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2019 Volume 50 Issue 9
2019, 50(9): 863-872
doi: 10.11777/j.issn1000-3304.2019.19085
Abstract:
Under healthy conditions, cells/tissues can function normally in their natural microenvironment due to the large amount of biomolecules herein. However, the normal cell/tissue microenvironment will be disrupted after certain pathological events due to the loss and damage associated with certain biological entities, and the disrupted microenvironment is usually accompanied by abnormal biological signals. Therefore, when designing biomaterials , one of the primary considerations is to restore the healthy cell/tissue microenvironment at the tissue-biomaterial interface and reconstruct the original biological structures in situ by mimicking human tissues, which is of critical importance to the total repair of the disease site. However, most of the existing biomaterials are biologically inert and lack interaction with the host. To improve the biocompatibility and biofunctionality of the substrate materials and to enhance their biomimeticity, the surface modification technology has gained increasing interest in recent decades. The rational modification of the tissue-biomaterial interface can improve beneficial interaction between the substrate material, while still preserving the physical properties of the material that are favorable for certain applications. Based on our previous study on cell/tissue biological and pathological environment, our group has carried out a lot research on the development of new biofunctional interfaces using polymer-based ligands or functional moieties, of which properties could be tailored according to the specific characteristics of particular microenvironment. The as-developed biomaterials could fulfill a variety of roles including osteogenic promotion, gene transfection, antibacterial and antitumor applications. It was also confirmed that these polymer-modified materials can autonomously interact with the biological tissues and execute the designed biological functions in a highly responsive manner. With the advances in synthesis chemistry and processing technology, new biomimetic materials with better fineness and structural precision will attract greater interest in related areas. In this paper, we will summarize the relevant research work in recent years and discuss those existing challenges.
Under healthy conditions, cells/tissues can function normally in their natural microenvironment due to the large amount of biomolecules herein. However, the normal cell/tissue microenvironment will be disrupted after certain pathological events due to the loss and damage associated with certain biological entities, and the disrupted microenvironment is usually accompanied by abnormal biological signals. Therefore, when designing biomaterials , one of the primary considerations is to restore the healthy cell/tissue microenvironment at the tissue-biomaterial interface and reconstruct the original biological structures in situ by mimicking human tissues, which is of critical importance to the total repair of the disease site. However, most of the existing biomaterials are biologically inert and lack interaction with the host. To improve the biocompatibility and biofunctionality of the substrate materials and to enhance their biomimeticity, the surface modification technology has gained increasing interest in recent decades. The rational modification of the tissue-biomaterial interface can improve beneficial interaction between the substrate material, while still preserving the physical properties of the material that are favorable for certain applications. Based on our previous study on cell/tissue biological and pathological environment, our group has carried out a lot research on the development of new biofunctional interfaces using polymer-based ligands or functional moieties, of which properties could be tailored according to the specific characteristics of particular microenvironment. The as-developed biomaterials could fulfill a variety of roles including osteogenic promotion, gene transfection, antibacterial and antitumor applications. It was also confirmed that these polymer-modified materials can autonomously interact with the biological tissues and execute the designed biological functions in a highly responsive manner. With the advances in synthesis chemistry and processing technology, new biomimetic materials with better fineness and structural precision will attract greater interest in related areas. In this paper, we will summarize the relevant research work in recent years and discuss those existing challenges.
2019, 50(9): 873-889
doi: 10.11777/j.issn1000-3304.2019.19100
Abstract:
Polymer semiconductors have attracted substantial interests in both academia and industry, recently, attributed to their distinctive advantages, including widely-tunable chemical structure and optoelectronic property, solution processability, and mechanical flexibility. In the last decade, a great deal of efforts have been dedicated to developing P-type (hole transporting) polymer semiconductors, however the development of N-type (electron transporting) polymer analogues lags far behind compared to their P-type counterparts due to the scarcity of highly electron-deficient building blocks, accompanied steric hindrance, and synthetic barriers. In fact, high-performance N-type polymer semiconductors are essential for organic complementary logic circuits and p-n junctions, hence it is imperative to develop high-performance N-type polymer semiconductors, which hinge on the design and synthesis of new electron deficient building blocks with compact geometry and good solubilizing capability. Among various electron deficient building blocks, imide-functionalized (hetero)arenes hold the most promising structural and electronic features for enabling N-type polymer semiconductors. This account summarizes the latest progress of N-type polymers, particularly the polymers based on imide-functionalized (hetero)arenes developed by our group. These new imide-functionalized (hetero)arenes include a series of ring-fused ladder-type heteroarenes up to 5 imide groups and 15 rings in a row, which offer a remarkable platform for developing N-type polymer semiconductors with widely tunable optoelectronic property and film morphology. In addition, a series of β-position functionalized or modified bithiophene imide derivatives are also devised and synthesized. The introduction of the most electronegative fluorine atom and the substitution of thiophene with more electron deficient thiazole yield further lower-lying LUMO energy levels, which promote N-type characteristics for the polymer semiconductors in devices. This account introduces the materials design principles for N-type polymer semiconductors and elaborate the synthetic routes to the new imides and the corresponding polymer semiconductors. In addition, the N-type device performance of the polymer semiconductors based on these imide-functionalized building blocks in organic field-effect transistors (OFETs) and polymer solar cells (PSCs) are commented, and the materials structure-property correlations are elaborated. Finally, our insights into future materials innovation of N-type polymer semiconductors by inventing new imide-functionalized building blocks are provided.
Polymer semiconductors have attracted substantial interests in both academia and industry, recently, attributed to their distinctive advantages, including widely-tunable chemical structure and optoelectronic property, solution processability, and mechanical flexibility. In the last decade, a great deal of efforts have been dedicated to developing P-type (hole transporting) polymer semiconductors, however the development of N-type (electron transporting) polymer analogues lags far behind compared to their P-type counterparts due to the scarcity of highly electron-deficient building blocks, accompanied steric hindrance, and synthetic barriers. In fact, high-performance N-type polymer semiconductors are essential for organic complementary logic circuits and p-n junctions, hence it is imperative to develop high-performance N-type polymer semiconductors, which hinge on the design and synthesis of new electron deficient building blocks with compact geometry and good solubilizing capability. Among various electron deficient building blocks, imide-functionalized (hetero)arenes hold the most promising structural and electronic features for enabling N-type polymer semiconductors. This account summarizes the latest progress of N-type polymers, particularly the polymers based on imide-functionalized (hetero)arenes developed by our group. These new imide-functionalized (hetero)arenes include a series of ring-fused ladder-type heteroarenes up to 5 imide groups and 15 rings in a row, which offer a remarkable platform for developing N-type polymer semiconductors with widely tunable optoelectronic property and film morphology. In addition, a series of β-position functionalized or modified bithiophene imide derivatives are also devised and synthesized. The introduction of the most electronegative fluorine atom and the substitution of thiophene with more electron deficient thiazole yield further lower-lying LUMO energy levels, which promote N-type characteristics for the polymer semiconductors in devices. This account introduces the materials design principles for N-type polymer semiconductors and elaborate the synthetic routes to the new imides and the corresponding polymer semiconductors. In addition, the N-type device performance of the polymer semiconductors based on these imide-functionalized building blocks in organic field-effect transistors (OFETs) and polymer solar cells (PSCs) are commented, and the materials structure-property correlations are elaborated. Finally, our insights into future materials innovation of N-type polymer semiconductors by inventing new imide-functionalized building blocks are provided.
2019, 50(9): 890-914
doi: 10.11777/j.issn1000-3304.2019.19097
Abstract:
Rechargeable batteries, which are among the most promising energy storage devices, have become a research hotspot related to energy-storage and energy-convert systems. While the rechargeable batteries based on liquid electrolytes commonly possess serious safety risks such as electrolyte leakage, volatilization, combustion, and explosion, polymer electrolytes display great potentials in ameliorating and addressing these problems. Conventional polymer electrolytes are generally prepared by the solution casting method, which is difficult to implement in actual production owing to its complicated operation and harsh conditions. In addition, the poor electrolyte/electrode interfacial contact in solid-state lithium batteries is also a common issue, mainly originating from the ex situ assembly technique of solid-state electrolyte. These drawbacks hinder their large-scale promotion and application. In this context have emerged the in situ generated polymer electrolytes, which aim at solving the above mentioned problems effectively. The general process of in situ preparation of the polymer electrolytes is as follows: a precursor solution consisting of monomers, lithium salts, and initiators is injected into the battery to fully wet the electrode channels and gaps, and the monomers are then polymerized in situ under certain external conditions to afford a gel/solid polymer rechargeable battery in one step. Compared to the traditional routes to polymer electrolytes, such in situ polymerization simplifies the preparation process, facilitates favorable solid electrolyte interface, and enables the electrode and electrolyte to form an integrated structure for better interfacial contact. These advantages are beneficial to an improved performance of rechargeable batteries and endow the technique with a promising application prospect. For more efficient development, it is an urgent task to review the existing process routes, reaction principles, types of polymer electrolytes, and the practical applications of in situ generated polymer electrolytes in rechargeable batteries (such as lithium, sodium, magnesium, etc.). Herein, we summarize the research progress of in situ polymerization in significantly stabilizing the electrode/electrolyte interface and inhibiting the diffusion of intermediates. Further, we discuss the challenges and development treads of in situ generated polymer electrolytes, including the prospects of quasi-solid polymer electrolytes. We believe this review paper will serve as a valuable reference and theoretical guidance for researchers engaged in polymer electrolytes.
Rechargeable batteries, which are among the most promising energy storage devices, have become a research hotspot related to energy-storage and energy-convert systems. While the rechargeable batteries based on liquid electrolytes commonly possess serious safety risks such as electrolyte leakage, volatilization, combustion, and explosion, polymer electrolytes display great potentials in ameliorating and addressing these problems. Conventional polymer electrolytes are generally prepared by the solution casting method, which is difficult to implement in actual production owing to its complicated operation and harsh conditions. In addition, the poor electrolyte/electrode interfacial contact in solid-state lithium batteries is also a common issue, mainly originating from the ex situ assembly technique of solid-state electrolyte. These drawbacks hinder their large-scale promotion and application. In this context have emerged the in situ generated polymer electrolytes, which aim at solving the above mentioned problems effectively. The general process of in situ preparation of the polymer electrolytes is as follows: a precursor solution consisting of monomers, lithium salts, and initiators is injected into the battery to fully wet the electrode channels and gaps, and the monomers are then polymerized in situ under certain external conditions to afford a gel/solid polymer rechargeable battery in one step. Compared to the traditional routes to polymer electrolytes, such in situ polymerization simplifies the preparation process, facilitates favorable solid electrolyte interface, and enables the electrode and electrolyte to form an integrated structure for better interfacial contact. These advantages are beneficial to an improved performance of rechargeable batteries and endow the technique with a promising application prospect. For more efficient development, it is an urgent task to review the existing process routes, reaction principles, types of polymer electrolytes, and the practical applications of in situ generated polymer electrolytes in rechargeable batteries (such as lithium, sodium, magnesium, etc.). Herein, we summarize the research progress of in situ polymerization in significantly stabilizing the electrode/electrolyte interface and inhibiting the diffusion of intermediates. Further, we discuss the challenges and development treads of in situ generated polymer electrolytes, including the prospects of quasi-solid polymer electrolytes. We believe this review paper will serve as a valuable reference and theoretical guidance for researchers engaged in polymer electrolytes.
2019, 50(9): 915-924
doi: 10.11777/j.issn1000-3304.2019.19051
Abstract:
The self-assembly of symmetric ABA tri-block copolymers inside an oil-in-water emulsion droplet upon solvent evaporation is investigated by Monte Carlo simulations, and the simulation results are compared with those in AB di-block copolymer systems. A morphological phase diagram is constructed in the two-dimensional space composed of surfactant concentration (φ) and the volume fraction of B segments (fB). Non-porosity particles, closed-porosity particles, open-porosity particles, capsules, and micelles are observed. The study shows that when fB ≤ 1/2, the increase of φ leads to a morphological evolution from non-porosity particle to closed-porosity particle and open-porosity particle, while for fB > 1/2, micelles are observed in a larger φ window. The fraction of bridge chains (vB) as a function of φ is always much lower than the corresponding bulk value. Moreover, the mean-square radius of gyration (<Rg2>) of the ABA tri-block copolymer chains is much smaller than that of the corresponding AB di-block copolymer chains with the same fB and φ values under the same condition. Due to the influence of chain conformation, no capsule appears in the ABA tri-block copolymer system when fB ≤ 1/2, which is different from the case of the corresponding AB di-block copolymer system. The specific surface area of particles with the same morphology falls into almost the same p regime, which indicates that the particle morphology largely determines its specific surface area. By calculating the formation energy of particles, it is confirmed that the surfactants in the system are the key to the formation of porous particles. All these are the same as what have been observed in AB di-block copolymer systems. In addition, the radial density distributions of water molecules in ABA tri-block system and the corresponding AB di-block system are not exactly the same, but the particle sizes are basically identical. The evolution processes including the typical non-porosity particles, closed-porosity particles, and open-porosity particles, as well as the bridging fraction during solvent evaporation are further discussed.
The self-assembly of symmetric ABA tri-block copolymers inside an oil-in-water emulsion droplet upon solvent evaporation is investigated by Monte Carlo simulations, and the simulation results are compared with those in AB di-block copolymer systems. A morphological phase diagram is constructed in the two-dimensional space composed of surfactant concentration (φ) and the volume fraction of B segments (fB). Non-porosity particles, closed-porosity particles, open-porosity particles, capsules, and micelles are observed. The study shows that when fB ≤ 1/2, the increase of φ leads to a morphological evolution from non-porosity particle to closed-porosity particle and open-porosity particle, while for fB > 1/2, micelles are observed in a larger φ window. The fraction of bridge chains (vB) as a function of φ is always much lower than the corresponding bulk value. Moreover, the mean-square radius of gyration (<Rg2>) of the ABA tri-block copolymer chains is much smaller than that of the corresponding AB di-block copolymer chains with the same fB and φ values under the same condition. Due to the influence of chain conformation, no capsule appears in the ABA tri-block copolymer system when fB ≤ 1/2, which is different from the case of the corresponding AB di-block copolymer system. The specific surface area of particles with the same morphology falls into almost the same p regime, which indicates that the particle morphology largely determines its specific surface area. By calculating the formation energy of particles, it is confirmed that the surfactants in the system are the key to the formation of porous particles. All these are the same as what have been observed in AB di-block copolymer systems. In addition, the radial density distributions of water molecules in ABA tri-block system and the corresponding AB di-block system are not exactly the same, but the particle sizes are basically identical. The evolution processes including the typical non-porosity particles, closed-porosity particles, and open-porosity particles, as well as the bridging fraction during solvent evaporation are further discussed.
2019, 50(9): 925-931
doi: 10.11777/j.issn1000-3304.2019.19052
Abstract:
Azobenzene (Azo) can absorb specific wavelength light that makes a change from trans-state to cis-state structure. Energy storage can be achieved by the difference in energy levels between the two isomers, so Azo is often used as energy storage materials. The conventional Azo photo-thermal storage materials have problems of relying on the utilization of ultraviolet light, requiring a high temperature stimulation, and a low-rate heat release. Herein, by utilizing diazonium salt method to introduce thiazole and methoxy groups into Azo to form a push-pull electronic structure, thiazole-heterocyclic Azo (t-Azo-h) achieves fast heat release. The photo-thermal storage composite (t-Azo-h/rGO) is obtained through grafting azo monomers onto the surface of reduced graphene oxide (rGO). Due to the close accumulation of Azo units on the surface of rGO, t-Azo-h/rGO of graphene-templated assembly increases the intermolecular interaction, resulting in an energy storage density of 89 Wh/kg, a half-life of 10 h, and a high power density of 890 W/kg at a heating rate of 5 °C/min. UV spectrum shows the maximum absorption intensity is at 435 nm, realizing absorption of the violet region because of molecular polarizability increased due to push-pull electronic properties. Red shift of spectral absorption broadens the use of sunlight. Owing to fast heat release, t-Azo-h/rGO reaches the temperature difference of 2.6 °C under 60 °C and 3.8 °C under 80 °C, respectively. By designing thermochromic pigment in combination with photo-thermal film, the decoloration occurs in two thermochromic pigments (red → colorless at 62 °C, blue → colorless at 82 °C) due to the heat release of photo-thermal material under heat stimulation. The t-Azo-h/rGO with fast heat release achieves the thermal visualization by optimizing stimulus. By designing push-pull electronic structure, a kind of photo-thermal material with fast thermal output is obtained and photo-thermal material with rapid heat release could finish a higher power density output at low temperature than that of slow heat release. At last, the thermal display with temperature response is realized by combining thermochromic pigments. Thermal display is expected to be applied in temperature supervisory and information encryption field.
Azobenzene (Azo) can absorb specific wavelength light that makes a change from trans-state to cis-state structure. Energy storage can be achieved by the difference in energy levels between the two isomers, so Azo is often used as energy storage materials. The conventional Azo photo-thermal storage materials have problems of relying on the utilization of ultraviolet light, requiring a high temperature stimulation, and a low-rate heat release. Herein, by utilizing diazonium salt method to introduce thiazole and methoxy groups into Azo to form a push-pull electronic structure, thiazole-heterocyclic Azo (t-Azo-h) achieves fast heat release. The photo-thermal storage composite (t-Azo-h/rGO) is obtained through grafting azo monomers onto the surface of reduced graphene oxide (rGO). Due to the close accumulation of Azo units on the surface of rGO, t-Azo-h/rGO of graphene-templated assembly increases the intermolecular interaction, resulting in an energy storage density of 89 Wh/kg, a half-life of 10 h, and a high power density of 890 W/kg at a heating rate of 5 °C/min. UV spectrum shows the maximum absorption intensity is at 435 nm, realizing absorption of the violet region because of molecular polarizability increased due to push-pull electronic properties. Red shift of spectral absorption broadens the use of sunlight. Owing to fast heat release, t-Azo-h/rGO reaches the temperature difference of 2.6 °C under 60 °C and 3.8 °C under 80 °C, respectively. By designing thermochromic pigment in combination with photo-thermal film, the decoloration occurs in two thermochromic pigments (red → colorless at 62 °C, blue → colorless at 82 °C) due to the heat release of photo-thermal material under heat stimulation. The t-Azo-h/rGO with fast heat release achieves the thermal visualization by optimizing stimulus. By designing push-pull electronic structure, a kind of photo-thermal material with fast thermal output is obtained and photo-thermal material with rapid heat release could finish a higher power density output at low temperature than that of slow heat release. At last, the thermal display with temperature response is realized by combining thermochromic pigments. Thermal display is expected to be applied in temperature supervisory and information encryption field.
2019, 50(9): 932-938
doi: 10.11777/j.issn1000-3304.2019.19047
Abstract:
The fabrication of conductive hydrogels with electric-induced self-healing capability exhibits great significance to the development of safe and long-life electronic devices, expanding their application in the field of flexible electronics. For this purpose, the conductive, self-healing nanocomposite hydrogel was fabricated via in situ free radical polymerization with modified Au nanoparticles (NPs) as crosslinkers, poly(o-phenylenediamine) (PoPD) nanobelts as conductive additives and N-isopropyl acrylamide as monomer in the presence of initiator and catalyst. Before the polymerization, N,N-bis(acryloyl)cystamine (BACA) with vinyl groups in the molecular structure was introduced on the surface of Au NPs through the interaction of thiolate-Au (RS-Au) bonding. The successful binding behavior between Au NPs and BACA was confirmed by the transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The PoPD nanobelts with a length of nearly 100 μm and a diameter of 200 nm were prepared by mixing HAuCl4 and oPD solution, and further stirring it at room temperature. The conductivity of PoPD nanobelts could be greatly improved through the strategy of chemical doping by introducing Fe3+ into the aqueous solution. For example, the conductivity can be obtained as high as 5.5 S/m when the concentration of Fe3+ employed was 1 mol/L. By combining the obtained hydrogel network with uniform and compact polymer network, the produced hydrogel showed excellent stretchability (larger than 2400%) and mechanical strength (larger than 1.2 MPa). Impressively, motivated by the thermal instability and Joule's first law, the damaged hydrogel exhibited rapid and highly efficient self-healing performance when the external power supply was available, because of the heating power generated by hydrogels at the cracks. For example, by the aid of power supply with the electric current of 0.05 A, the damaged hydrogel could be healed in 15 min with the optimal healing efficiency of nearly 90%. This prominent performance would contribute greatly to the exploration of flexible electric devices with excellent real-time self-heal ability under the working state from functional hydrogels.
The fabrication of conductive hydrogels with electric-induced self-healing capability exhibits great significance to the development of safe and long-life electronic devices, expanding their application in the field of flexible electronics. For this purpose, the conductive, self-healing nanocomposite hydrogel was fabricated via in situ free radical polymerization with modified Au nanoparticles (NPs) as crosslinkers, poly(o-phenylenediamine) (PoPD) nanobelts as conductive additives and N-isopropyl acrylamide as monomer in the presence of initiator and catalyst. Before the polymerization, N,N-bis(acryloyl)cystamine (BACA) with vinyl groups in the molecular structure was introduced on the surface of Au NPs through the interaction of thiolate-Au (RS-Au) bonding. The successful binding behavior between Au NPs and BACA was confirmed by the transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The PoPD nanobelts with a length of nearly 100 μm and a diameter of 200 nm were prepared by mixing HAuCl4 and oPD solution, and further stirring it at room temperature. The conductivity of PoPD nanobelts could be greatly improved through the strategy of chemical doping by introducing Fe3+ into the aqueous solution. For example, the conductivity can be obtained as high as 5.5 S/m when the concentration of Fe3+ employed was 1 mol/L. By combining the obtained hydrogel network with uniform and compact polymer network, the produced hydrogel showed excellent stretchability (larger than 2400%) and mechanical strength (larger than 1.2 MPa). Impressively, motivated by the thermal instability and Joule's first law, the damaged hydrogel exhibited rapid and highly efficient self-healing performance when the external power supply was available, because of the heating power generated by hydrogels at the cracks. For example, by the aid of power supply with the electric current of 0.05 A, the damaged hydrogel could be healed in 15 min with the optimal healing efficiency of nearly 90%. This prominent performance would contribute greatly to the exploration of flexible electric devices with excellent real-time self-heal ability under the working state from functional hydrogels.
2019, 50(9): 939-948
doi: 10.11777/j.issn1000-3304.2019.19048
Abstract:
Polyoxazolines have drawn much attention by researchers because of their hydrophilicity, good biocompatibility, non-toxicity. Chemical modification on polyoxazolines and their derivatives by grafting reaction with other synthetic polymer chains is one of the most important ways to improve the comprehensive properties of polyoxazoline materials. The novel amphiphilic polystyrene-g-poly(2-ethyl-2-oxazoline), PS-g-PEOX, graft copolymers were prepared through the combination of " grafting from” method and cationic ring-opening polymerization of 2-ethyl-2-oxazoline using the polystyrene bearing chloromethyl functional groups as the macroinitiator in the presence of activator, such as potassium iodide (KI), silver perchlorate (AgClO4) or silver trifluoromethanesulfonate (AgCF3SO3). The chemical structure and composition of PS-g-PEOX graft copolymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). The results show that the novel amphiphilic PS-g-PEOX graft copolymers with various PEOX grafting contents ranging from 8% to 97% could be synthesized by changing the feed ratios of monomer and activator. The silver nanoparticle (5 – 10 nm) content in a range from 0.1% to 3.5% was uniformly dispersed in the PS-g-PEOX graft copolymer matrix. The microphase separation of amphiphilic PS-g-PEOX graft copolymer/silver nanoparticle nanocomposite was observed and the microscopic morphology was related to PEOX contents. The hydrophilicity of the amphiphilic PS-g-PEOX graft copolymers and water contact angle (WCA) increased with PEOX content. And the WCA of PS-g-PEOX graft copolymer film with 97% PEOX content is 24°. What’s more, amphiphilic PS-g-PEOX graft copolymers can form stable and uniform micro/nano micelles in water. The stable oil/water suspension can be produced by adding a small amount of PS-g-PEOX graft copolymer into the incompatible water/toluene mixed system. The topological structure which formed by introducing PEOX onto PS backbones is beneficial to improve the thermal stability of PEOX. The good hydrophilicity of PEOX branches in PS-g-PEOX graft copolymer does a favor to the anti-adsorption properties against bovine serum albumin. The graft copolymer/silver nanoparticle composites behave a good antibacterial activity against E. coli, which increased with the content of nano silver.
Polyoxazolines have drawn much attention by researchers because of their hydrophilicity, good biocompatibility, non-toxicity. Chemical modification on polyoxazolines and their derivatives by grafting reaction with other synthetic polymer chains is one of the most important ways to improve the comprehensive properties of polyoxazoline materials. The novel amphiphilic polystyrene-g-poly(2-ethyl-2-oxazoline), PS-g-PEOX, graft copolymers were prepared through the combination of " grafting from” method and cationic ring-opening polymerization of 2-ethyl-2-oxazoline using the polystyrene bearing chloromethyl functional groups as the macroinitiator in the presence of activator, such as potassium iodide (KI), silver perchlorate (AgClO4) or silver trifluoromethanesulfonate (AgCF3SO3). The chemical structure and composition of PS-g-PEOX graft copolymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR). The results show that the novel amphiphilic PS-g-PEOX graft copolymers with various PEOX grafting contents ranging from 8% to 97% could be synthesized by changing the feed ratios of monomer and activator. The silver nanoparticle (5 – 10 nm) content in a range from 0.1% to 3.5% was uniformly dispersed in the PS-g-PEOX graft copolymer matrix. The microphase separation of amphiphilic PS-g-PEOX graft copolymer/silver nanoparticle nanocomposite was observed and the microscopic morphology was related to PEOX contents. The hydrophilicity of the amphiphilic PS-g-PEOX graft copolymers and water contact angle (WCA) increased with PEOX content. And the WCA of PS-g-PEOX graft copolymer film with 97% PEOX content is 24°. What’s more, amphiphilic PS-g-PEOX graft copolymers can form stable and uniform micro/nano micelles in water. The stable oil/water suspension can be produced by adding a small amount of PS-g-PEOX graft copolymer into the incompatible water/toluene mixed system. The topological structure which formed by introducing PEOX onto PS backbones is beneficial to improve the thermal stability of PEOX. The good hydrophilicity of PEOX branches in PS-g-PEOX graft copolymer does a favor to the anti-adsorption properties against bovine serum albumin. The graft copolymer/silver nanoparticle composites behave a good antibacterial activity against E. coli, which increased with the content of nano silver.
2019, 50(9): 949-956
doi: 10.11777/j.issn1000-3304.2019.19050
Abstract:
Compared to conventional shape memory polymers, the reversible plasticity shape memory polymers (RPSMPs) emphasize deformation and fixation at the same temperature below its transition temperature. Due to the advantages of low energy consumption and simple deformation, it has received much attention in the fields of military, aerospace and biomedicine. So it is important to understand its whole deformation process and key influencing factors. The glass transition temperature (Tg) of polynorbornene (PNB) is around room temperature, which is in favor of reversible deformation. Therefore, in this study, PNB materials with low oil filling were prepared by using PNB as the matrix and adding environmentally friendly aromatic oils with different contents. The effects of plasticizing oil content, deformation temperature and relaxation time on the reversible plasticity shape memory properties of PNB materials were studied by differential scanning calorimeter (DSC), universal electronic tensile testing machine and dynamic mechanical analysis (DMA). The results show that the plasticizing oil can continuously adjust the Tg of the PNB materials to keep it near room temperature, which is beneficial to the reversible plasticity deformation and excellent mechanical properties. When the deformation temperature is lower than the glass transition initiation temperature 2 °C, the energy consumption for material deformation is lower, and the molecular chain motion activation energy is higher, so the movement of chain segments is limited when the applied force is removed, thus, the fixation ratio is higher. The deformation temperature has little effect on the material recovery ratio. Because of the ultra-high molecular weight of PNB, when the triggering temperature is much higher than its transition temperature (Tg + 50 °C), the molecular chain entropy increases, resulting in a large entropy elastic recovery force, so the recovery ratios of all the deformed samples at different temperatures are higher than 95.0%. It is concluded that PNB has an excellent reversible plasticity shape memory performance when the deforming temperature is 2 °C lower that its onset of glass transition temperature. In addition, prolonging the relaxation time can also increase the shape fixed ratio, but the degree is limited.
Compared to conventional shape memory polymers, the reversible plasticity shape memory polymers (RPSMPs) emphasize deformation and fixation at the same temperature below its transition temperature. Due to the advantages of low energy consumption and simple deformation, it has received much attention in the fields of military, aerospace and biomedicine. So it is important to understand its whole deformation process and key influencing factors. The glass transition temperature (Tg) of polynorbornene (PNB) is around room temperature, which is in favor of reversible deformation. Therefore, in this study, PNB materials with low oil filling were prepared by using PNB as the matrix and adding environmentally friendly aromatic oils with different contents. The effects of plasticizing oil content, deformation temperature and relaxation time on the reversible plasticity shape memory properties of PNB materials were studied by differential scanning calorimeter (DSC), universal electronic tensile testing machine and dynamic mechanical analysis (DMA). The results show that the plasticizing oil can continuously adjust the Tg of the PNB materials to keep it near room temperature, which is beneficial to the reversible plasticity deformation and excellent mechanical properties. When the deformation temperature is lower than the glass transition initiation temperature 2 °C, the energy consumption for material deformation is lower, and the molecular chain motion activation energy is higher, so the movement of chain segments is limited when the applied force is removed, thus, the fixation ratio is higher. The deformation temperature has little effect on the material recovery ratio. Because of the ultra-high molecular weight of PNB, when the triggering temperature is much higher than its transition temperature (Tg + 50 °C), the molecular chain entropy increases, resulting in a large entropy elastic recovery force, so the recovery ratios of all the deformed samples at different temperatures are higher than 95.0%. It is concluded that PNB has an excellent reversible plasticity shape memory performance when the deforming temperature is 2 °C lower that its onset of glass transition temperature. In addition, prolonging the relaxation time can also increase the shape fixed ratio, but the degree is limited.
2019, 50(9): 957-963
doi: 10.11777/j.issn1000-3304.2019.19056
Abstract:
The copolymerization of myrcene with styrene by the half-sandwich scandium complexes (C5H5)Sc(CH2SiMe3)2(THF) ( 1 ) and (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) ( 2 ) was studied. The structures and thermal properties of the obtained copolymers were characterized by NMR, GPC and DSC. The copolymerization of myrcene with styrene at room temperature had been achieved and the copolymerization activity reached up to 104 g polymer molSc–1 h–1. The myrcene-styrene copolymers with controllable compositions (myrcene content = 22 mol% – 83 mol%), high molecular weight (Mn = 4.8 × 104 – 11.3 × 104) and narrow molecular weight distribution (Mw/Mn = 1.49 – 1.99) were conveniently obtained by changing the feed ratio of myrcene and styrene. Significant influence of catalyst structure on the stereoselectivity and comonomer distribution sequences in the resulting copolymers was observed. In the copolymerization of myrcene and styrene catalyzed by scandium complex 1 , styrene started to incorporate into chains after myrene was almost completely consumed, and diblock copolymers containing cis-1,4-polymyrcene (selectivity 95%) block and atactic polystyrene block were obtained. The obtained copolymers with different myrcene contents possessed two glass transition temperatures (Tg, – 63 and 96 °C), close to those of cis-1,4-polymyrcene and atactic polystyrene. In contrast, in the copolymerization of myrcene and styrene catalyzed by scandium complex 2 , myrene content showed a gradient decline accompanied by styrene content increasing gradually, producing gradient copolymers containing 3,4-polymyrcene (3,4-selectivity 75%, cis-1,4-selectivity 25%) and syndiotactic polystyrene. The obtained copolymers with different myrcene contents possessed a Tg at –35 °C and a melting temperature (Tm) at 254 °C, originating from polymyrcene block and syndiotactic polystyrene block, respectively. There is a great difference in the reactivity ratios between myrcene and styrene in the copolymerization catalyzed by scandium 1 (rMy >> rSt). However, the gap between the reactivity ratios of myrcene and styrene in the copolymerization catalyzed by scandium complex 2 was much smaller (rMy = 8.47, rSt = 0.76) and gradient copolymers were generated.
The copolymerization of myrcene with styrene by the half-sandwich scandium complexes (C5H5)Sc(CH2SiMe3)2(THF) ( 1 ) and (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) ( 2 ) was studied. The structures and thermal properties of the obtained copolymers were characterized by NMR, GPC and DSC. The copolymerization of myrcene with styrene at room temperature had been achieved and the copolymerization activity reached up to 104 g polymer molSc–1 h–1. The myrcene-styrene copolymers with controllable compositions (myrcene content = 22 mol% – 83 mol%), high molecular weight (Mn = 4.8 × 104 – 11.3 × 104) and narrow molecular weight distribution (Mw/Mn = 1.49 – 1.99) were conveniently obtained by changing the feed ratio of myrcene and styrene. Significant influence of catalyst structure on the stereoselectivity and comonomer distribution sequences in the resulting copolymers was observed. In the copolymerization of myrcene and styrene catalyzed by scandium complex 1 , styrene started to incorporate into chains after myrene was almost completely consumed, and diblock copolymers containing cis-1,4-polymyrcene (selectivity 95%) block and atactic polystyrene block were obtained. The obtained copolymers with different myrcene contents possessed two glass transition temperatures (Tg, – 63 and 96 °C), close to those of cis-1,4-polymyrcene and atactic polystyrene. In contrast, in the copolymerization of myrcene and styrene catalyzed by scandium complex 2 , myrene content showed a gradient decline accompanied by styrene content increasing gradually, producing gradient copolymers containing 3,4-polymyrcene (3,4-selectivity 75%, cis-1,4-selectivity 25%) and syndiotactic polystyrene. The obtained copolymers with different myrcene contents possessed a Tg at –35 °C and a melting temperature (Tm) at 254 °C, originating from polymyrcene block and syndiotactic polystyrene block, respectively. There is a great difference in the reactivity ratios between myrcene and styrene in the copolymerization catalyzed by scandium 1 (rMy >> rSt). However, the gap between the reactivity ratios of myrcene and styrene in the copolymerization catalyzed by scandium complex 2 was much smaller (rMy = 8.47, rSt = 0.76) and gradient copolymers were generated.
2019, 50(9): 964-972
doi: 10.11777/j.issn1000-3304.2019.19049
Abstract:
Combining the advantages of information encoding and function realization, DNA-conjugated nanomaterials have attracted great attention recently. As a typical anisotropic material, gold nano-triangle is of great value due to the sharp vertices. However, the yield of nano-triange is not high through current wet synthesis. In order to solve this problem, we propose a new strategy of shape selective separation of gold nano-triangles with the assist of thiol-DNA. The attachment of DNA to the surface of gold nanoparticles, on one hand, can stabilize the nanoparticles by shielding the direct contact between gold nanoparticles and solution environment. On the other hand, according to the particle shape, size and the surface charge density, gold nanoparticles have different mobilities in the electric field. As a result, gold nanoparticles can be separated by gel electrophoresis. The DNA-assist purification method gives a yield of above 80% of gold nano-triangles, which is also universal for the separation of nano-triangles with different sizes. More importantly, the surface-modified DNA can simultaneously separate and encode gold nano-triangles. By rational designing the DNA sequence, nano-triangles can be assembled on DNA origami and higher-order structures can be constructed.
Combining the advantages of information encoding and function realization, DNA-conjugated nanomaterials have attracted great attention recently. As a typical anisotropic material, gold nano-triangle is of great value due to the sharp vertices. However, the yield of nano-triange is not high through current wet synthesis. In order to solve this problem, we propose a new strategy of shape selective separation of gold nano-triangles with the assist of thiol-DNA. The attachment of DNA to the surface of gold nanoparticles, on one hand, can stabilize the nanoparticles by shielding the direct contact between gold nanoparticles and solution environment. On the other hand, according to the particle shape, size and the surface charge density, gold nanoparticles have different mobilities in the electric field. As a result, gold nanoparticles can be separated by gel electrophoresis. The DNA-assist purification method gives a yield of above 80% of gold nano-triangles, which is also universal for the separation of nano-triangles with different sizes. More importantly, the surface-modified DNA can simultaneously separate and encode gold nano-triangles. By rational designing the DNA sequence, nano-triangles can be assembled on DNA origami and higher-order structures can be constructed.
