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2020 Volume 51 Issue 2
2020, 51(2):
Abstract:
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2020, 51(2): 125-135
doi: 10.11777/j.issn1000-3304.2019.19143
Abstract:
With the increasing demand for preventing and controlling of new/sudden diseases, major infectious diseases and malignant tumors, vaccines that based on traditional experience await updated. In terms of the unique physio-chemical advantages, polymeric micro/nano particles have become the research hotspots in the field of biomedical delivery. However, the rational integration of the micro/nano particles into vaccine delivery system is a huge challenge. On the basis of our research on the preparation and application of polymer micro/nano particles, an advanced strategy that co-assembles the particle “chassis” and subunit vaccines into one engineered vaccine is proposed. During the 20-year systematic study, new functions of polymeric particles are developed, and important mechanisms for the enhanced cellular/mucosal immunity are clarified. Apart from the chassis with conventional physiochemical property, other chassises with lysosomal escape merit, unique properties (deformability or mobility), or “Immunoticket” advantage have been exploited. The present paper not only summarizes our work but also involves international research progress, which sheds light upon the engineered vaccine chassises for their on-demand design concept, relative mechanism and development.
With the increasing demand for preventing and controlling of new/sudden diseases, major infectious diseases and malignant tumors, vaccines that based on traditional experience await updated. In terms of the unique physio-chemical advantages, polymeric micro/nano particles have become the research hotspots in the field of biomedical delivery. However, the rational integration of the micro/nano particles into vaccine delivery system is a huge challenge. On the basis of our research on the preparation and application of polymer micro/nano particles, an advanced strategy that co-assembles the particle “chassis” and subunit vaccines into one engineered vaccine is proposed. During the 20-year systematic study, new functions of polymeric particles are developed, and important mechanisms for the enhanced cellular/mucosal immunity are clarified. Apart from the chassis with conventional physiochemical property, other chassises with lysosomal escape merit, unique properties (deformability or mobility), or “Immunoticket” advantage have been exploited. The present paper not only summarizes our work but also involves international research progress, which sheds light upon the engineered vaccine chassises for their on-demand design concept, relative mechanism and development.
2020, 51(2): 136-147
doi: 10.11777/j.issn1000-3304.2019.19175
Abstract:
In recent decades, solid-state nuclear magnetic resonance (NMR) spectroscopy has been playing an important role in the characterization of polymer materials. To some degree, it has become one of the indispensable tools for studying the microstructures, segmental dynamics and inter-/intra-molecular interactions and elucidating the structure-functionality-property relationship of multiphase polymer materials, because the anisotropic spin interactions in the molecules can be selectively manipulated via various radiofrequency pulse sequence design. As a result, NMR can provide important information on a length scale from 0.1 nm to 100 nm and a time scale from 1 ns to 100 s. Herein, in this current review article, we will review some of our recently developed solid-state NMR approaches specifically for applications in polymers, including quantitative determination of compositional contents, characterization of crosslinking/entanglement density and inhomogeneity of the network, hydrogen bonding interactions between segments, and so on. A variety of typical examples, including self-healing supramolecular rubbers, thermal reversible polyurethanes, dual-cross-linked hydrogels, elastomers, etc., are given in detail, showing how various solid-state NMR approaches were implemented to quantitatively characterizing the structures, molecular interactions, and crosslinking network. Furthermore, due to the presence of heterogeneous dynamic in multiphase polymers, the applications of traditional solid-state NMR techniques are sustainably limited, and we also developed corresponding novel solid-state NMR approaches to overcome the limitations and enhance the spectral resolution and signal sensitivity.
In recent decades, solid-state nuclear magnetic resonance (NMR) spectroscopy has been playing an important role in the characterization of polymer materials. To some degree, it has become one of the indispensable tools for studying the microstructures, segmental dynamics and inter-/intra-molecular interactions and elucidating the structure-functionality-property relationship of multiphase polymer materials, because the anisotropic spin interactions in the molecules can be selectively manipulated via various radiofrequency pulse sequence design. As a result, NMR can provide important information on a length scale from 0.1 nm to 100 nm and a time scale from 1 ns to 100 s. Herein, in this current review article, we will review some of our recently developed solid-state NMR approaches specifically for applications in polymers, including quantitative determination of compositional contents, characterization of crosslinking/entanglement density and inhomogeneity of the network, hydrogen bonding interactions between segments, and so on. A variety of typical examples, including self-healing supramolecular rubbers, thermal reversible polyurethanes, dual-cross-linked hydrogels, elastomers, etc., are given in detail, showing how various solid-state NMR approaches were implemented to quantitatively characterizing the structures, molecular interactions, and crosslinking network. Furthermore, due to the presence of heterogeneous dynamic in multiphase polymers, the applications of traditional solid-state NMR techniques are sustainably limited, and we also developed corresponding novel solid-state NMR approaches to overcome the limitations and enhance the spectral resolution and signal sensitivity.
2020, 51(2): 148-157
doi: 10.11777/j.issn1000-3304.2019.19131
Abstract:
We designed and synthetized a new non fullerene acceptor with an A-D-A structure, named IDTO2HT-2F, based on indacenobis(dithieno[3,2-b:2′,3′-d]pyran) for organic solar cells. The dithieno[3,2-b:2′,3′-d]pyran will improve the electron-donating capability of the unit and lift the highest occupied molecular orbital (HOMO). Thus, the band gap decreases, making the maximum absorption peak red-shift. Theoretical calculation based on density functional theory (DFT) proved the feasibility of this molecular design. The molecule IDTO2HT-2F has a narrow bang gap of 1.30 eV with the solid absorption edge extended to 956 nm, which is complementary to that of the polymer PM6 film. The broad absorption of the active layer ensures the photovoltaic device to produce high photocurrent. With 0.5% DIO additive and thermal annealing at 120 °C for 10 min, the organic solar cell based on the acceptor IDTO2HT-2F and the polymer PM6 exhibits a power conversion efficiency (PCE) of 10.85% with a short circuit current density (Jsc) of 20.61 mA cm−2, an open-circuit voltage (Voc) of 0.86 V and a fill factor (FF) of 0.62. The results indicate that the strategy of introducing pyran into the molecular backbone is an effective way to tune the absorption and energy level of the molecules, which is also a promising method to design new non fullerene acceptors.
We designed and synthetized a new non fullerene acceptor with an A-D-A structure, named IDTO2HT-2F, based on indacenobis(dithieno[3,2-b:2′,3′-d]pyran) for organic solar cells. The dithieno[3,2-b:2′,3′-d]pyran will improve the electron-donating capability of the unit and lift the highest occupied molecular orbital (HOMO). Thus, the band gap decreases, making the maximum absorption peak red-shift. Theoretical calculation based on density functional theory (DFT) proved the feasibility of this molecular design. The molecule IDTO2HT-2F has a narrow bang gap of 1.30 eV with the solid absorption edge extended to 956 nm, which is complementary to that of the polymer PM6 film. The broad absorption of the active layer ensures the photovoltaic device to produce high photocurrent. With 0.5% DIO additive and thermal annealing at 120 °C for 10 min, the organic solar cell based on the acceptor IDTO2HT-2F and the polymer PM6 exhibits a power conversion efficiency (PCE) of 10.85% with a short circuit current density (Jsc) of 20.61 mA cm−2, an open-circuit voltage (Voc) of 0.86 V and a fill factor (FF) of 0.62. The results indicate that the strategy of introducing pyran into the molecular backbone is an effective way to tune the absorption and energy level of the molecules, which is also a promising method to design new non fullerene acceptors.
2020, 51(2): 158-165
doi: 10.11777/j.issn1000-3304.2019.19140
Abstract:
Intrinsic self-healing elastomers, which can automatically heal themselves after damage without the addition of other reagents, have recently attracted increasing attention. However, a trade-off commonly exists between high mechanical properties and high self-healing efficiency, which is always the bottle-neck in advancing these high performance self-healing elastomers. To solve this problem, a high performance and high self-healing efficiency elastomer was developed in this work based on hydrogen bonds and Diles-Alder (DA) crosslinks. Firstly, a monomer (HM) functionalized with amido bond and carbamic acid ester for the generation of hydrogen bonds was synthesized by N-butyl isocyanate and N-(2-hydroxyethyl)acrylamide. Next, one-pot free-radical copolymerization of HM, butyl acrylate (BA), and furfuryl methacrylate (FMA) was carried out to afford a linear copolymer, which was only cross-linked with hydrogen bonds. Finally, bismaleimide (BMI) was used to crosslink the linear copolymer through DA reaction. A double network self-healing elastomer with two kinds of crosslinks, i.e. hydrogen bonds and DA bonds, was thus prepared. The heating-up and cooling down FTIR spectroscopy was used to characterize the hydrogen bonds, while the existence of DA bonds was proved by FTIR, DSC, and DMA techniques. When an external force was applied, the hydrogen bonds broke firstly to dissipate energy, which helped to increase the toughness by about 6.2 times, the tensile strength by about 12.3 times, and Young’s modulus of the elastomer by about 26 times. Meanwhile, DA crosslinks endowed the elastomer with certain elasticity and the capability of fast shape recovery. Moreover, thanks to the reversible ability of hydrogen bonds and DA crosslinks, the elastomer exhibited a high self-healing efficiency up to 98%.
Intrinsic self-healing elastomers, which can automatically heal themselves after damage without the addition of other reagents, have recently attracted increasing attention. However, a trade-off commonly exists between high mechanical properties and high self-healing efficiency, which is always the bottle-neck in advancing these high performance self-healing elastomers. To solve this problem, a high performance and high self-healing efficiency elastomer was developed in this work based on hydrogen bonds and Diles-Alder (DA) crosslinks. Firstly, a monomer (HM) functionalized with amido bond and carbamic acid ester for the generation of hydrogen bonds was synthesized by N-butyl isocyanate and N-(2-hydroxyethyl)acrylamide. Next, one-pot free-radical copolymerization of HM, butyl acrylate (BA), and furfuryl methacrylate (FMA) was carried out to afford a linear copolymer, which was only cross-linked with hydrogen bonds. Finally, bismaleimide (BMI) was used to crosslink the linear copolymer through DA reaction. A double network self-healing elastomer with two kinds of crosslinks, i.e. hydrogen bonds and DA bonds, was thus prepared. The heating-up and cooling down FTIR spectroscopy was used to characterize the hydrogen bonds, while the existence of DA bonds was proved by FTIR, DSC, and DMA techniques. When an external force was applied, the hydrogen bonds broke firstly to dissipate energy, which helped to increase the toughness by about 6.2 times, the tensile strength by about 12.3 times, and Young’s modulus of the elastomer by about 26 times. Meanwhile, DA crosslinks endowed the elastomer with certain elasticity and the capability of fast shape recovery. Moreover, thanks to the reversible ability of hydrogen bonds and DA crosslinks, the elastomer exhibited a high self-healing efficiency up to 98%.
2020, 51(2): 166-173
doi: 10.11777/j.issn1000-3304.2019.19115
Abstract:
Heterophasic copolymerization of propylene based on MgCl2-supported Ziegler-Natta catalysts, that is, sequential propylene homopolymerization or copolymerization with minor amount of ethylene followed by ethylene/propylene random copolymerization for EPR, is a major polymerization technique in polypropylene industry, whose products, depending on their EPR contents, include high impact PP (hiPP, where EPR weight fraction is normally less than 40%) and thermophastic olefin elastomer (TPO, where EPR weight fraction is higher than 50 wt%). Compared to hiPP, the production of TPO is rather more challenging, for increased EPR contents makes it very difficult to prevent EPR from overflowing to the surfaces of the polymer particle, which will mess up with the particle morphology and lead to serious reactor fouling issues, affecting the production continuity. How to control the particle morphology at increased EPR contents with EPR being authentically contained inside without contaminating the surfaces has become a key scientific issue in further developing heterophasic copolymerization of propylene to TPO. This paper reports that the solution may lie in a simultaneous cross-linking of EPR using nonconjugated α,ω-diolefin during its polymerization. It is shown that simultaneous cross-linking can alter EPR’s viscoleastic properties to a great extent, exponentially increasing its low-shear viscosity and elasticity. As a result, EPR no longer poses as aggregated volatile droplets but rather large-size phase domains are formed by hot-compression; instead, it features dispersed particles discrete to each other. In turn, no overflowing of EPR occurs to the polymer particle surfaces. This research provides a solution for heterophasic copolymerization of propylene and polypropylene thermoplastic elastomer with high EPR content.
Heterophasic copolymerization of propylene based on MgCl2-supported Ziegler-Natta catalysts, that is, sequential propylene homopolymerization or copolymerization with minor amount of ethylene followed by ethylene/propylene random copolymerization for EPR, is a major polymerization technique in polypropylene industry, whose products, depending on their EPR contents, include high impact PP (hiPP, where EPR weight fraction is normally less than 40%) and thermophastic olefin elastomer (TPO, where EPR weight fraction is higher than 50 wt%). Compared to hiPP, the production of TPO is rather more challenging, for increased EPR contents makes it very difficult to prevent EPR from overflowing to the surfaces of the polymer particle, which will mess up with the particle morphology and lead to serious reactor fouling issues, affecting the production continuity. How to control the particle morphology at increased EPR contents with EPR being authentically contained inside without contaminating the surfaces has become a key scientific issue in further developing heterophasic copolymerization of propylene to TPO. This paper reports that the solution may lie in a simultaneous cross-linking of EPR using nonconjugated α,ω-diolefin during its polymerization. It is shown that simultaneous cross-linking can alter EPR’s viscoleastic properties to a great extent, exponentially increasing its low-shear viscosity and elasticity. As a result, EPR no longer poses as aggregated volatile droplets but rather large-size phase domains are formed by hot-compression; instead, it features dispersed particles discrete to each other. In turn, no overflowing of EPR occurs to the polymer particle surfaces. This research provides a solution for heterophasic copolymerization of propylene and polypropylene thermoplastic elastomer with high EPR content.
2020, 51(2): 174-182
doi: 10.11777/j.issn1000-3304.2019.19128
Abstract:
Vanadium catalysts always show outstanding catalytic properties towards ethylene (co)polymeriztaion, while the high-valent vanadium species would be deactivated because of the generation of inactive or less active low-valent species at elevated temperature and/or in prolonged time. As proved, introducing of bulky groups into the ligands is benefit to improving the catalytic properties of vanadium complexes. Herein, in order to well control the oxidation state of vanadium species, a series of tridentate β-ketoimine type vanadium(III) complexes bearing cyclic skeleton {[(R)X(C6H4)N＝CH(C6H5)C10H7O]VCl2(THF): 2a , R = CH3, X = S; 2b , R = CF3, X = S; 2c , R = Ph, X = S; 2d , R = tBu, X = S; 2e , R = Ph2, X = P; 2f , R = Ph, X = O}, were synthesized and characterized. Because of the constrained effects of the cyclic skeleton and the stabilizing effects of the bi-chelating ring, these synthesized catalysts showed high activities and improved stabilities in ethylene (co)polymerization. In the presences of Et2AlCl and ethyl trichloroacetate, catalysts 2a − 2f showed 8.16 − 19.9 kgpolymer/(mmolV·h), 7.68 − 26.9 kgpolymer/(mmolV·h) and 4.80 − 42.2 kgpolymer/(mmolV·h) of catalytic activities towards ethylene polymerization, ethylene/norbornene (NBE) copolymerization and ethylene/exo-1,4,4a,9,9a,10-hexahy-dro-9,10(1′,2′)-benzeno-1,4-methanoanthracene (HBM) copolymerization, respectively. All of the resultant polymers exhibited a unimodal distribution, indicating that these vanadium catalysts showed single-site catalytic behaviour, even at elevated temperatures (50 − 70 °C). Catalysts 2b , 2d , 2e and 2f showed “positive” comonomer effects in both ethylene/NBE copolymerization and ethylene/HBM copolymerization. Besides, 2a and 2c also exhibited “positive” comonomer effects in ethylene/HBM copolymerization. Cyclic olefin copolymers possessing high molecular weights (NBE: 43.1 − 66.4 kg/mol; HBM: 90.2 − 138 kg/mol) and high comonomer incorporations (NBE: 30.9 mol% − 42.1 mol%; HBM: 14.7 mol% − 25.0 mol%) were obtained facilely via direct copolymerization. The glass transition temperature is dominantly affected by the cyclic olefin incorporations and the steric hindrance of the cyclic olefin. Compared with the ethylene/NBE copolymers, the obtained ethylene/HBM copolymers showed much higher glass transition temperatures (NBE: 84 − 105 °C versus HBM: 173 − 188 °C).
Vanadium catalysts always show outstanding catalytic properties towards ethylene (co)polymeriztaion, while the high-valent vanadium species would be deactivated because of the generation of inactive or less active low-valent species at elevated temperature and/or in prolonged time. As proved, introducing of bulky groups into the ligands is benefit to improving the catalytic properties of vanadium complexes. Herein, in order to well control the oxidation state of vanadium species, a series of tridentate β-ketoimine type vanadium(III) complexes bearing cyclic skeleton {[(R)X(C6H4)N＝CH(C6H5)C10H7O]VCl2(THF): 2a , R = CH3, X = S; 2b , R = CF3, X = S; 2c , R = Ph, X = S; 2d , R = tBu, X = S; 2e , R = Ph2, X = P; 2f , R = Ph, X = O}, were synthesized and characterized. Because of the constrained effects of the cyclic skeleton and the stabilizing effects of the bi-chelating ring, these synthesized catalysts showed high activities and improved stabilities in ethylene (co)polymerization. In the presences of Et2AlCl and ethyl trichloroacetate, catalysts 2a − 2f showed 8.16 − 19.9 kgpolymer/(mmolV·h), 7.68 − 26.9 kgpolymer/(mmolV·h) and 4.80 − 42.2 kgpolymer/(mmolV·h) of catalytic activities towards ethylene polymerization, ethylene/norbornene (NBE) copolymerization and ethylene/exo-1,4,4a,9,9a,10-hexahy-dro-9,10(1′,2′)-benzeno-1,4-methanoanthracene (HBM) copolymerization, respectively. All of the resultant polymers exhibited a unimodal distribution, indicating that these vanadium catalysts showed single-site catalytic behaviour, even at elevated temperatures (50 − 70 °C). Catalysts 2b , 2d , 2e and 2f showed “positive” comonomer effects in both ethylene/NBE copolymerization and ethylene/HBM copolymerization. Besides, 2a and 2c also exhibited “positive” comonomer effects in ethylene/HBM copolymerization. Cyclic olefin copolymers possessing high molecular weights (NBE: 43.1 − 66.4 kg/mol; HBM: 90.2 − 138 kg/mol) and high comonomer incorporations (NBE: 30.9 mol% − 42.1 mol%; HBM: 14.7 mol% − 25.0 mol%) were obtained facilely via direct copolymerization. The glass transition temperature is dominantly affected by the cyclic olefin incorporations and the steric hindrance of the cyclic olefin. Compared with the ethylene/NBE copolymers, the obtained ethylene/HBM copolymers showed much higher glass transition temperatures (NBE: 84 − 105 °C versus HBM: 173 − 188 °C).
2020, 51(2): 183-190
doi: 10.11777/j.issn1000-3304.2019.19149
Abstract:
Gel polymer electrolytes (GPEs) for lithium ion batteries (LIBs) have attracted great attention due to their high ionic conductivity and safety, but it is still a great challenge to develop GPEs which can be used at high temperature in specific applications, such as oil drilling, mining, military and aerospace electronics. Cross-linking is one of the efficient methods for enhancing the thermal stabilities of GPEs. In this work, crosslinked gel polymer electrolytes (e-CGPEs) were made by electrospinning and Friedel-Crafts alkylation reaction. First of all, electrospun polymer membranes (e-PMs) were prepared by electrospinning technique with poly(vinylidene fluoride) (PVDF) as the matrix and polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-PEO-PS) triblock copolymer as the additive. Then the styrene units in e-PMs were crosslinked by Friedel-Crafts alkylation reaction to give electrospun crosslinked polymer membranes (e-CPMs). e-CPMs were activated by absorbing electrolytes to give crosslinked gel polymer electrolytes (e-CGPEs). The effects of PS-PEO-PS content (3%, 5%, 10%, 20%) on the properties of e-CPMs and e-CGPEs were also discussed. The results show that the content of PS-PEO-PS can affect the crystallinity, electrolyte uptake and crosslinked degree of e-CPMs, which may have influences on the ionic conductivity. Owing to the abundant crosslinked networks, high-temperature dimensional stabilities of e-CPMs are much better than that of electrospun PVDF membrane and commercial polypropylene (PP) membrane. All e-CPMs show almost no dimensional shrinkage at 160 °C, indicating that e-CPMs can be efficient precursors of GPEs used at high temperature. e-CGPEs have better electrochemical performances than the PVDF-based GPE (e-PVDF), due to their high porosity, electrolyte uptake and ionic conductivity. Among all the e-CGPEs, e-CGPE 5% with proper PS-PEO-PS content and crosslinked degree possesses the highest ionic conductivity of 6.52 mS/cm at room temperature. The half-cell assembled by e-CGPE 5% shows a discharge specific capacity of 83.5 mAh/g at 2 C. e-CGPEs also exhibit excellent cycle and rate performances. e-CGPE 5% has a capacity retention of 99.7% after 100 cycles at 0.1 C. All the results suggest that e-CGPEs have potential application value in high-efficiency lithium ion batteries which could be used at high temperature. And this work also provides a new path for the preparation of crosslinked gel polymer electrolytes with high efficiency and good performance.
Gel polymer electrolytes (GPEs) for lithium ion batteries (LIBs) have attracted great attention due to their high ionic conductivity and safety, but it is still a great challenge to develop GPEs which can be used at high temperature in specific applications, such as oil drilling, mining, military and aerospace electronics. Cross-linking is one of the efficient methods for enhancing the thermal stabilities of GPEs. In this work, crosslinked gel polymer electrolytes (e-CGPEs) were made by electrospinning and Friedel-Crafts alkylation reaction. First of all, electrospun polymer membranes (e-PMs) were prepared by electrospinning technique with poly(vinylidene fluoride) (PVDF) as the matrix and polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-PEO-PS) triblock copolymer as the additive. Then the styrene units in e-PMs were crosslinked by Friedel-Crafts alkylation reaction to give electrospun crosslinked polymer membranes (e-CPMs). e-CPMs were activated by absorbing electrolytes to give crosslinked gel polymer electrolytes (e-CGPEs). The effects of PS-PEO-PS content (3%, 5%, 10%, 20%) on the properties of e-CPMs and e-CGPEs were also discussed. The results show that the content of PS-PEO-PS can affect the crystallinity, electrolyte uptake and crosslinked degree of e-CPMs, which may have influences on the ionic conductivity. Owing to the abundant crosslinked networks, high-temperature dimensional stabilities of e-CPMs are much better than that of electrospun PVDF membrane and commercial polypropylene (PP) membrane. All e-CPMs show almost no dimensional shrinkage at 160 °C, indicating that e-CPMs can be efficient precursors of GPEs used at high temperature. e-CGPEs have better electrochemical performances than the PVDF-based GPE (e-PVDF), due to their high porosity, electrolyte uptake and ionic conductivity. Among all the e-CGPEs, e-CGPE 5% with proper PS-PEO-PS content and crosslinked degree possesses the highest ionic conductivity of 6.52 mS/cm at room temperature. The half-cell assembled by e-CGPE 5% shows a discharge specific capacity of 83.5 mAh/g at 2 C. e-CGPEs also exhibit excellent cycle and rate performances. e-CGPE 5% has a capacity retention of 99.7% after 100 cycles at 0.1 C. All the results suggest that e-CGPEs have potential application value in high-efficiency lithium ion batteries which could be used at high temperature. And this work also provides a new path for the preparation of crosslinked gel polymer electrolytes with high efficiency and good performance.
2020, 51(2): 191-197
doi: 10.11777/j.issn1000-3304.2019.19170
Abstract:
A polyacrylic acid two-dimensional photonic crystal hydrogel (PAA 2D-PCH) was prepared with acrylic acid as monomers, ethylene glycol dimethylacrylate as cross-linkers, 2,2-diethoxyacetophenone as initiators and polystyrene two-dimensional photonic crystal with bright diffraction under visible light illumination as a template, and its stimulating response properties to cationic surfactants were investigated. The results indicated that the PAA 2D-PCH had a sensitive response to cationic surfactants, while no response to anion, nonionic and zwitterionic surfactants. When the concentration of CPC, CPB and CTAB was increased from 0 to 4 × 10−3 mol/L, the diameter of Debye ring increased by 5.95, 5.50 and 4.95 cm, respectively, and the particle spacing decreased by 390, 364, and 341 nm, respectively. In the anionic surfactant, nonionic surfactant and zwitterionic surfactant solution, the diameter of Debye ring of the PAA 2D-PCH showed almost no change. The selective recognition of cationic surfactants by PAA 2D-PCH stemed from the electrostatic interaction between the negatively charged carboxylate ions and the cationic surfactants in the phosphate buffer solution of pH = 7.4, causing the PAA 2D-PCH shrunk, the particle spacing reduced, the diameter of the Debye ring increased, and the diffraction wavelength blue shifted. Study on the response behavior of PAA 2D-PCH to cationic surfactants by Debye ring method is easy to operate and has the characteristics of reusability and visualization, which is expected to be used for the determination of cationic surfactants in water.
A polyacrylic acid two-dimensional photonic crystal hydrogel (PAA 2D-PCH) was prepared with acrylic acid as monomers, ethylene glycol dimethylacrylate as cross-linkers, 2,2-diethoxyacetophenone as initiators and polystyrene two-dimensional photonic crystal with bright diffraction under visible light illumination as a template, and its stimulating response properties to cationic surfactants were investigated. The results indicated that the PAA 2D-PCH had a sensitive response to cationic surfactants, while no response to anion, nonionic and zwitterionic surfactants. When the concentration of CPC, CPB and CTAB was increased from 0 to 4 × 10−3 mol/L, the diameter of Debye ring increased by 5.95, 5.50 and 4.95 cm, respectively, and the particle spacing decreased by 390, 364, and 341 nm, respectively. In the anionic surfactant, nonionic surfactant and zwitterionic surfactant solution, the diameter of Debye ring of the PAA 2D-PCH showed almost no change. The selective recognition of cationic surfactants by PAA 2D-PCH stemed from the electrostatic interaction between the negatively charged carboxylate ions and the cationic surfactants in the phosphate buffer solution of pH = 7.4, causing the PAA 2D-PCH shrunk, the particle spacing reduced, the diameter of the Debye ring increased, and the diffraction wavelength blue shifted. Study on the response behavior of PAA 2D-PCH to cationic surfactants by Debye ring method is easy to operate and has the characteristics of reusability and visualization, which is expected to be used for the determination of cationic surfactants in water.
2020, 51(2): 198-204
doi: 10.11777/j.issn1000-3304.2019.19135
Abstract:
In the present work, based on the coordination capability of nitrile groups in nitrile rubber (NBR) with metal ions, a novel type of rubber material with sacrificial domains was designed. Specifically, copper sulfate (CuSO4) and vulcanization package were introduced into styrene-butadiene rubber (SBR)/NBR blend by mechanical mixing and hot pressing. As a result, SBR with sulfur crosslinkings are formed as continous phases while the NBR mainly crosslinked by Cu(II)-nitrile coordination bonds are acted as dispersed phases, which are used as deformable domains to reinforce SBR. With the increasing concentration of coordination bonds in dispersed phase, both strength and modulus of the rubber improve rapidly. When 20 wt% NBR was introduced, the strength and modulus of SBR are increased by 2.6-fold and 3.2-fold, respectively. The significant reinforcing effect of this system is attributed to the strong yet deformable domains. The strong domains have hydrodynamic effect, which greatly improve the moduli of the samples. On the other hand, upon external stress, the loading can be rapidly transferred from SBR matrix to the domains owning to strong interfacial interactions, forcing the domains to develop high-elastic deformation prior to the rupture of SBR chains and dissipate mechanical energy, thus significantly enhancing the toughness of the rubber. This forced high-elastic deformation in domains can be recoverd through relaxation at a high temperature to fully restore the mechanical properties. Overall, this work provides a new way for the reinforcement of non-polar rubber through the design of deformable domains.
In the present work, based on the coordination capability of nitrile groups in nitrile rubber (NBR) with metal ions, a novel type of rubber material with sacrificial domains was designed. Specifically, copper sulfate (CuSO4) and vulcanization package were introduced into styrene-butadiene rubber (SBR)/NBR blend by mechanical mixing and hot pressing. As a result, SBR with sulfur crosslinkings are formed as continous phases while the NBR mainly crosslinked by Cu(II)-nitrile coordination bonds are acted as dispersed phases, which are used as deformable domains to reinforce SBR. With the increasing concentration of coordination bonds in dispersed phase, both strength and modulus of the rubber improve rapidly. When 20 wt% NBR was introduced, the strength and modulus of SBR are increased by 2.6-fold and 3.2-fold, respectively. The significant reinforcing effect of this system is attributed to the strong yet deformable domains. The strong domains have hydrodynamic effect, which greatly improve the moduli of the samples. On the other hand, upon external stress, the loading can be rapidly transferred from SBR matrix to the domains owning to strong interfacial interactions, forcing the domains to develop high-elastic deformation prior to the rupture of SBR chains and dissipate mechanical energy, thus significantly enhancing the toughness of the rubber. This forced high-elastic deformation in domains can be recoverd through relaxation at a high temperature to fully restore the mechanical properties. Overall, this work provides a new way for the reinforcement of non-polar rubber through the design of deformable domains.
2020, 51(2): 205-213
doi: 10.11777/j.issn1000-3304.2019.19166
Abstract:
Sulfur, selenium-containing bonds, including disufide bond (SS), diselenide bond (SeSe), and selenide-sulfide bond (SeS), are an important type of light responsive dynamic covalent bonds. Among them, SS and SeS bonds can undergo exchange reaction with the irridiation of UV light, while SeSe bond only requires visible light due to its weaker bond energy. The purpose of this research is to use atomic force microscope-based single molecule force spectroscopy (AFM-SMFS) measurement to reveal the reasons behind the responsiveness and stability of S/Se related dynamic covalent bonds. In this study, quartz substrates modified by SS or SeSe bond were prepared via surface modification. Specifically, the quartz substrates were first washed with a mixture of sulfuric acid and hydrogen peroxide (volume ratio is 7:3), and then processed with oxygen plasma to obtain a hydrophilic surface. The surface then reacted with 3-aminopropyltriethoxysilane to form amino groups at the top, which further reacted with disulfide or diselenide containing diacid to afford SS or SeSe bond-modified substrates. The structures of the surfaces were comfirmed by water contact angle (WCA), atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry. Based on the light induced exchange reaction, wettabilities of the substrates were able to adjusted and were characterized by WCA and XPS. By exchanging with thiol or diselenide containing polymer, the polymer chain-attached substrates linked by a single bond of either SS, SeS, or SeSe could be obtained. The rupture forces of the three bonds were measured by SMFS. At a pulling speed of 200 nm/s, the rupture forces of SeSe, SeS and SS bonds were (1100 ± 300), (1320 ± 330), and (1450 ± 300) pN, respectively, indicating their strengths decreased as SS > SeS > SeSe. This result was consistent with the thermodynamic stability ranking of the three bonds. SMFS results illustrated that the strength of the dynamic covalent bond is between that of non-covalent interaction and that of robust covalent bond (e.g. C―C bond), which accounts for its balance of responsiveness and stability.
Sulfur, selenium-containing bonds, including disufide bond (SS), diselenide bond (SeSe), and selenide-sulfide bond (SeS), are an important type of light responsive dynamic covalent bonds. Among them, SS and SeS bonds can undergo exchange reaction with the irridiation of UV light, while SeSe bond only requires visible light due to its weaker bond energy. The purpose of this research is to use atomic force microscope-based single molecule force spectroscopy (AFM-SMFS) measurement to reveal the reasons behind the responsiveness and stability of S/Se related dynamic covalent bonds. In this study, quartz substrates modified by SS or SeSe bond were prepared via surface modification. Specifically, the quartz substrates were first washed with a mixture of sulfuric acid and hydrogen peroxide (volume ratio is 7:3), and then processed with oxygen plasma to obtain a hydrophilic surface. The surface then reacted with 3-aminopropyltriethoxysilane to form amino groups at the top, which further reacted with disulfide or diselenide containing diacid to afford SS or SeSe bond-modified substrates. The structures of the surfaces were comfirmed by water contact angle (WCA), atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry. Based on the light induced exchange reaction, wettabilities of the substrates were able to adjusted and were characterized by WCA and XPS. By exchanging with thiol or diselenide containing polymer, the polymer chain-attached substrates linked by a single bond of either SS, SeS, or SeSe could be obtained. The rupture forces of the three bonds were measured by SMFS. At a pulling speed of 200 nm/s, the rupture forces of SeSe, SeS and SS bonds were (1100 ± 300), (1320 ± 330), and (1450 ± 300) pN, respectively, indicating their strengths decreased as SS > SeS > SeSe. This result was consistent with the thermodynamic stability ranking of the three bonds. SMFS results illustrated that the strength of the dynamic covalent bond is between that of non-covalent interaction and that of robust covalent bond (e.g. C―C bond), which accounts for its balance of responsiveness and stability.
2020, 51(2): 214-220
doi: 10.11777/j.issn1000-3304.2019.19116
Abstract:
As one of the most powerful and popular chiral stationary phases (CSPs), phenylcarbamate derivatives of cellulose and amylose exhibit high chiral recognition ability and have realized efficent enantioseparation for almost 80% chiral compounds. To develop novel enantioseparation materials with high chiral recognition ability, it is of crucial importance to elucidate the chiral recognition mechanism for CSPs. Based on this, cellulose tris(phenylcarbamate) and amylose tris(phenylcarbamate) were synthesized by traditional esterification method in this study. The structures and degrees of substitution of the polysaccharide derivatives were characterized by 1H-NMR, implying that the obtained cellulose and amylose deivatives possessed regular higher order structures and almost complete substitution of phenylcarbamate pendants at three positions on the glucose units. The obtained polysaccharide derivatives were then coated on aminopropyl silica gel to prepare the chiral stationary phases (CSPs). The chiral recognition abilities of the derivatives were evaluated by the high performance liquid chromatography (HPLC) based on the separation of racemic 1-(9-anthryl)-2,2,2-trifluoroethanol (Rac-1). Then, based on the molecular mechanics and the molecular dynamics, molecular simulation of the higher order sturucture of polysaccharide derivatives were performed using Materials Studio software. The optimized conformation for the interaction between polysaccharide derivatives and enantiomers of Rac-1 was achieved by the molecular simulation according to the FTIR and XRD results. The molecular simulation results agreed well with the chiral recognition ability and elution order of enantiomers by HPLC. It indicated that the chiral recognition was significantly dependent on the synergistic interactions between polysaccharide derivatives and enantiomers of Rac-1 at the chiral grooves formed by the carbamate substituents and aromatic rings of the polysaccharide derivatives with different stabilities. This study may contribute to a better understanding for the chiral recognition mechanism of polymer-based CSPs.
As one of the most powerful and popular chiral stationary phases (CSPs), phenylcarbamate derivatives of cellulose and amylose exhibit high chiral recognition ability and have realized efficent enantioseparation for almost 80% chiral compounds. To develop novel enantioseparation materials with high chiral recognition ability, it is of crucial importance to elucidate the chiral recognition mechanism for CSPs. Based on this, cellulose tris(phenylcarbamate) and amylose tris(phenylcarbamate) were synthesized by traditional esterification method in this study. The structures and degrees of substitution of the polysaccharide derivatives were characterized by 1H-NMR, implying that the obtained cellulose and amylose deivatives possessed regular higher order structures and almost complete substitution of phenylcarbamate pendants at three positions on the glucose units. The obtained polysaccharide derivatives were then coated on aminopropyl silica gel to prepare the chiral stationary phases (CSPs). The chiral recognition abilities of the derivatives were evaluated by the high performance liquid chromatography (HPLC) based on the separation of racemic 1-(9-anthryl)-2,2,2-trifluoroethanol (Rac-1). Then, based on the molecular mechanics and the molecular dynamics, molecular simulation of the higher order sturucture of polysaccharide derivatives were performed using Materials Studio software. The optimized conformation for the interaction between polysaccharide derivatives and enantiomers of Rac-1 was achieved by the molecular simulation according to the FTIR and XRD results. The molecular simulation results agreed well with the chiral recognition ability and elution order of enantiomers by HPLC. It indicated that the chiral recognition was significantly dependent on the synergistic interactions between polysaccharide derivatives and enantiomers of Rac-1 at the chiral grooves formed by the carbamate substituents and aromatic rings of the polysaccharide derivatives with different stabilities. This study may contribute to a better understanding for the chiral recognition mechanism of polymer-based CSPs.
