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2019 Volume 50 Issue 1
2019, 50(1):
Abstract:
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2019, 50(1): 1-12
doi: 10.11777/j.issn1000-3304.2018.18223
Abstract:
Conjugated polymer materials have properties of light-weight, flexibility, good solution processability, performance tunability and low manufacturing cost. Therefore they hold great promise in various applications like light-emitting diodes, photovoltaics, field effect transistors and sensors. Due to the weak intermolecular interactions between conjugated polymers, subtle chemical structure modification and fabrication process alteration will cause variation of molecule assembly behaviours at a broad range of length scale and change of device performance. Thus, complex and diverse multi-level self-assembly structures of conjugated polymers can be formed. This provides rational molecular design and future industrial application with theoretical basis and applicable design strategies. This also sheds light on understanding the " structure-function relationships” of conjugated polymer materials. For the first time, based on systematic comparison of similarity between multi-level self-assembly behaviours of conjugated polymers and proteins, this review proposes that the assemblies used in optoelectronic devices usually have quaternary structures as in proteins: the primary structure is the one-dimensional polymer chain connected by covalent bonding; the secondary structure is multiple polymer chain aggregates forming through interchain interactions like lamellar packing, π-π stacking and chain entanglement; the tertiary structure is the phase behaviour as crystalline and amorphous region with domain size and grain boundary; the quaternary structure is the phase segregation in multi-component mixture through interaction between different component and phase interfacial properties. Multi-level self-assembly behaviours are in concert with each other to functionalize conjugated polymer materials by light, electric, magnet and heat performances. This review summarizes recent progresses on studies of conjugated polymer multi-level self-assembly process, which provides us with a new prospect of better observing, understanding and guiding the conjugated polymer multi-level self-assembly process. And thereby the substantial relationship between chemical structure, fabrication processing, assembly behaviour and macroscopic physical process is established, and the optoelectronic properties of polymer materials is furthermore optimized.
Conjugated polymer materials have properties of light-weight, flexibility, good solution processability, performance tunability and low manufacturing cost. Therefore they hold great promise in various applications like light-emitting diodes, photovoltaics, field effect transistors and sensors. Due to the weak intermolecular interactions between conjugated polymers, subtle chemical structure modification and fabrication process alteration will cause variation of molecule assembly behaviours at a broad range of length scale and change of device performance. Thus, complex and diverse multi-level self-assembly structures of conjugated polymers can be formed. This provides rational molecular design and future industrial application with theoretical basis and applicable design strategies. This also sheds light on understanding the " structure-function relationships” of conjugated polymer materials. For the first time, based on systematic comparison of similarity between multi-level self-assembly behaviours of conjugated polymers and proteins, this review proposes that the assemblies used in optoelectronic devices usually have quaternary structures as in proteins: the primary structure is the one-dimensional polymer chain connected by covalent bonding; the secondary structure is multiple polymer chain aggregates forming through interchain interactions like lamellar packing, π-π stacking and chain entanglement; the tertiary structure is the phase behaviour as crystalline and amorphous region with domain size and grain boundary; the quaternary structure is the phase segregation in multi-component mixture through interaction between different component and phase interfacial properties. Multi-level self-assembly behaviours are in concert with each other to functionalize conjugated polymer materials by light, electric, magnet and heat performances. This review summarizes recent progresses on studies of conjugated polymer multi-level self-assembly process, which provides us with a new prospect of better observing, understanding and guiding the conjugated polymer multi-level self-assembly process. And thereby the substantial relationship between chemical structure, fabrication processing, assembly behaviour and macroscopic physical process is established, and the optoelectronic properties of polymer materials is furthermore optimized.
2019, 50(1): 13-26
doi: 10.11777/j.issn1000-3304.2018.18193
Abstract:
Organic polymer solar cells which have achieved rapid development in recent years, therefore, attract wide attention around the world. At present, compared with fullerene polymer solar cells, the energy conversion efficiency (PCE) of non-fullerene polymer solar cells has already exceeded 14%. Organic photovoltaic (OPV) materials were widely studied including small-molecule/polymer donors and small-molecule/polymer acceptors. However, the studies on random conjugated polymer donors and acceptors are relatively rare. By introducing the third component into D-A conjugated polymer system to construct random conjugated polymer donor or acceptor, the absorption and the electron orbital energy levels could be well adjusted, and the open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) could be improved. Moreover, this strategy could also decrease the crystallinity of D-A polymer donor or acceptor availably, promoting the formation of better blend film morphology, appropriate phase separation size, and increase the electron or hole mobility. In order to adjust blend topography, the design and synthesis of molecular structures played an important role to improve the PCE of organic solar cells. Adding different ratios of electron-rich unit or electron-deficient unit to lower the strong crystallinity of polymers, which resulted in large phase separation, is not conducive to effective charge transport, thus reducing the efficiency of organic photovoltaics. Based on this situation, fullerene/non-fullerene polymer organic solar cells with p-type random conjugated polymer as electron donor and n-type ternary conjugated polymer as electron acceptor are summarized. At present, the total polymer photovoltaic efficiency based on the polymer donor (PBDB-T) and the random conjugated polymer acceptor (PNDI-2T-TR) reach up to 8.13%, which is one of the highest energy conversion efficiencies of polymer organic solar cells using the random copolymer as the electron acceptor so far, showing a good development prospect. Finally, the future development of the random conjugated polymer solar cells is summarized and prospected in this review.
Organic polymer solar cells which have achieved rapid development in recent years, therefore, attract wide attention around the world. At present, compared with fullerene polymer solar cells, the energy conversion efficiency (PCE) of non-fullerene polymer solar cells has already exceeded 14%. Organic photovoltaic (OPV) materials were widely studied including small-molecule/polymer donors and small-molecule/polymer acceptors. However, the studies on random conjugated polymer donors and acceptors are relatively rare. By introducing the third component into D-A conjugated polymer system to construct random conjugated polymer donor or acceptor, the absorption and the electron orbital energy levels could be well adjusted, and the open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) could be improved. Moreover, this strategy could also decrease the crystallinity of D-A polymer donor or acceptor availably, promoting the formation of better blend film morphology, appropriate phase separation size, and increase the electron or hole mobility. In order to adjust blend topography, the design and synthesis of molecular structures played an important role to improve the PCE of organic solar cells. Adding different ratios of electron-rich unit or electron-deficient unit to lower the strong crystallinity of polymers, which resulted in large phase separation, is not conducive to effective charge transport, thus reducing the efficiency of organic photovoltaics. Based on this situation, fullerene/non-fullerene polymer organic solar cells with p-type random conjugated polymer as electron donor and n-type ternary conjugated polymer as electron acceptor are summarized. At present, the total polymer photovoltaic efficiency based on the polymer donor (PBDB-T) and the random conjugated polymer acceptor (PNDI-2T-TR) reach up to 8.13%, which is one of the highest energy conversion efficiencies of polymer organic solar cells using the random copolymer as the electron acceptor so far, showing a good development prospect. Finally, the future development of the random conjugated polymer solar cells is summarized and prospected in this review.
2019, 50(1): 27-35
doi: 10.11777/j.issn1000-3304.2018.18160
Abstract:
A series of phosphorescent polymers with aggregation-induced emission (AIE) feature were synthesized by palladium-catalyzed Suzuki polycondensation of tetraphenylethene (TPE), iridium complex and 9,9-dioctylfluorene. All the obtained polymers are soluble in common organic solvents, such as chloroform, dichloromethane and tetrahydrofuran (THF), at room temperature, but insoluble in water. Their thermal and photophysical properties, as well as AIE performance of the resulting phosphorescent polymers are investigated with different feed ratios of iridium complex varing from 0.5% to 4%. These polymers display good thermal properties with a high thermal degradation temperature (> 300 °C) and glass transition temperature (≈ 100 °C). Polymer PFTPE displays the maximum photoluminescent (PL) emission at 440 nm. Relative to PFTPE, all the phosphorescent polymers prepared with iridium complex feed ratios in the range of 0.5% − 4% emit green light with an emission peak at about 505 nm. AIE performances of these phosphorescent polymers are examined by studying the PL emission behaviour of their diluted mixture in THF/water under different water fractions (fw). The aggregates are prepared by adding different fractions (fw = 0% to 90%) of ultra-pure water into THF solution. Both PL intensity and quantum yield (ФPL) of PFTPE-Fir0.5 and PFTPE-Fir1 exhibit an upward trend with the increasing fw from 0% to 80%. However, when fw further increases from 80% to 90%, PL intensity and ФPL show downward trend. The maximum values of ФPL are 37.3% for PFTPE-FIr0.5 and 38.6% for PFTPE-FIr1, respectively. Similarly, PL intensity and ФPL of PFTPE-FIr2 and PFTPE-FIr4 display the same behaviour as PFTPE-FIr0.5 and PFTPE-FIr1. And PFTPE-FIr2 and PFTPE-FIr4 reach the maximum ФPL value of 37.2% and 39.9%, respectively, at fw of 30%. This indicates that these phosphorescent polymers have AIE feature, suggesting that they are potential materials for fabrication of organic light-emitting diodes and fluorescent sensors.
A series of phosphorescent polymers with aggregation-induced emission (AIE) feature were synthesized by palladium-catalyzed Suzuki polycondensation of tetraphenylethene (TPE), iridium complex and 9,9-dioctylfluorene. All the obtained polymers are soluble in common organic solvents, such as chloroform, dichloromethane and tetrahydrofuran (THF), at room temperature, but insoluble in water. Their thermal and photophysical properties, as well as AIE performance of the resulting phosphorescent polymers are investigated with different feed ratios of iridium complex varing from 0.5% to 4%. These polymers display good thermal properties with a high thermal degradation temperature (> 300 °C) and glass transition temperature (≈ 100 °C). Polymer PFTPE displays the maximum photoluminescent (PL) emission at 440 nm. Relative to PFTPE, all the phosphorescent polymers prepared with iridium complex feed ratios in the range of 0.5% − 4% emit green light with an emission peak at about 505 nm. AIE performances of these phosphorescent polymers are examined by studying the PL emission behaviour of their diluted mixture in THF/water under different water fractions (fw). The aggregates are prepared by adding different fractions (fw = 0% to 90%) of ultra-pure water into THF solution. Both PL intensity and quantum yield (ФPL) of PFTPE-Fir0.5 and PFTPE-Fir1 exhibit an upward trend with the increasing fw from 0% to 80%. However, when fw further increases from 80% to 90%, PL intensity and ФPL show downward trend. The maximum values of ФPL are 37.3% for PFTPE-FIr0.5 and 38.6% for PFTPE-FIr1, respectively. Similarly, PL intensity and ФPL of PFTPE-FIr2 and PFTPE-FIr4 display the same behaviour as PFTPE-FIr0.5 and PFTPE-FIr1. And PFTPE-FIr2 and PFTPE-FIr4 reach the maximum ФPL value of 37.2% and 39.9%, respectively, at fw of 30%. This indicates that these phosphorescent polymers have AIE feature, suggesting that they are potential materials for fabrication of organic light-emitting diodes and fluorescent sensors.
2019, 50(1): 36-43
doi: 10.11777/j.issn1000-3304.2018.18169
Abstract:
Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films were coated on fluorine-doped tin oxide (FTO) conductive glass substrates via facile screen printing, followed by a modification. The modification was realized through post-treatment, i.e., immersing the as-printed films into a mixed solution consisting of diluted H2SO4 and methanol, and baking at 120 °C after 10 min of dipping. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the surface morphology and the thickness changes of the films before and after treating. Electrical conductivity of the pristine and that of the treated films were calculated and compared, using sheet resistance and thickness, and the result was discussed based on X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Finally, PEDOT:PSS films were used as counter electrodes of dye-sensitized solar cells (DSSCs). The catalytic activity of the PEDOT:PSS films toward I3– reduction reaction was characterized by electrochemical impedance spectroscopy (EIS), and the photovoltaic performance of DSSCs assembled by the films was evaluated under the irradiation of simulated AM 1.5G condition. The results demonstrate that, the amorphous PEDOT:PSS films are uniformly coated on FTO substrates after screen printing, and the surface morphology of PEDOT:PSS experiences significant change after the modification by post-treatment, with significantly decreased thickness and slightly increased roughness. The electrical conductivity has been enhanced to more than three times of that in the pristine film, due to the partial removal of PSS rather than the improvement of crystallinity. The catalytic activity toward I3– reduction reaction is greatly enhanced, and the photovoltaic performance of the DSSCs assembled is also obviously improved, with the photo conversion efficiency increases from 5.12% to 6.64%. The increased PEDOT/PSS mass ratio, electrical conductivity and roughness of the PEDOT:PSS films after post-treatment is believed to be responsible for the improvedment of the photovoltaic performance of the DSSCs.
Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films were coated on fluorine-doped tin oxide (FTO) conductive glass substrates via facile screen printing, followed by a modification. The modification was realized through post-treatment, i.e., immersing the as-printed films into a mixed solution consisting of diluted H2SO4 and methanol, and baking at 120 °C after 10 min of dipping. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to investigate the surface morphology and the thickness changes of the films before and after treating. Electrical conductivity of the pristine and that of the treated films were calculated and compared, using sheet resistance and thickness, and the result was discussed based on X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Finally, PEDOT:PSS films were used as counter electrodes of dye-sensitized solar cells (DSSCs). The catalytic activity of the PEDOT:PSS films toward I3– reduction reaction was characterized by electrochemical impedance spectroscopy (EIS), and the photovoltaic performance of DSSCs assembled by the films was evaluated under the irradiation of simulated AM 1.5G condition. The results demonstrate that, the amorphous PEDOT:PSS films are uniformly coated on FTO substrates after screen printing, and the surface morphology of PEDOT:PSS experiences significant change after the modification by post-treatment, with significantly decreased thickness and slightly increased roughness. The electrical conductivity has been enhanced to more than three times of that in the pristine film, due to the partial removal of PSS rather than the improvement of crystallinity. The catalytic activity toward I3– reduction reaction is greatly enhanced, and the photovoltaic performance of the DSSCs assembled is also obviously improved, with the photo conversion efficiency increases from 5.12% to 6.64%. The increased PEDOT/PSS mass ratio, electrical conductivity and roughness of the PEDOT:PSS films after post-treatment is believed to be responsible for the improvedment of the photovoltaic performance of the DSSCs.
2019, 50(1): 44-54
doi: 10.11777/j.issn1000-3304.2018.18167
Abstract:
A series of glycopolymers were prepared through combining ring-opening metathesis polymerization (ROMP) and CuAAC reaction. Firstly, a wide range of exo-7-oxanorbornene derivative glycomonomers without protecting groups were synthesized via a copper(I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) reaction, including α-D-mannose, β-D-glucose, and β-D-galactose. A series of well-defined glycopolymers were then obtained from various types and proportions of the above glycomonomers using ring-opening metathesis polymerization (ROMP) with the 3rd Grubbs catalyst in homogeneous organic solvent. Molecular weight and polydispersity index (PDI) of the glycopolymers were characterized by NMR spectroscopy and GPC, from which the well-controlled molecular weight (Mn = 1.3 × 104 − 2.7 × 10 4) in narrow distribution (PDI = 1.22 ~ 1.45) was confirmed. Turbidity measurement, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) were carried out to investigate the specific recognition of glycopolymers with concanavalin A (Con A). Turbidimetric study suggested a stronger binding ability of glycopolymers with Con A at higher ratio of α-D-mannose in glycopolymers. In comparison, those composed solely of β-D-galactose (P9) or β-D-glucose (P5) could not bind to Con A. Dynamic light scattering experiments demonstrated that the particle sizes of glycopolymers containing α-D-mannose approached 1000 nm with the addition of Con A (originally 100 nm), while the glycopolymers without α-D-mannose showed little size variation. Binding constants (Ka) of the three glycopolymers P3 (50 mol% α-D-mannose, 50 mol% β-D-glucose), P7 (50 mol% α-D-mannose, 50 mol% β-D-galactose), and P11 (50 mol% α-D-mannose, 50 mol% non-sugar motif) with Con A were 1.58 × 106, 2.23 × 106, and 2.05 × 105 L/mol, respectively, as measured by isothermal titration calorimetry. P11 exhibited much weaker ability to bind with Con A than P3 andP7 did, which implied a synergistic effect of β-D-glucose and β-D-galactose on the recognition of α-D-mannose with Con A.
A series of glycopolymers were prepared through combining ring-opening metathesis polymerization (ROMP) and CuAAC reaction. Firstly, a wide range of exo-7-oxanorbornene derivative glycomonomers without protecting groups were synthesized via a copper(I)-catalyzed azide-alkyne Huisgen cycloaddition (CuAAC) reaction, including α-D-mannose, β-D-glucose, and β-D-galactose. A series of well-defined glycopolymers were then obtained from various types and proportions of the above glycomonomers using ring-opening metathesis polymerization (ROMP) with the 3rd Grubbs catalyst in homogeneous organic solvent. Molecular weight and polydispersity index (PDI) of the glycopolymers were characterized by NMR spectroscopy and GPC, from which the well-controlled molecular weight (Mn = 1.3 × 104 − 2.7 × 10 4) in narrow distribution (PDI = 1.22 ~ 1.45) was confirmed. Turbidity measurement, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) were carried out to investigate the specific recognition of glycopolymers with concanavalin A (Con A). Turbidimetric study suggested a stronger binding ability of glycopolymers with Con A at higher ratio of α-D-mannose in glycopolymers. In comparison, those composed solely of β-D-galactose (P9) or β-D-glucose (P5) could not bind to Con A. Dynamic light scattering experiments demonstrated that the particle sizes of glycopolymers containing α-D-mannose approached 1000 nm with the addition of Con A (originally 100 nm), while the glycopolymers without α-D-mannose showed little size variation. Binding constants (Ka) of the three glycopolymers P3 (50 mol% α-D-mannose, 50 mol% β-D-glucose), P7 (50 mol% α-D-mannose, 50 mol% β-D-galactose), and P11 (50 mol% α-D-mannose, 50 mol% non-sugar motif) with Con A were 1.58 × 106, 2.23 × 106, and 2.05 × 105 L/mol, respectively, as measured by isothermal titration calorimetry. P11 exhibited much weaker ability to bind with Con A than P3 andP7 did, which implied a synergistic effect of β-D-glucose and β-D-galactose on the recognition of α-D-mannose with Con A.
2019, 50(1): 55-61
doi: 10.11777/j.issn1000-3304.2018.18166
Abstract:
Polybenzoxazines (PBz) is a new type of phenolic-like resins, which have excellent properties such as good mechanical and thermal properties, no volatile release upon cure, and molecular designing flexiblility. However, their major drawbacks are the high curing temperature and similar brittleness as phenolic resins. In this study, organotin silsesquioxanes (DOSn-Bu) are synthesized via capping reaction based on disilanol-POSS and Bu2SnCl2. Due to the cage-type hybrid structure, the metal-based oligomeric silsesquioxane (POMSS) possesses good thermal stability and mechanical properties. The mental centers are Lewis acid that catalyze ring-opening polymerization of benzoxazine monomers. The structure of DOSn-Bu was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR) and X-ray single crystal diffraction. A series of benzoxazine/DOSn-Bu hybrid resins were prepared by ultrasonic blending. FTIR results showed that the benzoxazine began to ring-open at 160 – 180 °C. The results of DSC showed that the initial curing temperature decreased by almost 50 °C and the peak curing temperature decreased by approximately 30 °C with the addition of DOSn-Bu. The thermal and mechanical properties of the hybrid material with different DOSn-Bu incorporation were measured by dynamic mechanical thermal analysis (DMTA) and thermal gravimetric analysis (TGA). DMTA result showed that the storage modulus ( E′) and glass transition temperature of the hybrid materials were improved. When 2 wt% of DOSn-Bu was added, the resins retained high storage modulus (E′ = 2.1 GPa at 50 °C) and high glass transtion temperature (Tg = 228 °C). TGA study showed that the hybrid materials possessed good thermal stability. From the scanning electron microscopy (SEM) mapping, it was found that the Si and Sn elements were greatly distributed in the system, thereby indicating that the catalysts were uniformly dispersed in the system with good compatibility with the resin matrix. The fracture surface morphologies of the cured resin were investigated by SEM. The roughness of the fracture surface of the hybrid material was increased compared with that of the pure benzoxazine resin and its texture became more complicated.
Polybenzoxazines (PBz) is a new type of phenolic-like resins, which have excellent properties such as good mechanical and thermal properties, no volatile release upon cure, and molecular designing flexiblility. However, their major drawbacks are the high curing temperature and similar brittleness as phenolic resins. In this study, organotin silsesquioxanes (DOSn-Bu) are synthesized via capping reaction based on disilanol-POSS and Bu2SnCl2. Due to the cage-type hybrid structure, the metal-based oligomeric silsesquioxane (POMSS) possesses good thermal stability and mechanical properties. The mental centers are Lewis acid that catalyze ring-opening polymerization of benzoxazine monomers. The structure of DOSn-Bu was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR) and X-ray single crystal diffraction. A series of benzoxazine/DOSn-Bu hybrid resins were prepared by ultrasonic blending. FTIR results showed that the benzoxazine began to ring-open at 160 – 180 °C. The results of DSC showed that the initial curing temperature decreased by almost 50 °C and the peak curing temperature decreased by approximately 30 °C with the addition of DOSn-Bu. The thermal and mechanical properties of the hybrid material with different DOSn-Bu incorporation were measured by dynamic mechanical thermal analysis (DMTA) and thermal gravimetric analysis (TGA). DMTA result showed that the storage modulus ( E′) and glass transition temperature of the hybrid materials were improved. When 2 wt% of DOSn-Bu was added, the resins retained high storage modulus (E′ = 2.1 GPa at 50 °C) and high glass transtion temperature (Tg = 228 °C). TGA study showed that the hybrid materials possessed good thermal stability. From the scanning electron microscopy (SEM) mapping, it was found that the Si and Sn elements were greatly distributed in the system, thereby indicating that the catalysts were uniformly dispersed in the system with good compatibility with the resin matrix. The fracture surface morphologies of the cured resin were investigated by SEM. The roughness of the fracture surface of the hybrid material was increased compared with that of the pure benzoxazine resin and its texture became more complicated.
2019, 50(1): 62-70
doi: 10.11777/j.issn1000-3304.2018.18168
Abstract:
Cellulose has attracted considerable attention due to its unique advantages such as abundant availability, renewability, non-pollution, and biocompatibility. However, β-glucose units in cellulose backbone are vulnerable to erosion and degradation by aquatic microorganisms. The antibacterial modification of cellulose was proposed by covalently introducing sorbic acid through esterification process. Antibacterial cellulose sorbate films were prepared by one-step in situ reaction and immersion precipitation phase inversion process with wood-pulp cellulose as raw material, sorbic acid as antibacterial agent, and N,N'-dicyclohexylcarbodiimide (DCC) as dehydrating agent to improve its antibacterial performance. Among them, the molar ratio of hydroxyl in cellulose to sorbic acid was 1:2, the reaction temperature was 80 °C and the reaction time was 4, 6, 8, 10 and 12 h, respectively. The casting solutions were casted with casting knife of 250 μm thickness. And then antibacterial cellulose sorbate films were obtained after solvents evaporation and immersion precipitation process. The structure and performances of the obtained cellulose sorbate films were characterized by various methods such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG) and differential scanning calorimetry analysis (DSC). The new characteristic peak of ester group (1715 cm−1) in FTIR spectra indicated that cellulose sorbate films were successfully prepared by esterification reaction. XPS and 13C-NMR analysis results also showed the synthesis of cellulose sorbate. However, the crystal type and structure of cellulose had changed during esterification process. The results of TG and DSC showed that the effect of intra- and inter-molecular hydrogen bonds in cellulose were reduced or destroyed by the introduction of sorbic-acyl, leading to slightly lower thermal stability of the cellulose sorbate films. The dynamic contact antibacterial test results indicated that cellulose sorbate films had inhibitory effect on E. coli and S. aureus and possessed higher inhibition rate against S. aureus (99.2% − 100%) than that of E. coli (90.4% − 100%) due to different cell wall structures of E. coli and S. aureus. Therefore, the synthesized cellulose sorbate may have some potential applications in packing, environmental coatings, as well as some functional materials.
Cellulose has attracted considerable attention due to its unique advantages such as abundant availability, renewability, non-pollution, and biocompatibility. However, β-glucose units in cellulose backbone are vulnerable to erosion and degradation by aquatic microorganisms. The antibacterial modification of cellulose was proposed by covalently introducing sorbic acid through esterification process. Antibacterial cellulose sorbate films were prepared by one-step in situ reaction and immersion precipitation phase inversion process with wood-pulp cellulose as raw material, sorbic acid as antibacterial agent, and N,N'-dicyclohexylcarbodiimide (DCC) as dehydrating agent to improve its antibacterial performance. Among them, the molar ratio of hydroxyl in cellulose to sorbic acid was 1:2, the reaction temperature was 80 °C and the reaction time was 4, 6, 8, 10 and 12 h, respectively. The casting solutions were casted with casting knife of 250 μm thickness. And then antibacterial cellulose sorbate films were obtained after solvents evaporation and immersion precipitation process. The structure and performances of the obtained cellulose sorbate films were characterized by various methods such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG) and differential scanning calorimetry analysis (DSC). The new characteristic peak of ester group (1715 cm−1) in FTIR spectra indicated that cellulose sorbate films were successfully prepared by esterification reaction. XPS and 13C-NMR analysis results also showed the synthesis of cellulose sorbate. However, the crystal type and structure of cellulose had changed during esterification process. The results of TG and DSC showed that the effect of intra- and inter-molecular hydrogen bonds in cellulose were reduced or destroyed by the introduction of sorbic-acyl, leading to slightly lower thermal stability of the cellulose sorbate films. The dynamic contact antibacterial test results indicated that cellulose sorbate films had inhibitory effect on E. coli and S. aureus and possessed higher inhibition rate against S. aureus (99.2% − 100%) than that of E. coli (90.4% − 100%) due to different cell wall structures of E. coli and S. aureus. Therefore, the synthesized cellulose sorbate may have some potential applications in packing, environmental coatings, as well as some functional materials.
2019, 50(1): 71-81
doi: 10.11777/j.issn1000-3304.2018.18148
Abstract:
2-(6-Oxido-6H-dibenz<1 2="">oxaphosphorin-6-yl)-methanol (ODOPM) was synthesized by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) with methanal, and its structure was characterized by FTIR,1H-NMR, 31P-NMR and MS. The flame-retardant performance of ODOPM in poly(lactic acid) (PLA) was explored and compared with those of 2-(6-oxido-6H-dibenz<1 2="">oxaphosphorin-6-yl)-1,4-benzenediol (DOPO-HQ). The flame-retardant properties of PLA-based ODOPM and DOPO-HQ were further investigated by determining the limiting oxygen index (LOI) as well as conducting vertical burning (UL-94) and cone calorimeter tests; their thermal-degradation behavior was studied by thermogravimetric analysis (TG) measurements. The results indicated that both flame retardants could decrease the peak heat release rate (PHRR), improve LOI, and promote the thermal stability and char formation. At flame-retardant content of 15 wt%, PHRR was decreased from 571 kW/m2 of the neat PLA to ~ 430 kW/m2 for both PLA/ODOPM and PLA/DOPO-HQ composites, while the former showed a high LOI of 34.4%, 72% increase compared with neat PLA (LOI of 20%). Moreover, V-0 rating in UL-94 test was achieved by PLA/ODOPM composite with filler concentration at 5 wt%, but PLA/DOPO-HQ required 15 wt% filler to reach the same rating with only 28.8% for LOI. In addition, all the flame retardant PLA systems decomposed earlier than neat PLA under N2 condition, but the incorporation of ODOPM could increase the maximum degradation temperaeture (Tmax). Especially, Tmax of PLA containing 5 wt% ODOPM was 18 °C higher than that of neat PLA. However, PLA/ODOPM had generally lower Tmax than neat PLA did unless the fill concentration reached 15 wt%. Characterization of char morphology by Raman spectroscopy and scanning electron microscopy (SEM) showed that incorporation of DOPO-HQ was conducive to the formation of a compact cross-linked char layer. TG-FTIR results suggested that both two flame retardants exerted a gas-phase-flame inhibition effect. Energy-dispersive spectroscopy (EDS) demonstrated an increased P content in the carbon layer along with the increasing flame-retardant content, possibly attributed to polyphosphate formation. Rheological analysis indicated that PLA/ODOPM possessed weaker viscoelasticity compared with PLA/DOPO-HQ. Finally, the mechanical measurements on neat PLA and PLA composites, including tensile strength, flexural strength, and notch impact strength, showed that PLA/DOPO-HQ possessed better mechanical properties than PLA/ODOPM did.
2-(6-Oxido-6H-dibenz
2019, 50(1): 82-90
doi: 10.11777/j.issn1000-3304.2018.18137
Abstract:
In this work, we have studied the crystallization orientation behavior of poly(ɛ-caprolactone)-b-poly(l-lactide) (PCL-b-PLLA) under physically confined environment provided via a soft nanoimprinting lithography (NIL) process. The confined thin films were annealed and crystallized following two different routes, and the resulting morphology and crystal orientation were systematically investigated by atomic force microscopy (AFM) and grazing-incidence X-ray diffraction (GIXRD). Based on the large difference of the crystallization temperatures of PCL and PLLA, both one-step (T − Tc,PCL) and two-step crystallization (T − Tc,PLLA − Tc,PCL) processes were used. It was found that PCL crystals were successfully confined in the micromolded domains after one-step crystallization. Interestingly, the fast growth direction of PCL crystals (b-axis) was either along the normal or the parallel direction of the trench, depending on the flow mechanisms during the nanoimprinting process. In the melt nanoimprinting process, polymer melt was squeezed into the trench and forced into the normal direction by the shearing effect and the expanding of the soft mold. By contrast, in room temperature (RT) imprinting process, upon annealing, polymer melt went into the trench by the capillary force and the flow direction of polymer melt was inclined to along the trench. For two-step crystallization process, both PLLA and PCL crystal were confined in the trench. However, due to the high crystallization temperature of PLLA, in the first step of PLLA crystallization, no preferential growth orientation was observed. These results indicated that, without imprinting induced shear flow (which relaxed quickly at PLLA crystallization temperature), the physical confinement of the soft mold was not strong enough to guide the crystal growth direction. Subsequent second step of PCL crystallization was enhanced by the existing PLLA crystal, resulting randomly distributed crystal orientation.
In this work, we have studied the crystallization orientation behavior of poly(ɛ-caprolactone)-b-poly(l-lactide) (PCL-b-PLLA) under physically confined environment provided via a soft nanoimprinting lithography (NIL) process. The confined thin films were annealed and crystallized following two different routes, and the resulting morphology and crystal orientation were systematically investigated by atomic force microscopy (AFM) and grazing-incidence X-ray diffraction (GIXRD). Based on the large difference of the crystallization temperatures of PCL and PLLA, both one-step (T − Tc,PCL) and two-step crystallization (T − Tc,PLLA − Tc,PCL) processes were used. It was found that PCL crystals were successfully confined in the micromolded domains after one-step crystallization. Interestingly, the fast growth direction of PCL crystals (b-axis) was either along the normal or the parallel direction of the trench, depending on the flow mechanisms during the nanoimprinting process. In the melt nanoimprinting process, polymer melt was squeezed into the trench and forced into the normal direction by the shearing effect and the expanding of the soft mold. By contrast, in room temperature (RT) imprinting process, upon annealing, polymer melt went into the trench by the capillary force and the flow direction of polymer melt was inclined to along the trench. For two-step crystallization process, both PLLA and PCL crystal were confined in the trench. However, due to the high crystallization temperature of PLLA, in the first step of PLLA crystallization, no preferential growth orientation was observed. These results indicated that, without imprinting induced shear flow (which relaxed quickly at PLLA crystallization temperature), the physical confinement of the soft mold was not strong enough to guide the crystal growth direction. Subsequent second step of PCL crystallization was enhanced by the existing PLLA crystal, resulting randomly distributed crystal orientation.
2019, 50(1): 91-98
doi: 10.11777/j.issn1000-3304.2018.18156
Abstract:
The rheological behaviors of hydroxyethylacrylate/sodium acryloyldimethyl taurate copolymer (EMT-10) in aqueous solution have been investigated systematically. EMT-10 has been widely used as a cosmetics thickener for its excellent emulsibility/stability at relatively low content; besides, its capability of persistent thickening effect over a broad variety of novel chemical structures is conducive to their perfect compatibility with specific active ingredients. Both pyrene fluorescence observation and rheological behavior revealed that hydrogen bonding and electrostatic interactions could enhance the intramolecular hydrophobic associations among EMT-10 macromolecules in the solution system, which led to the formation of hydrophobic microdomains within EMT-10 molecules even at ultra-low concentration. In the meantime, EMT-10’s thickening capability could be promoted by the synergism of these three interactions, i.e., intermolecular hydrophobic associations, hydrogen bonding interaction, and electrostatic interaction. The viscosity of EMT-10 aqueous solution exhibited higher scaling value against concentration than neutral polymer and polyelectrolyte solutions did in the unentangled semidilute solution and entangled semidilute solution regions. Moreover, it was insensitive to temperature due to the counteracting effect between hydrophobic interaction and hydrogen bonding interaction. Yielding occurred when solution concentration was higher than 0.3 wt% and the yielding stress increased with mounting concentration. Dual yielding behaviors showed up at solution concentration above 1 wt%, of which the second yielding was related to the formation and breakup of clusters that resulted from intramolecular hydrophobic associations and hydrogen bonding interaction under high shearing. Various additives could affect the rheological behaviors of EMT-10 solution remarkably. Viscosity of 1.5 wt% EMT-10 solution decreased with the addition of surfactants, urea, and salt, among which salt exhibited a sharp reducing effect. Compared with poly(vinyl alcohol) and poly(ethylene oxide), EMT-10 implicated strong intermolecular interactions including chain entanglements, electrostatic interaction, hydrophobic interaction, and hydrogen bonding interaction.
The rheological behaviors of hydroxyethylacrylate/sodium acryloyldimethyl taurate copolymer (EMT-10) in aqueous solution have been investigated systematically. EMT-10 has been widely used as a cosmetics thickener for its excellent emulsibility/stability at relatively low content; besides, its capability of persistent thickening effect over a broad variety of novel chemical structures is conducive to their perfect compatibility with specific active ingredients. Both pyrene fluorescence observation and rheological behavior revealed that hydrogen bonding and electrostatic interactions could enhance the intramolecular hydrophobic associations among EMT-10 macromolecules in the solution system, which led to the formation of hydrophobic microdomains within EMT-10 molecules even at ultra-low concentration. In the meantime, EMT-10’s thickening capability could be promoted by the synergism of these three interactions, i.e., intermolecular hydrophobic associations, hydrogen bonding interaction, and electrostatic interaction. The viscosity of EMT-10 aqueous solution exhibited higher scaling value against concentration than neutral polymer and polyelectrolyte solutions did in the unentangled semidilute solution and entangled semidilute solution regions. Moreover, it was insensitive to temperature due to the counteracting effect between hydrophobic interaction and hydrogen bonding interaction. Yielding occurred when solution concentration was higher than 0.3 wt% and the yielding stress increased with mounting concentration. Dual yielding behaviors showed up at solution concentration above 1 wt%, of which the second yielding was related to the formation and breakup of clusters that resulted from intramolecular hydrophobic associations and hydrogen bonding interaction under high shearing. Various additives could affect the rheological behaviors of EMT-10 solution remarkably. Viscosity of 1.5 wt% EMT-10 solution decreased with the addition of surfactants, urea, and salt, among which salt exhibited a sharp reducing effect. Compared with poly(vinyl alcohol) and poly(ethylene oxide), EMT-10 implicated strong intermolecular interactions including chain entanglements, electrostatic interaction, hydrophobic interaction, and hydrogen bonding interaction.
