulia Guidetti, Silvia Vignolini, Zhao, Tianheng [0000-0002-2705-0329], Guidetti, Giulia [0000-0002-6065-3359], Vignolini, Silvia [0000-0003-0664-1418], Parker, Richard [0000-0002-4096-9161], and Apollo - University of Cambridge Repository
- Subjects
Fabrication ,Materials science ,General Physics and Astronomy ,confined self-assembly ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Pigment ,Copolymer ,General Materials Science ,bottlebrush block copolymers ,Photonic crystal ,business.industry ,General Engineering ,structural colors ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,microspheres ,photonic crystals ,visual_art ,visual_art.visual_art_medium ,Self-assembly ,Photonics ,0210 nano-technology ,business ,Structural coloration ,Visible spectrum - Abstract
Hierarchical, structurally colored materials offer a wide variety of visual effects that cannot be achieved with standard pigments or dyes. However, their fabrication requires simultaneous control over multiple length-scales. Here we introduce a robust strategy for the fabrication of hierarchical photonic pigments via the confined self-assembly of bottlebrush block copolymers within emulsified microdroplets. The bottlebrush block copolymer self-assembles into highly ordered concentric lamellae, giving rise to a near perfect photonic multi-layer in the solid-state, with reflectivity up to 100%. The reflected color can be readily tuned across the whole visible spectrum by either altering the molecular weight or by blending the bottlebrush block copolymers. Furthermore, the developed photonic pigments are responsive, with a selective and reversible color change observed upon swelling in different solvents. Our system is particularly suited for the scalable production of photonic pigments, arising from their rapid self-assembly mechanism and size-independent color.
- Published
- 2019
24. Rapid, Large-Area Synthesis of Hierarchical Nanoporous Silica Hybrid Films on Flexible Substrates
- Author
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Aditi Naik, James J. Watkins, Dong-Po Song, Shengkai Li, and Alexander E. Ribbe
- Subjects
Nanoporous ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Photothermal therapy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Catalysis ,Silsesquioxane ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Colloidal gold ,Polyethylene terephthalate ,Copolymer ,Thin film ,0210 nano-technology ,Mesoporous material - Abstract
We report a simple strategy for the creation of large-area nanoporous hybrid films of silica, carbon, and gold on polyethylene terephthalate via photothermal processing. This method enables the selective heating of light-absorbing thin films on low-temperature substrates using sub-millisecond light pulses generated by a xenon flash lamp. The film contains gold nanoparticles as the nanoheaters to convert light energy to heat, a sacrificial block copolymer surfactant to generate mesopores, and cross-linked polyhedral oligomeric silsesquioxane as the silica source to form the skeleton of the porous structure. Hierarchical porous structures are achieved in the films after photothermal treatment, with uniform mesopores (44-48 nm) on the surface and interconnected macropores (50 nm) underneath resulting from a foaming effect during release of gaseous decomposition products. The loading of gold nanoparticles is up to 43 wt % in the product, with less than 2 wt % organic residue. This rapid and large-area process for the synthetis of porous structures is compatible with roll-to-roll manufacturing for the fabrication of flexible devices.
- Published
- 2016
25. Structural Diversity and Phase Behavior of Brush Block Copolymer Nanocomposites
- Author
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Alexander E. Ribbe, Dong-Po Song, Samuel P. Gido, Yue Gai, James J. Watkins, and Benjamin M. Yavitt
- Subjects
Acrylate ,Nanocomposite ,Materials science ,Polymers and Plastics ,Ethylene oxide ,Organic Chemistry ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanomaterials ,Inorganic Chemistry ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Phase (matter) ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Side chain ,0210 nano-technology - Abstract
Brush block copolymers (BBCPs) exhibit attractive features for use as templates for functional hybrid nanomaterials including rapid ordering dynamics and access to broad ranges of domain sizes; however, there are relatively few studies of the morphology of the BBCPs as a function of their structural variables and fewer still studies of BBCP composite systems. Here we report the structural diversity and phase behavior of one class of BBCP nanocomposites as a function of the volume fractions of their components and the side chain symmetry of the BBCPs. We conducted a systematic investigation of gold nanoparticle (NP) (∼2 nm) assembly in a series of poly(tert-butyl acrylate)-block-poly(ethylene oxide) (PtBA-b-PEO) BBCPs with a fixed side chain length of PtBA (Mn = 8.2 kg/mol) but with different PEO brush lengths (Mn = 5.0, 2.0, or 0.75 kg/mol) as well as volume fractions (fPEO = 0.200–0.484). The gold NPs are selectively incorporated within the PEO domain via hydrogen bond interactions between the 4-mercapto...
- Published
- 2016
26. Directed Assembly of Quantum Dots Using Brush Block Copolymers for Well-Ordered Nonlinear Optical Nanocomposites
- Author
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Wanting Xie, Dong-Po Song, Robert A. Norwood, Cheng Li, Soroush Mehravar, Shiva Shahin, James J. Watkins, Xiaohui Liu, and Jae-Hwang Lee
- Subjects
Nanocomposite ,Photoluminescence ,Materials science ,Polymers and Plastics ,Cadmium selenide ,business.industry ,Organic Chemistry ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Quantum dot ,Materials Chemistry ,Copolymer ,Optoelectronics ,Lamellar structure ,0210 nano-technology ,business ,Photonic crystal - Abstract
We report the directed assembly of quantum dots (QDs) within well-ordered photonic nanocomposites using a family of (polynorbornene-graft-poly(styrene))-block-(polynorbornene-graft-poly(ethylene oxide)) (PS-b-PEO) brush block copolymers (BBCPs). Cadmium selenide (CdSe) nanoparticles (NPs) modified with 11-mercaptoundecylhydroquinone are selectively incorporated within the PEO domains of the self-assembled BBCPs via strong hydrogen-bonding interactions between the ligands on QDs and PEO brushes of the BBCPs. Well-ordered QD arrays were readily created within a periodic lamellar polymer matrix, or one-dimensional photonic crystal, with a widely tunable lattice spacing ranging from 46.2 to up to 145 nm. The loading concentration of the QDs can be up to 30 wt % (15 vol %) while maintaining a well-ordered lamellar morphology, providing an optical gain material platform for the systematic investigation of optical properties. Strong photoluminescence and third harmonic generation from the well-ordered QD arrays ...
- Published
- 2016
27. Strong Ligand–Block Copolymer Interactions for Incorporation of Relatively Large Nanoparticles in Ordered Composites
- Author
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James J. Watkins, Dong-Po Song, Yue Gai, Benjamin M. Yavitt, and Ying Lin
- Subjects
Nanocomposite ,Materials science ,Polymers and Plastics ,Hydroquinone ,Ligand ,Organic Chemistry ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Colloidal gold ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Particle ,Phenol ,0210 nano-technology - Abstract
For well-ordered block copolymer (BCP) nanocomposites containing nanoparticles (NPs), the ratio of NP core diameter (dcore) and BCP domain width (L) has been generally limited with dcore/L < 0.3 when NP/BCP interactions are relatively neutral or weak. Here, we systematically investigate the spatial distribution of gold nanoparticles (NP) ranging in size up to 0.8 times that of the target domain width in symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) using a hydrogen-bonding-mediated (H-bonding) assembly. NPs with core diameters (dcore) 2, 5, 9, and 15 nm are coated with ligands bearing phenol groups as the hydrogen-donating sites for H-bonding including 2-(11-mercaptoundecyl)hydroquinone and thiol-terminated poly(4-hydroxystyrene). These hydroxylated NPs are selectively incorporated into the P2VP block (domain width L = 7–37 nm) over a wide range of volume fractions (ϕ = 3–26 vol %). Particle distributions are biased toward the center of in the P2VP domains when dcore/L is greater than 0.3 and ...
- Published
- 2016
28. Block Copolymer Nanocomposites with High Refractive Index Contrast for One-Step Photonics
- Author
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Dong-Po Song, Wenhao Li, Cheng Li, and James J. Watkins
- Subjects
Acrylate ,Nanocomposite ,Materials science ,High-refractive-index polymer ,General Engineering ,General Physics and Astronomy ,Nanoparticle ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Polymer chemistry ,Copolymer ,Refractive index contrast ,General Materials Science ,0210 nano-technology ,Refractive index ,Photonic crystal - Abstract
Photonic crystals (PhCs) prepared using the self-assembly of block copolymers (BCPs) offer the potential for simple and rapid device fabrication but typically suffer from low refractive index contrast (Δn ≤ 0.1) between the phase-segregated domains. Here, we report the simple fabrication of BCP-based photonic nanocomposites with large differences in refractive index (Δn0.27). Zirconium oxide (ZrO2) nanoparticles coated with gallic acid are used to tune the optical constants of the target domains of self-assembled (polynorbornene-graft-poly(tert-butyl acrylate))-block-(polynorbornene-graft-poly(ethylene oxide)) (PtBA-b-PEO) brush block copolymers (BBCPs). Strong hydrogen-bonding interactions between the ligands on ZrO2 and PEO brushes of the BBCPs enable selective incorporation and high loading of up to 70 wt % (42 vol %) of the ZrO2 nanoparticles within the PEO domain, resulting in a significant increase of refractive index from 1.45 to up to 1.70. Consequently, greatly enhanced reflection at approximately 398 nm (increases of ∼250%) was observed for the photonic nanocomposites (domain spacing = 137 nm) relative to that of the unmodified BBCPs, which is consistent with numeric modeling results using transfer matrix methods. This work provides a simple strategy for a wide range tuning of optical constants of BCP domains, thereby enabling the design and creation of high-performance photonic coatings for various applications. The large refractive index contrast enables high reflectivity while simultaneously reducing the coating thickness necessary, compared to pure BCP systems.
- Published
- 2016
29. Neutral Nickel Catalysts for Olefin Homo- and Copolymerization: Relationships between Catalyst Structures and Catalytic Properties
- Author
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Hongliang Mu, Li Pan, Dong-Po Song, and Yuesheng Li
- Subjects
Nickel ,Olefin fiber ,Chemistry ,Copolymer ,chemistry.chemical_element ,Organic chemistry ,General Chemistry ,Post-metallocene catalyst ,Catalysis - Published
- 2015
30. Optimization of media components and culture conditions for polyhydroxyalkanoates production by Bacillus megaterium
- Author
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R. Guru Raj Rao, K. Mohanrasu, Dong-Po Song, G.H. Dinesh, Kunyu Zhang, Jeyaraman Jeyakanthan, G. Siva Prakash, Sudhakar Muniyasamy, Arivalagan Pugazhendhi, and A. Arun
- Subjects
Chromatography ,biology ,020209 energy ,General Chemical Engineering ,Organic Chemistry ,technology, industry, and agriculture ,Energy Engineering and Power Technology ,Potassium nitrate ,macromolecular substances ,02 engineering and technology ,biology.organism_classification ,Polyhydroxyalkanoates ,Lactic acid ,Polyhydroxybutyrate ,chemistry.chemical_compound ,Fuel Technology ,020401 chemical engineering ,chemistry ,0202 electrical engineering, electronic engineering, information engineering ,Urea ,lipids (amino acids, peptides, and proteins) ,Ammonium ,Ammonium chloride ,0204 chemical engineering ,Bacillus megaterium - Abstract
Polyhydroxybutyrate (PHB) accumulating Bacillus megaterium was isolated from marine water. To increase the PHB productivity by Bacillus megaterium, steps were taken to evaluate the effects of carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch and sucrose at a level of 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at a level of 2 g/L) and different pH. A maximum yield of 2.74 g/L of PHB was achieved for glucose as the carbon source and ammonium sulphate as the nitrogen source at pH 7. The optimized conditions were further used for batch fermentation throughout 72 h. Significantly maximum PHB of 5.61 g/L was obtained in a laboratory scale bioreactor at 64 h. The extracted polymer was compared with the authentic PHB and was confirmed to be PHB using FTIR, 1H NMR, DSC and TGA analysis, respectively.
- Published
- 2020
31. Ligand Steric and Electronic Effects on β-Ketiminato Neutral Nickel(II) Olefin Polymerization Catalysts
- Author
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Dong-Po Song, Yong-Xia Wang, Yue-Sheng Li, Ji-Xing Yang, and Xin-Cui Shi
- Subjects
Steric effects ,Ligand ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Branching (polymer chemistry) ,Medicinal chemistry ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Nickel ,chemistry ,Pyridine ,Electronic effect ,Physical and Theoretical Chemistry ,Phosphine - Abstract
A series of novel neutral nickel complexes 3a-g and 4a-d bearing the beta-ketiminato ligands [(2,6-(Pr2C6H3)-Pr-i)N=CHCHC(R)O]Ni(R')(L) (for 3a-g, R' = Me, L = Py, and R = Bu-t (3a), Ph (3b), 1-naphthyl (3c), 9-anthryl (3d), PhNMe2(p) (3e), PhOMe(p) (3f), PhCF3(p) (3g); for 4a-d, R' = Ph, L = PPh3, and Bu-t (4a), Ph (4b), 1-naphthyl (4c), 9-anthryl (4d)) have been synthesized and characterized. The molecular structures of 3b-d,f,g and 4a,c were further confirmed by X-ray crystallographic analysis. These complexes were employed in ethylene polymerization to systematically investigate ligand steric and electronic effects on the catalytic properties, including activity, molecular weight (MW), and branching number of the polyethylene obtained. The complexes bearing more bulky ligands showed higher activities and produced more branched polyethylene. Electron-deficient ligands were found to increase the catalytic activity, decrease the MW, and enhance the branching content of the polyethylene. In addition, phosphine Ni-II-Ph complexes 4a-d proved to be more active than the corresponding pyridine Ni-II-Me complexes 3a-d, probably due to the easier dissociation of PPh3 relative to a pyridine from a nickel center.
- Published
- 2012
32. Functionalization of vinylic addition polynorbornenes via efficient copolymerization of norbornene using Ni(II)-Me complexes
- Author
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Hongliang Mu, Yue-Sheng Li, Dong-Po Song, Yan-Guo Li, and Xin-Cui Shi
- Subjects
chemistry.chemical_classification ,Polymers and Plastics ,Ligand ,Chemistry ,Organic Chemistry ,Catalysis ,chemistry.chemical_compound ,Monomer ,Pyridine ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Addition polymer ,Alkyl ,Norbornene - Abstract
The facile and efficient functionalization of polynorbornene has been achieved through direct copolymerization of norbornene (NB) with 5-norbornene-2-yl acetate (NBA) or 5-norbornene-2-methanol (NBM) using a series of beta-ketiminato Ni(II)-Me pyridine complexes 14 (Scheme 2) in the presence of B(C6F5)3. Remarkably, the monomer conversion could reach up to about 96% in 10 min in the NB/NBA copolymerization. The copolymers with wide NBA contents (3.338.4 mol %) were obtained by variation of reaction conditions. These copolymers have high molecular weights (MWs) (Mn = 41.8144 kg/mol) and narrow MW distributions (Mw/Mn = 1.802.27). In the absence of alkyl aluminum compounds, a monomer conversion of 81% was observed in the NB/NBM copolymerization, and copolymers with NBM content in the range of 11.221.8 mol % were obtained by variation of reaction conditions. In addition, Ni(II)-Me pyridine complexes 2 was very active at a low B/Ni molar ratio of 6, while bis-ligand complex 6 bearing the same ligand just showed moderate efficiency at a high B/Ni molar ratio of 20. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 562-570, 2012
- Published
- 2011
33. Observations and Mechanistic Insights on Unusual Stability of Neutral Nickel Complexes with a Sterically Crowded Metal Center
- Author
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Dong-Po Song, Bai-Xiang Li, Hongliang Mu, Yong-Xia Wang, and Yue-Sheng Li
- Subjects
Steric effects ,Chemistry ,Ligand ,Stereochemistry ,Organic Chemistry ,chemistry.chemical_element ,Chain termination ,Medicinal chemistry ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Nickel ,Polymerization ,Pyridine ,Phenyl group ,Physical and Theoretical Chemistry - Abstract
A series of novel nickel(II) methyl pyridine complexes based on beta-ketiminato and phenoxyiminato ligands, [(2,6-(i)Pr(2)C(6)H(3))N=CH(8-R(1)C(10)H(7))O]Ni(Me)(Py) (5a, R(1) = phenyl; 5b, R(1) = norbornyl), [(2,6-(i)Pr(2)C(6)H(3))N=CH(8-R(1)C(10)H(5))O]Ni(Me)(Py) (6a, R(1) = phenyl; 6b, R(1) = norbornyl), and [(2,6-(i)Pr(2)C(6)H(3))N=CHCHC(2'-R(2)C(6)H(4))O]Ni(Me)(Py) (7a, R(2) = H; 7b, R(2) = phenyl), have been synthesized and characterized. Molecular structures of 5a and 6b were further confirmed by X-ray crystallographic analysis. These complexes showed very different catalytic properties for ethylene polymerization. Design and construction of a special catalyst structure like 5a with a phenyl group directed toward the nickel(II) center proved to be an effective strategy for improving catalyst stability. Remarkably, according to (1)H NMR spectroscopy, bis-ligated deactivation of complex 5a was entirely avoided, while a rapid deactivation rate was observed with regard to the parent complex C without a phenyl group in the R(1) position. As a result, higher activities of complex 5a were obtained relative to complex C under the same polymerization conditions. In addition, the ligand backbone was found to have a great influence on polymerization behaviors. Specifically, the polyethylenes with greatly decreased molecular weights were produced by neutral nickel phenoxyiminato catalysts 6a,b in comparison with values for the corresponding beta-ketiminato catalysts 5a,b. This is best explained by DFT results that the ethylene insertion and chain termination barriers for complex 6a are very different from those of complex 5a.
- Published
- 2011
34. Highly Active Single-Component Neutral Nickel Ethylene Polymerization Catalysts: The Influence of Electronic Effects and Spectator Ligands
- Author
-
Hongliang Mu, Wei-Ping Ye, Dong-Po Song, and Yue-Sheng Li
- Subjects
Steric effects ,chemistry.chemical_classification ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Polymer ,Carbon-13 NMR ,Medicinal chemistry ,Catalysis ,Inorganic Chemistry ,Nickel ,chemistry.chemical_compound ,chemistry ,Pyridine ,Electronic effect ,Proton NMR ,Physical and Theoretical Chemistry - Abstract
A series of neutral nickel complexes [6-CHN(2,6-iPr2C6H3)-2-(2-NO2C6H4)-C6H3O-κ2- N,O]Ni(Ph)(PPh3) (6a), [6-CHN(2,6-iPr2C6H3)-2-(C6F5)-C6H3O-κ2-N,O]Ni(R)(L) (R = Ph, L = PPh3 (6b-PPh3); R = Me, L = pyridine (6b-Py); R = CH2Ph, L = PMe3 (6b-1Bz); R = η3-CH2Ph (6b-3Bz)), and [6-CHN(2,6-iPr2C6H3)-2-(2-OCH3C6H4)-C6H3O-κ2-N,O]Ni(Ph)(PPh3) (6c) based on 2-nitrophenyl-, pentafluorophenyl-, and 2-methoxyphenyl-substituted salicylaldimine ligands, respectively, have been synthesized and characterized by 1H NMR, 13C NMR, and elemental analysis. The solid structures of 6a, 6b-PPh3, 6b-Py, and 6b-1Bz have been further confirmed by X-ray crystallography. By combining the benefits of both electronic and steric factors, all the complexes with electron-withdrawing groups proved to be highly active single-component catalysts for ethylene polymerization, producing polymer with moderate molecular weights. Among these catalysts, 6b-PPh3 exhibited very high productivity of up to 5.87 × 106 g PE/molNi·h under optimal condition...
- Published
- 2010
35. Accessible, Highly Active Single-Component β-Ketiminato Neutral Nickel(II) Catalysts for Ethylene Polymerization
- Author
-
Wei-Ping Ye, Hongliang Mu, Yue-Sheng Li, Ji-Qian Wu, and Dong-Po Song
- Subjects
Single component ,Organic Chemistry ,Enthalpy ,Substituent ,chemistry.chemical_element ,Catalysis ,Inorganic Chemistry ,Nickel ,chemistry.chemical_compound ,Oxygen atom ,chemistry ,Ethylene polymerization ,Polymer chemistry ,Physical and Theoretical Chemistry ,Catalytic efficiency - Abstract
A series of novel neutral nickel complexes based on cyclic β-ketiminato ligands, [(2,6-iPr2C6H3)N═CHC6H8O]Ni(Ph)(PPh3) (3b), [(2,6-iPr2C6H3)N═CHCn+3H2n+2O(C6H4)]Ni(Ph)(PPh3) (6a−c), and [(2,6-iPr2C6H3)N═CHCn+3H2n+2O(C6H4)]Ni(CH3)(Py) (7a−c: a, n = 0; b, n = 1; c, n = 2) have been synthesized and characterized. These conveniently accessible complexes proved to be highly active catalysts for ethylene polymerization without an activator. Under the optimized conditions, an activity of 71.4 kg of PE/((mol of Ni) h atm) was observed using 6c as a catalyst. Particularly, it is of great interest that a bulky substituent proximate to the oxygen atom of the β-ketiminato complex is no longer a prerequisite to attain high catalytic efficiency, which is much different from the case for salicylaldiminato neutral nickel catalysts. This is effectively supported by the lower activation enthalpy changes of complexes 3b and 6a−c relative to values for the classic salicylaldiminato complexes. Moreover, for complexes 6a−c and...
- Published
- 2010
36. Facile, efficient functionalization of polyethylene via regioselective copolymerization of ethylene with cyclic dienes
- Author
-
Yue-Sheng Li, Miao Hong, Li Pan, Dong-Po Song, and Wei-Ping Ye
- Subjects
chemistry.chemical_classification ,Ethylene ,Polymers and Plastics ,Double bond ,Organic Chemistry ,Methylaluminoxane ,Epoxide ,Polyethylene ,chemistry.chemical_compound ,chemistry ,Dicyclopentadiene ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Norbornene - Abstract
The copolymerizations of ethylene with cyclic dienes [dicyclopentadiene (DCPD) and 2,5-norbornadiene (NBD(] using bis(beta-enaminoketonato)titanium complexes [PhN = C(R-2)CHC(R-1)O](2)TiCl2 (1a: R-1 = CF3, R-2 = CH3; 1b: R-1 = t-Bu, R-2 = CF3; 1c: R-1 = Ph, R-2 = CF3) have been investigated. In the presence of modified methylaluminoxane, these complexes exhibited high catalytic activities in the copolymerization of ethylene with DCPD or NBD, affording high molecular weight copolymers with unimodal molecular weight distributions. H-1 and C-13-NMR spectra reveal ethylene/DCPD copolymerizations by catalysts la c proceeds through the enchainment of norbornene ring. Catalysts la and 1c showed a tendency to afford alternating copolymers. More noticeably, catalysts 1b and 1c bearing bulky substituents on the ligands promote ethylene/NBD copolymerization without crosslinking, affording the copolymer containing intracyclic double bonds. The NBD incorporation as high as 27.2 mol % has been achieved by catalyst 1c. Moreover, the microstructures of the copolymers were further confirmed by the measurement of reactivity ratios and dyad monomer sequences as well as mean sequence lengths. The intracyclic double bonds of ethylene/DCPD or ethylene/NBD copolymers can be fully converted into polar groups such as epoxy, amine, silane, and hydroxyl groups under mild conditions. Convenient synthesis of hydroxylated polyethylene can be provided for the first time through the ring opening reaction of epoxide. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1764-1772, 2010
- Published
- 2010
37. Highly Active Neutral Nickel(II) Catalysts for Ethylene Polymerization Bearing Modified β-Ketoiminato Ligands
- Author
-
Wei-Ping Ye, Yue-Sheng Li, Yong-Xia Wang, Dong-Po Song, and Jing-yao Liu
- Subjects
Ethylene ,Ligand ,Organic Chemistry ,chemistry.chemical_element ,Emulsion polymerization ,Polyethylene ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Nickel ,chemistry ,Polymerization ,Polymer chemistry ,Physical and Theoretical Chemistry ,Carbon - Abstract
A series of novel neutral nickel complexes 4a−e bearing modified β-ketoiminato ligands [(2,6-iPr2C6H3)N═C(R1)CHC(2′-R2C6H4)O]Ni(Ph)(PPh3) (4a, R1 = R2 = H; 4b, R1 = H, R2 = Ph; 4c, R1 = H, R2 = Naphth; 4d, R1 = CH3, R2 = Ph; 4e, R1 = CF3, R2 = Ph) have been synthesized and characterized. Molecular structures of 4b and 4e were further confirmed by X-ray crystallographic analysis. Activated with B(C6F5)3, all the complexes are active for the polymerization of ethylene to branched polyethylenes. Ligand structure, i.e., substituents R1 and R2, greatly influences not only catalytic activity but also the molecular weight and branch content of the polyethylene produced. The phenyl-substituted complex 4b exhibits the highest activity of up to 145 kg PE/molNi·h·atm under optimized conditions, which is about 10 times more than unsubstituted complex 4a (14.0 kg PE/molNi·h·atm). Highly branched polyethylene with 103 branches per 1000 carbon atoms has been prepared using catalyst 4e.
- Published
- 2009
38. Synthesis and characterization of novel neutral nickel complexes bearing fluorinated salicylaldiminato ligands and their catalytic behavior for vinylic polymerization of norbornene
- Author
-
Ning-Hai Hu, Yan-Guo Li, Dong-Po Song, Yue-Sheng Li, and Ran Lu
- Subjects
Methylaluminoxane ,chemistry.chemical_element ,General Chemistry ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Nickel ,chemistry ,Polymerization ,Polymer chemistry ,Copolymer ,Electronic effect ,Addition polymer ,Norbornene - Abstract
A series of salicylaldimine-based neutral Ni(II) complexes (3a-j) [ArN = CH(C6H40)]Ni(PPh3)Ph [3a,Ar = C6H5; 3b,Ar = C6H4F(o); 3c, Ar = C6H4F(m); 3d, Ar = C6H4F(p); 3e, Ar = C6H3F2(2,4); 3f, Ar = C6H3F2(2,5); 3g, Ar = C6H3F2(2,6); 3h, Ar = C6H3F2(3,5); 3i, Ar = C6H2F3(3,4,5); 3j, Ar = C6H5] have been synthesized in good yield, and the structures of complexes 3a and 3i have been confirmed by X-ray crystallographic analysis. Using modified methylaluminoxane as a cocatalyst, these neutral Ni(II) complexes exhibited high catalytic activities for the vinylic polymerization of norbornene.
- Published
- 2008
39. Large-Volume Self-Organization of Polymer/Nanoparticle Hybrids with Millimeter-Scale Grain Sizes Using Brush Block Copolymers
- Author
-
Shengkai Li, Nicholas S. Colella, Jae-Hwang Lee, James J. Watkins, Cheng Li, Dong-Po Song, Xuemin Lu, Wanting Xie, and Samuel P. Gido
- Subjects
Scale (ratio) ,Chemistry ,Brush ,Nanoparticle ,Nanotechnology ,General Chemistry ,Biochemistry ,Catalysis ,law.invention ,Colloid and Surface Chemistry ,Volume (thermodynamics) ,law ,Copolymer ,Millimeter ,Nanometre ,Hybrid material - Abstract
We report that an exceptionally large volume of highly ordered arrays (single grains) on the order of millimeters in scale can be rapidly created through a unique innate guiding mechanism of brush block copolymers (BBCPs). The grain volume is over 10(9) times larger than that of typical self-assembled linear BCPs (LBCPs). The use of strong interactions between nanoparticles (NPs) and BBCPs enables high loadings of functional materials, up to 76 wt % (46 vol %) in the target domain, while maintaining excellent long-range order. Overall, this work provides a simple method to precisely control the spatial orientation of functionalities at nanometer length scales over macroscopic volumes, thereby enabling the production of hybrid materials for many important applications.
- Published
- 2015
40. Controlled supramolecular self-assembly of large nanoparticles in amphiphilic brush block copolymers
- Author
-
James J. Watkins, Yue Gai, Cheng Li, Dong-Po Song, Samuel P. Gido, Xiaohui Liu, Nicholas S. Colella, and Ying Lin
- Subjects
Ethylene oxide ,Chemistry ,Supramolecular chemistry ,Nanoparticle ,General Chemistry ,Biochemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Polymer chemistry ,Amphiphile ,Side chain ,Copolymer ,Self-assembly ,Hybrid material - Abstract
To date the self-assembly of ordered metal nanoparticle (NP)/block copolymer hybrid materials has been limited to NPs with core diameters (D(core)) of less than 10 nm, which represents only a very small fraction of NPs with attractive size-dependent physical properties. Here this limitation has been circumvented using amphiphilic brush block copolymers as templates for the self-assembly of ordered, periodic hybrid materials containing large NPs beyond 10 nm. Gold NPs (D(core) = 15.8 ± 1.3 nm) bearing poly(4-vinylphenol) ligands were selectively incorporated within the hydrophilic domains of a phase-separated (polynorbornene-g-polystyrene)-b-(polynorbornene-g-poly(ethylene oxide)) copolymer via hydrogen bonding between the phenol groups on gold and the PEO side chains of the brush block copolymer. Well-ordered NP arrays with an inverse cylindrical morphology were readily generated through an NP-driven order-order transition of the brush block copolymer.
- Published
- 2015
41. Hierarchical Photonic Pigments via the Confined Self-Assembly of Bottlebrush Block Copolymers.
- Author
-
Dong-Po Song, Zhao, Tianheng H., Guidetti, Giulia, Vignolini, Silvia, and Parker, Richard M.
- Published
- 2019
- Full Text
- View/download PDF
42. Synthesis and controlled self-assembly of UV-responsive gold nanoparticles in block copolymer templates
- Author
-
Dong-Po Song, Ying Lin, James J. Watkins, and Xinyu Wang
- Subjects
chemistry.chemical_compound ,Acrylate ,Template ,chemistry ,Colloidal gold ,Uv responsive ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Self-assembly ,Physical and Theoretical Chemistry ,Surfaces, Coatings and Films ,Styrene - Abstract
We demonstrate the facile synthesis of gold nanoparticles (GNPs) functionalized by UV-responsive block copolymer ligands, poly(styrene)-b-poly(o-nitrobenzene acrylate)-SH (PS-b-PNBA-SH), followed by their targeted distribution within a lamellae-forming poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer. The multilayer, micelle-like structure of the GNPs consists of a gold core, an inner PNBA layer, and an outer PS layer. The UV-sensitive PNBA segment can be deprotected into a layer containing poly(acrylic acid) (PAA) when exposed to UV light at 365 nm, which enables the simple and precise tuning of GNP surface properties from hydrophobic to amphiphilic. The GNPs bearing ligands of different chemical compositions were successfully and selectively incorporated into the PS-b-P2VP block copolymer, and UV light showed a profound influence on the spatial distributions of GNPs. Prior to UV exposure, GNPs partition along the interfaces of PS and P2VP domains, while the UV-treated GNPs are incorporated into P2VP domains as a result of hydrogen bond interactions between PAA on the gold surface and P2VP domains. This provides an easy way of controlling the arrangement of nanoparticles in polymer matrices by tailoring the nanoparticle surface using UV light.
- Published
- 2014
43. Photonic Resins: Designing Optical Appearance via Block Copolymer Self-Assembly.
- Author
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Dong-Po Song, Jacucci, Gianni, Dundar, Feyza, Naik, Aditi, Hua-Feng Fei, Vignolini, Silvia, and Watkins, James J.
- Subjects
- *
PHOTONIC crystal manufacturing , *MOLECULAR self-assembly , *BLOCK copolymers , *CHEMICAL synthesis - Abstract
Despite a huge variety of methodologies having been proposed to produce photonic structures by self-assembly, the lack of an effective fabrication approach has hindered their practical uses. These approaches are typically limited by the poor control in both optical and mechanical properties. Here we report photonic thermosetting polymeric resins obtained through brush block copolymer (BBCP) self-assembly. We demonstrate that the control of the interplay between order and disorder in the obtained photonic structure offers a powerful tool box for designing the optical appearance of the polymer resins in terms of reflected wavelength and scattering properties. The obtained materials exhibit excellent mechanical properties with hardness up to 172 MPa and Young's modulus over 2.9 GPa, indicating great potential for practical uses as photonic coatings on a variety of surfaces. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
44. [Autoimmune disorders affect the in vitro fertilization outcome in infertile women]
- Author
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Shu-Hua, Zou, Zong-Zhi, Yang, Peng, Zhang, Dong-Po, Song, Bo, Li, Rui-Ying, Wu, and Xue, Cong
- Subjects
Adult ,Pregnancy ,Pregnancy Outcome ,Humans ,Female ,Fertilization in Vitro ,Infertility, Female ,Autoantibodies ,Autoimmune Diseases - Abstract
To analyze the effect of autoimmune disorders on the outcome of in vitro fertilization and embryo transfer (IVF-ET) in infertile women.A total of 236 infertile women underwent IVF-ET, including 34 with antiphospholipid antibody (APA) positive, 33 anti-trophoblast antibody (ATA) positive, 35 anti-hCG antibody (hCGAb) positive, 32 anti-endometrium antibody (EmAb) positive, and 102 with antibodies negative that comprised the control group. Those with two or more antibodies positive were excluded in this study. Comparisons were made in the rates of embryo implantation, clinical pregnancy, miscarriage and biochemical pregnancy between the positive groups and the negative controls.There were no significant differences in the rates of embryo implantation and clinical pregnancy between the positive and negative groups (P0.05). The rate of biochemical pregnancy was higher in the APA, ATA and hCGAb positive than in the EmAb positive and the control group (P0.05). The miscarriage rate was higher while the ongoing pregnancy rate was lower in the positive groups than in the negative control (P0.05).Such autoantibodies as APA, ATA, HCG-Ab and EmAb may cause miscarriage in infertile women undergoing IVF and consequently reduce the rate of ongoing pregnancy, which necessitates the determination of these antibodies in these patients.
- Published
- 2008
45. Impact of antiovarian antibodies (AOA) on ovarian responsiveness in vitro fertilization and embryo transfer
- Author
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Shu-Hua, Zou, Peng, Zhang, Dong-Po, Song, Bo, Li, and Rui-Ying, Wu
- Subjects
Adult ,Ovulation ,Young Adult ,Reproductive Techniques, Assisted ,Ovary ,Humans ,Female ,Fertilization in Vitro ,Follicle Stimulating Hormone ,Embryo Transfer ,Infertility, Female ,Autoantibodies - Abstract
This study was to investigate the effects of antiovarian antibodies (AOA) on ovarian responsiveness in vitro fertilization and embryo transfer (IVF/ET).233 infertility women younger than 36 years undergone IVF/ET because of single salpingemphraxis were attended in the study, whose fast blood was taken to detect serum AOA by ELISA. Among them there were 35 women with serum AOA positive composed the study group and the other with serum AOA negative composed the control. Ovarian volume, antral follicle number, basal FSH, gonadotropin dosage and recollected oocytes were compared between the 2 groups.There's no difference in ovarian volume between serum AOA positive group with negative group, P0.05. The number of antral follicles was less and basal FSH was higher in AOA positive group than in control, P0.05; what's more, the ampoules of gonadotrophin consumed in AOA positive group exceed significantly in control, and less recollected oocytes in AOA positive group than in control, P0.01. Of the 233 infertility women, the serum AOA positive rate was 73.08% in the women who got less than 5 recollected oocytes, significantly higher than the other women in the study, P0.01.The existing of anti-ovarian antibodies had suppressive effects on the ovarian responsiveness in ovarian stimulation in IVF/ET cycle and on ovarian function. AOA should be detected before IVF/ET to evaluate ovarian responsiveness and further treatment seems necessary.
- Published
- 2008
46. Clockwise Helical Stacking of Triphenylbenzene-Based Organogelator Induced by Peripheral Chirality
- Author
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Yingying Zhao, Guofa Liu, Zhiguang Song, Ran Lu, Chunyan Bao, Xinchun Yang, Dong-Po Song, Tinghua Xu, and Ming Jin
- Subjects
Hexagonal crystal system ,organic chemicals ,Organic Chemistry ,Stacking ,General Medicine ,Biochemistry ,Fluorescence ,chemistry.chemical_compound ,Crystallography ,Monomer ,chemistry ,Phase (matter) ,Drug Discovery ,Molecule ,Self-assembly ,Clockwise ,Chirality (chemistry) - Abstract
We report on the synthesis and self-assembly of a new discotic organogelator based on π-conjugated triphenylbenzene with three peripheral chiral substituents. It is found that the introduction of chiral groups to the C3-symmetric molecule led to a hexagonal columnar chiral stacking of the molecules in a clockwise direction in the organogel fibers. And the fluorescent emission of the gel decreased significantly compared to the monomer state at the same concentration, as a result of the aggregation of the nonplanar triphenylbenzene core in the gel phase.
- Published
- 2007
47. Synthesis and self-assembly of dichalcone substituted carbazole-based low-molecular mass organogel
- Author
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Yingying Zhao, Dong-Po Song, Chunyan Bao, Tinghua Xu, Changhui Tan, Tongshun Shi, Yulan Chen, Lihong Su, and Ran Lu
- Subjects
Molecular mass ,Carbazole ,Organic Chemistry ,Fluorescent spectra ,Biochemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Transmission electron microscopy ,Organic chemistry ,Molecule ,Lamellar structure ,Self-assembly ,Physical and Theoretical Chemistry - Abstract
We report the synthesis and self-assembly of a new pi-conjugated dichalcone substituted carbazole-based low molecular mass organogelator. It could form stable gels in most halogen-aromatic solvents. The transmission electron microscopy (TEM) images revealed that the gel formed fibrous structures with diameter of 50-100 nm, which consisted of several thinner fibers. The FT-IR, UV-vis and XRD results suggested that the H-bonds and pi-pi interactions were the main driving forces for the formation of the self-assembled gel, in which the U-shaped molecules were stacked into lamellar structures. The fluorescent spectra showed that the emission of the xerogel red-shifted markedly compared with the sol state, which resulted from the aggregation of the molecules.
- Published
- 2006
48. Chiral Arrangements of Au Nanoparticles with Prescribed Handedness Templated by Helical Pores in Block Copolymer Films.
- Author
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Xuemin Lu, Dong-po Song, Ribbe, Alexander, and Watkins, James J.
- Subjects
- *
BLOCK copolymers , *POLYMER films , *GOLD nanoparticles , *NANOTECHNOLOGY , *TARTARIC acid , *MOLECULAR self-assembly - Abstract
Fabrication of films with plasmonic nanoparticles (NPs) arrays arranged in chiral configurations of prescribed handedness is highly attractive for the design of new functional materials; however, this remains a formidable challenge in nanotechnology. In this study, we demonstrated the controlled arrangements of gold (Au) NPs into helical structures templated by helical pores created in cross-linked block copolymer (BCP) films. d- and l-tartaric acid (TA) were used to direct the self-assembly of achiral poly(1,4-butadiene)-b-poly(ethylene oxide) BCPs into helical cylindrical morphologies with prescribed handedness, i.e., D or L. Helical pores were generated by BCP cross-linking followed by TA extraction. Helical Au NP arrays, subsequently arranged within the helical pores, exhibited the chiral optical response. The helical structures of NPs arrays and the resulting optical handedness were tunable simply by using either D- or L-porous templates. This simple strategy offers a straightforward pathway for the fabrication of chiral porous BCP films and helical NPs arrays with chiral optical properties. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
49. High Molecular Mobility and Viscoelasticity of Microphase-Separated Bottlebrush Diblock Copolymer Melts.
- Author
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Yavitt, Benjamin M., Yue Gai, Dong-Po Song, Winter, H. Henning, and Watkins, James J.
- Published
- 2017
- Full Text
- View/download PDF
50. [Hammerhead ribozyme against human telomerase catalytic subunit (hTERT) induced apoptosis of liver cancer cells]
- Author
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Dong-po, Song, Ju-sheng, Lin, Gui-lian, Fu, Xue-mei, Sun, Xin-juan, Kong, Pei-yuan, Li, and Xin, Ma
- Subjects
DNA-Binding Proteins ,Cell Line, Tumor ,Liver Neoplasms ,Mutation ,Humans ,Apoptosis ,RNA, Catalytic ,Transfection ,Telomerase - Abstract
To construct vector pEGFP-C1-hTERT-ribozyme (pGTRz-U6) and its mutant (pGTmRz-U6) against hTERT containing U6 promoter, then transfect them into human liver cancer cell line SMMC7721 to observe the action of the human telomerase catalytic subunit (hTERT) hammerhead ribozyme on proliferation and apoptosis of human liver cancer cell SMMC7721.Eukaryotic expressing vector pGTRz-U6 and mutant pGTmRz-U6 were constructed and transfected into SMMC7721 using Lipofectamine2000 Reagent, with pEGFP-C1 as the control group. After strict screening by G418, positive clones were cultured; the amount of expression of ribozyme and hTERT was detected by RT-PCR; cell proliferation by MTT; telomerase activity by TRAP and silver staining assay; cell apoptosis by FCM.We found that the two ribozymes were expressed persistently in SMMC7721; different expression levels (P0.01) of hTERT among SMMC7721-Rz, SMMC7721-mRz and SMMC7721-pEGFP-C1 was exhibited by the analysis of variance with SPSS software. The difference between SMMC7721-Rz and the others is significant in t-test (P0.01), while there was no difference between SMMC7721-mRz and SMMC7721-pEGFP-C1 (P0.05). With the advance of cell division, telomerase activities of the cells treated by SMMC7721-Rz and SMMC7721-mRz decreased gradually, and the percentage of apoptosis of the cells transfected with Rz and mRz increased gradually. The apoptosis percentage of 7PDS SMMC7721-Rz was 29.86%, while those of SMMC7721-mRz and SMMC7721-pEGFP-C1 were 9.87% and 3.36%, respectively.The apoptosis level of SMMC7721 induced by hTERT ribozyme increases as cells divide, and this ribozyme maybe a potential approach for liver cancer gene therapy.
- Published
- 2004
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