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2019 Volume 50 Issue 7
2019, 50(7): 653-670
doi: 10.11777/j.issn1000-3304.2019.19018
Abstract:
Porphyrins and their derivatives have attracted much attention due to their unique properties and various functions, and have been widely used in energy, catalysis and biomedical fields. Porphyrin-containing polymers possess both porphyrin and polymeric characteristics, which have also aroused great interest. On the basis of functional porphyrin units, the well-defined porphyrin-containing polymers not only have a clear and specific macromolecular structure, but also have been endowed with a variety of novel and unique features. By modifying the porphyrin units into the initiators, monomers or chain transfer agents, well-defined functional porphyrin-containing polymers with specific structures could be efficiently constructed by ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization or the combination of other strategies such as click chemistry. These well-defined porphyrin-containing polymers including telechelic polymers, alternating copolymers, block copolymers, star polymers, supramolecular polymers, can self-assemble to diverse morphologies such as spherical micelles, vesicles, nanorods and wormlike-structures and possess great potential in photodynamic therapy. Particularly, porphyrin-containing alternating copolymers can be obtained by RAFT copolymerization of 4-vinylbenzyl-terminated tetraphenylporphyrin and maleimide isobutyl polyhedral oligomeric silsesquioxane (POSS). The steric hindrance of POSS significantly reduces the π-π stacking of porphyrin units, which remarkably improve the singlet oxygen quantum yield and the photodynamic therapy efficacy.
Porphyrins and their derivatives have attracted much attention due to their unique properties and various functions, and have been widely used in energy, catalysis and biomedical fields. Porphyrin-containing polymers possess both porphyrin and polymeric characteristics, which have also aroused great interest. On the basis of functional porphyrin units, the well-defined porphyrin-containing polymers not only have a clear and specific macromolecular structure, but also have been endowed with a variety of novel and unique features. By modifying the porphyrin units into the initiators, monomers or chain transfer agents, well-defined functional porphyrin-containing polymers with specific structures could be efficiently constructed by ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization or the combination of other strategies such as click chemistry. These well-defined porphyrin-containing polymers including telechelic polymers, alternating copolymers, block copolymers, star polymers, supramolecular polymers, can self-assemble to diverse morphologies such as spherical micelles, vesicles, nanorods and wormlike-structures and possess great potential in photodynamic therapy. Particularly, porphyrin-containing alternating copolymers can be obtained by RAFT copolymerization of 4-vinylbenzyl-terminated tetraphenylporphyrin and maleimide isobutyl polyhedral oligomeric silsesquioxane (POSS). The steric hindrance of POSS significantly reduces the π-π stacking of porphyrin units, which remarkably improve the singlet oxygen quantum yield and the photodynamic therapy efficacy.
2019, 50(7): 671-684
doi: 10.11777/j.issn1000-3304.2019.19014
Abstract:
Graphene is an sp2 carbon material having a hexagonal honeycomb lattice in a single-layer two-dimensional (2D) plane due to its excellent properties such as high specific surface area, high electrical conductivity, good thermal stability and excellent mechanical properties. It has already aroused great research interest. Porous graphene refers to a carbon material possessing nano-scale pores in a two-dimensional plane. Due to the introduction of pores, not only the accumulation caused by π-π electron interaction is effectively avoided, but also some properties of the original graphene can be retained for porous graphene with higher specific surface area and pore volume. And also, the band gap of graphene was effectively opened. Therefore, it has great application prospects in the fields of optoelectronic devices, energy storage, gas separation/storage, wastewater separation and photocatalysis. At present, various porous graphene materials (for example, all-carbon porous graphene, doped porous graphene, and porous graphene composite materials, etc.) prepared by chemical synthesis, hydrothermal method, electrochemical reduction method, and template-oriented chemical vapor deposition (CVD) method, have been well applied in various fields. This paper aims to summarize the design and synthesis of various porous graphene materials, and also discusses the characteristics, advantages and disadvantages of porous graphene and various potential applications as well as the comparison of various porous graphene structures and properties. And looking forward to future research, it may focus on developing simpler, more convenient synthesis methods and how to accurately control the size, structure, and distribution density of pores in porous graphene, how to precisely control the type and distribution of doping elements, and how to better couple with other materials to obtain better composite materials, making porous graphene more excellent in various applications.
Graphene is an sp2 carbon material having a hexagonal honeycomb lattice in a single-layer two-dimensional (2D) plane due to its excellent properties such as high specific surface area, high electrical conductivity, good thermal stability and excellent mechanical properties. It has already aroused great research interest. Porous graphene refers to a carbon material possessing nano-scale pores in a two-dimensional plane. Due to the introduction of pores, not only the accumulation caused by π-π electron interaction is effectively avoided, but also some properties of the original graphene can be retained for porous graphene with higher specific surface area and pore volume. And also, the band gap of graphene was effectively opened. Therefore, it has great application prospects in the fields of optoelectronic devices, energy storage, gas separation/storage, wastewater separation and photocatalysis. At present, various porous graphene materials (for example, all-carbon porous graphene, doped porous graphene, and porous graphene composite materials, etc.) prepared by chemical synthesis, hydrothermal method, electrochemical reduction method, and template-oriented chemical vapor deposition (CVD) method, have been well applied in various fields. This paper aims to summarize the design and synthesis of various porous graphene materials, and also discusses the characteristics, advantages and disadvantages of porous graphene and various potential applications as well as the comparison of various porous graphene structures and properties. And looking forward to future research, it may focus on developing simpler, more convenient synthesis methods and how to accurately control the size, structure, and distribution density of pores in porous graphene, how to precisely control the type and distribution of doping elements, and how to better couple with other materials to obtain better composite materials, making porous graphene more excellent in various applications.
2019, 50(7): 685-694
doi: 10.11777/j.issn1000-3304.2018.18266
Abstract:
A series of red-emitting thermally activated delayed fluorescence (TADF) polymers based on poly(2,7-carbazole-co-3,3′ -dimethyldiphenyl ether) (PCzDMPE) main chains, including PCzDMPE-R03, PCzDMPE-R05, PCzDMPE-R07, and PCzDMPE-R10, have been designed and synthesized via Suzuki polycondensation. The thermally stable polymers possessed glass transition temperatures above 90 °C and decomposition temperatures above 410 °C, which is beneficial to the devices of long-term services. As the content of red TADF unit increased, the maximum emission was gradually red-shifted from 577 nm (PCzDMPE-R03) to 584 nm (PCzDMPE-R010), while the film photoluminescence quantum yield (PLQY) dropped correspondingly from 0.47 to 0.21 according to the energy gap law. Meanwhile, they all exhibited an obviously delayed fluorescence with the lifetime of 145 – 161 μs, accompanied by a prompt fluorescence of 4.5 – 6.5 ns. For instance, the temperature-dependent transient photoluminescence spectra measured for PCzDMPE-R07 sample displayed an enhanced delayed fluorescence upon the temperature rise from 150 K to 300 K, indicative of its TADF nature. More importantly, compared with earlier reports of red TADF polymers based on poly(fluorene-co-3,3′-dimethyl diphenyl ether), fluorene being replaced by carbazole in the present work could increase the highest occupied molecular orbital (HOMO) level and thus favor the hole injection. As a consequence, the turn-on voltage of PCzDMPE-R07 nondoped device was significantly reduced from 9.8 V to 5.2 V. PCzDMPE-R07 also outperformed the other candidates in terms of a maximum current efficiency of 3.35 cd/A and a maximum external quantum efficiency (EQE) of 2.03%. For performance optimization, a doped device was then fabricated by dispersing 20 wt% of PCzDMPE-R07 into the 1,3-bis(9H-carbazol-9-yl)benzene (mCP) matrix as an emitting layer. The corresponding current efficiency and EQE were further improved to 7.36 cd/A and 3.77%, respectively. To sum up, the copolymer containing carbazole and 3,3′-dimethyldiphenyl ether provides a favorable backbone framework for the design and synthesis of TADF polymers that possesses high efficiency and low driving voltage simultaneously.
A series of red-emitting thermally activated delayed fluorescence (TADF) polymers based on poly(2,7-carbazole-co-3,3′ -dimethyldiphenyl ether) (PCzDMPE) main chains, including PCzDMPE-R03, PCzDMPE-R05, PCzDMPE-R07, and PCzDMPE-R10, have been designed and synthesized via Suzuki polycondensation. The thermally stable polymers possessed glass transition temperatures above 90 °C and decomposition temperatures above 410 °C, which is beneficial to the devices of long-term services. As the content of red TADF unit increased, the maximum emission was gradually red-shifted from 577 nm (PCzDMPE-R03) to 584 nm (PCzDMPE-R010), while the film photoluminescence quantum yield (PLQY) dropped correspondingly from 0.47 to 0.21 according to the energy gap law. Meanwhile, they all exhibited an obviously delayed fluorescence with the lifetime of 145 – 161 μs, accompanied by a prompt fluorescence of 4.5 – 6.5 ns. For instance, the temperature-dependent transient photoluminescence spectra measured for PCzDMPE-R07 sample displayed an enhanced delayed fluorescence upon the temperature rise from 150 K to 300 K, indicative of its TADF nature. More importantly, compared with earlier reports of red TADF polymers based on poly(fluorene-co-3,3′-dimethyl diphenyl ether), fluorene being replaced by carbazole in the present work could increase the highest occupied molecular orbital (HOMO) level and thus favor the hole injection. As a consequence, the turn-on voltage of PCzDMPE-R07 nondoped device was significantly reduced from 9.8 V to 5.2 V. PCzDMPE-R07 also outperformed the other candidates in terms of a maximum current efficiency of 3.35 cd/A and a maximum external quantum efficiency (EQE) of 2.03%. For performance optimization, a doped device was then fabricated by dispersing 20 wt% of PCzDMPE-R07 into the 1,3-bis(9H-carbazol-9-yl)benzene (mCP) matrix as an emitting layer. The corresponding current efficiency and EQE were further improved to 7.36 cd/A and 3.77%, respectively. To sum up, the copolymer containing carbazole and 3,3′-dimethyldiphenyl ether provides a favorable backbone framework for the design and synthesis of TADF polymers that possesses high efficiency and low driving voltage simultaneously.
2019, 50(7): 695-701
doi: 10.11777/j.issn1000-3304.2018.18252
Abstract:
Magnetic PANI/P(St-NIPAM)/Fe3O4 particles with thermosensitive conductivity were prepared via two-step radical polymerization. Copolymerization of styrene (St) and N-isopropylacrylamide (NIPAM) was performed on the surface of modified magnetic ferroferric oxide (Fe3O4) to afford P(St-NIPAM)/Fe3O4 particles, and PANI/P(St-NIPAM)/Fe3O4 compounded particles were obtained thereafter from in situ oxidation polymerization of aniline inside the particles. Serial characterization including scanning electron microscopy (SEM), thermogravimetric analysis (TG), and infrared (IR) spectroscopy indicated that as-prepared particles possessed a core-shell structure, and the content of PANI in particles was closely related to the dosage of NIPAM in polymerization. In addition, dynamic light scattering (DLS) revealed the thermo-responsiveness of particle hydrodynamic diameter. Electrical conductivity of these magnetic particles was investigated in detail, and was found adjustable by the particle composition. Specifically, the conductivity of composite particle solution was enhanced from 58.4 μS/cm to 860 μS/cm when the monomer feed ratio was fixed during polymerization but the ratio of polymer shell to Fe3O4 was changed from 1:1 to 10:1. Meanwhile, the solution conductivity at 25 °C increased gradually from 698 μS/cm to 1120 μS/cm by raising the NIPAM/styrene ratio from 2 mol% to 10 mol% while keeping the ratio of Fe3O4 to total monomer amount at 1:10. Further measurement at 50 °C displayed a decreased conductivity for all PANI/P(St-NIPAM)/Fe3O4 particle solutions regardless of the varied NIPAM/styrene ratio, namely, the composite particles were proved with significant thermosensitivity in terms of their electrical conductivity. A relationship was thereby established between the temperature-sensitivity of particle conductivity and the thermal responsiveness of PNIPAM-induced volumetric change. These smart conductive particles bear huge potentials for extensive applications in biological imaging, sensing, and microelectronic devices.
Magnetic PANI/P(St-NIPAM)/Fe3O4 particles with thermosensitive conductivity were prepared via two-step radical polymerization. Copolymerization of styrene (St) and N-isopropylacrylamide (NIPAM) was performed on the surface of modified magnetic ferroferric oxide (Fe3O4) to afford P(St-NIPAM)/Fe3O4 particles, and PANI/P(St-NIPAM)/Fe3O4 compounded particles were obtained thereafter from in situ oxidation polymerization of aniline inside the particles. Serial characterization including scanning electron microscopy (SEM), thermogravimetric analysis (TG), and infrared (IR) spectroscopy indicated that as-prepared particles possessed a core-shell structure, and the content of PANI in particles was closely related to the dosage of NIPAM in polymerization. In addition, dynamic light scattering (DLS) revealed the thermo-responsiveness of particle hydrodynamic diameter. Electrical conductivity of these magnetic particles was investigated in detail, and was found adjustable by the particle composition. Specifically, the conductivity of composite particle solution was enhanced from 58.4 μS/cm to 860 μS/cm when the monomer feed ratio was fixed during polymerization but the ratio of polymer shell to Fe3O4 was changed from 1:1 to 10:1. Meanwhile, the solution conductivity at 25 °C increased gradually from 698 μS/cm to 1120 μS/cm by raising the NIPAM/styrene ratio from 2 mol% to 10 mol% while keeping the ratio of Fe3O4 to total monomer amount at 1:10. Further measurement at 50 °C displayed a decreased conductivity for all PANI/P(St-NIPAM)/Fe3O4 particle solutions regardless of the varied NIPAM/styrene ratio, namely, the composite particles were proved with significant thermosensitivity in terms of their electrical conductivity. A relationship was thereby established between the temperature-sensitivity of particle conductivity and the thermal responsiveness of PNIPAM-induced volumetric change. These smart conductive particles bear huge potentials for extensive applications in biological imaging, sensing, and microelectronic devices.
2019, 50(7): 702-709
doi: 10.11777/j.issn1000-3304.2018.18273
Abstract:
The effect of alkali metal counterion (Na+, K+, Cs+) on hierarchical self-assembly of C3-symmetric oligoamide supramolecules was studied by Synchrotron radiation X-ray small angle scattering and transmission electron microscope. The C3-symmetric molecules with three-armed aromatic oligoamide and different alkali metal counterions are denoted as P7(COONa)3, P7(COOK)3 and P7(COOCs)3. The experimental results show that the C3-symmetric molecules can self-assemble into tubular structures, which will further aggregate in aqueous solution to form a centered rectangular phase in P7(COONa)3, or a hexagonal phase in P7(COOK)3 and P7(COOCs)3. The centered rectangular phase formed by P7(COONa)3 has a higher degree of order and the adjacent tubular structures become closer compared with the hexagonal phase formed by P7(COOK)3 and P7(COOCs)3. Though the hexagonal phase formed by P7(COOCs)3 gives a higher degree of order than that formed by P7(COOK)3, they have the similar symmetry and comparable distances between adjacent tubular structures. Therefore, by changing the counterion from Na+ to K+ or Cs+, a phase transition from a centered rectangular phase to hexagonal phase can be achieved. In addition, the electron-density maps show that the fine structure of tubular aggregates will change slightly when the counterion changes from K+ to Cs+, which manifests the increase of the diameter of water channel in the tubular structures. The phase transition mentioned above may result from the different surface charge of tubular structures, as the adsorption capacity of counterions for the terminal carboxylate group in the C3-symmetric oligoamide will decline when the conterion changes from Na+ to Cs+ due to the increasing ionic radius. This kind of hierarchical self-assembly of ordered superstructure constructed by C3-symmetric oligoamide not only has the advantages of easy modification and structural stability, but also can be manipulated by simply changing the counterion, and thus has great application potential in drug delivery, tissue repair, etc.
The effect of alkali metal counterion (Na+, K+, Cs+) on hierarchical self-assembly of C3-symmetric oligoamide supramolecules was studied by Synchrotron radiation X-ray small angle scattering and transmission electron microscope. The C3-symmetric molecules with three-armed aromatic oligoamide and different alkali metal counterions are denoted as P7(COONa)3, P7(COOK)3 and P7(COOCs)3. The experimental results show that the C3-symmetric molecules can self-assemble into tubular structures, which will further aggregate in aqueous solution to form a centered rectangular phase in P7(COONa)3, or a hexagonal phase in P7(COOK)3 and P7(COOCs)3. The centered rectangular phase formed by P7(COONa)3 has a higher degree of order and the adjacent tubular structures become closer compared with the hexagonal phase formed by P7(COOK)3 and P7(COOCs)3. Though the hexagonal phase formed by P7(COOCs)3 gives a higher degree of order than that formed by P7(COOK)3, they have the similar symmetry and comparable distances between adjacent tubular structures. Therefore, by changing the counterion from Na+ to K+ or Cs+, a phase transition from a centered rectangular phase to hexagonal phase can be achieved. In addition, the electron-density maps show that the fine structure of tubular aggregates will change slightly when the counterion changes from K+ to Cs+, which manifests the increase of the diameter of water channel in the tubular structures. The phase transition mentioned above may result from the different surface charge of tubular structures, as the adsorption capacity of counterions for the terminal carboxylate group in the C3-symmetric oligoamide will decline when the conterion changes from Na+ to Cs+ due to the increasing ionic radius. This kind of hierarchical self-assembly of ordered superstructure constructed by C3-symmetric oligoamide not only has the advantages of easy modification and structural stability, but also can be manipulated by simply changing the counterion, and thus has great application potential in drug delivery, tissue repair, etc.
2019, 50(7): 710-720
doi: 10.11777/j.issn1000-3304.2018.18250
Abstract:
Waterborne polyurethane (WPU)/polydopamine (PDA) nanoparticle composites were successfully fabricated via in situ polymerization and effects of PDA nanoparticles on thermal properties, mechanical properties and anti-ultraviolet aging properties of WPU were investigated. Firstly, PDA nanoparticles with an average size of 150 nm were synthesized through spontaneous oxidation polymerization of dopamine hydrochloride in sodium hydroxide (NaOH) solution at 50 °C for 5 h under stirring. And it was retained in aqueous dispersion. Then, isophoeone diisocyanate (IPDI), polytetrahydrofuran diol (PTMG-1000), 2,2-dimethylol propionic acid (DMPA) were reacted to prepare the hydrophilic poliurethane prepolymer at 80 °C for 2 h under stirring, and then PDA nanoparticles in aqueous dispersion were added into the prepolymer to emulsify simultaneously for 30 min. Finally, 1,4-butanediol (BDO) was used as a small molecule chain extender to prepare WPU/PDA composites. It was found that both the thermostability and mechanical properties of WPU is enchanced by the addition of PDA nanoparticles. Especially when the concentration of PDA nanoparticles is 0.5 wt%, the initial degradation temperature of WPU/PDA composites is enhanced by 22.7 °C, and the tensile strength and Young’s modulus is increased by 37% and 78%, respectively, compared with pure WPU. Meanwhile, with the addition of PDA nanoparticles, the formation of cracks on the surface of WPU after ultraviolet irradiation is obviously hindered, and the decline of thermostability caused by ultraviolet irradiation is effectively suppressed. This can be mainly attributed to the impediment of the bond breakage during the ultraviolet irradiation due to the interaction of PDA nanoparticles with the urethane bonds and urea bonds of the hard segment of WPU.
Waterborne polyurethane (WPU)/polydopamine (PDA) nanoparticle composites were successfully fabricated via in situ polymerization and effects of PDA nanoparticles on thermal properties, mechanical properties and anti-ultraviolet aging properties of WPU were investigated. Firstly, PDA nanoparticles with an average size of 150 nm were synthesized through spontaneous oxidation polymerization of dopamine hydrochloride in sodium hydroxide (NaOH) solution at 50 °C for 5 h under stirring. And it was retained in aqueous dispersion. Then, isophoeone diisocyanate (IPDI), polytetrahydrofuran diol (PTMG-1000), 2,2-dimethylol propionic acid (DMPA) were reacted to prepare the hydrophilic poliurethane prepolymer at 80 °C for 2 h under stirring, and then PDA nanoparticles in aqueous dispersion were added into the prepolymer to emulsify simultaneously for 30 min. Finally, 1,4-butanediol (BDO) was used as a small molecule chain extender to prepare WPU/PDA composites. It was found that both the thermostability and mechanical properties of WPU is enchanced by the addition of PDA nanoparticles. Especially when the concentration of PDA nanoparticles is 0.5 wt%, the initial degradation temperature of WPU/PDA composites is enhanced by 22.7 °C, and the tensile strength and Young’s modulus is increased by 37% and 78%, respectively, compared with pure WPU. Meanwhile, with the addition of PDA nanoparticles, the formation of cracks on the surface of WPU after ultraviolet irradiation is obviously hindered, and the decline of thermostability caused by ultraviolet irradiation is effectively suppressed. This can be mainly attributed to the impediment of the bond breakage during the ultraviolet irradiation due to the interaction of PDA nanoparticles with the urethane bonds and urea bonds of the hard segment of WPU.
2019, 50(7): 721-729
doi: 10.11777/j.issn1000-3304.2019.19009
Abstract:
A series of reactive QACs with different chain lengths were prepared by inexpensive tertiary amine silane coupling agent, which were covalently grafted onto the surface of SiO2 nanoparticles in one step via a modified Stöber method. This method can increase the graft ratio of QAC relative to the use of dry silica powder. The structure and appearance of hybrid SiO2 nanoparticles were studied by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), zeta potential and thermogravimetric analysis (TGA). The antibacterial activity of hybrid SiO2 nanoparticles was evaluated by shake flask method. The composite films with excellent antimicrobial properties were obtained from a mixture of a polyurethane acrylate prepolymer and hybrid SiO2 nanoparticles via UV curing. The standard antibacterial test method ISO 22196 was used to evaluate the antibacterial properties of the film. The results showed that the hybrid SiO2 nanoparticles have a uniform particle size (~ 40 nm), a smooth spherical shape and a high positive charge on the surface. Antibacterial test results indicated that the hybrid SiO2 nanoparticles have excellent antibacterial activity compared with pure SiO2 nanoparticles, and can completely killed Escherichia coli and Staphylococcus epidermidis in 50 min. As the QAC alkyl chain grows, the antibacterial properties of the nanoparticles are further improved and SiO2-Q-12 can killed two bacteria completely within 20 min. This is mainly due to the hybrid SiO2 nanoparticles are light and have a high positive charge on the surface, so they can be quickly adsorbed on the surface of bacteria to achieve rapid sterilization. The hybrid SiO2 nanoparticles were enriched on the surface of the film. Adding a small amount (5 wt%) of hybrid SiO2 nanoparticles could endow the film with good antibacterial properties and high tensile strength. After the accelerated aging treatment of the composite film according to the national standard GB 15979-2002, it still possessed good antibacterial properties, indicating that the composite film has excellent antibacterial durability and stability. The test of the inhibition zone showed that the composite film was a contact antibacterial material, no antibacterial substance leaching, which was safer and more efficient.
A series of reactive QACs with different chain lengths were prepared by inexpensive tertiary amine silane coupling agent, which were covalently grafted onto the surface of SiO2 nanoparticles in one step via a modified Stöber method. This method can increase the graft ratio of QAC relative to the use of dry silica powder. The structure and appearance of hybrid SiO2 nanoparticles were studied by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), zeta potential and thermogravimetric analysis (TGA). The antibacterial activity of hybrid SiO2 nanoparticles was evaluated by shake flask method. The composite films with excellent antimicrobial properties were obtained from a mixture of a polyurethane acrylate prepolymer and hybrid SiO2 nanoparticles via UV curing. The standard antibacterial test method ISO 22196 was used to evaluate the antibacterial properties of the film. The results showed that the hybrid SiO2 nanoparticles have a uniform particle size (~ 40 nm), a smooth spherical shape and a high positive charge on the surface. Antibacterial test results indicated that the hybrid SiO2 nanoparticles have excellent antibacterial activity compared with pure SiO2 nanoparticles, and can completely killed Escherichia coli and Staphylococcus epidermidis in 50 min. As the QAC alkyl chain grows, the antibacterial properties of the nanoparticles are further improved and SiO2-Q-12 can killed two bacteria completely within 20 min. This is mainly due to the hybrid SiO2 nanoparticles are light and have a high positive charge on the surface, so they can be quickly adsorbed on the surface of bacteria to achieve rapid sterilization. The hybrid SiO2 nanoparticles were enriched on the surface of the film. Adding a small amount (5 wt%) of hybrid SiO2 nanoparticles could endow the film with good antibacterial properties and high tensile strength. After the accelerated aging treatment of the composite film according to the national standard GB 15979-2002, it still possessed good antibacterial properties, indicating that the composite film has excellent antibacterial durability and stability. The test of the inhibition zone showed that the composite film was a contact antibacterial material, no antibacterial substance leaching, which was safer and more efficient.
2019, 50(7): 730-739
doi: 10.11777/j.issn1000-3304.2018.18271
Abstract:
Poly(urea-siloxane) (PUS) was prepared through the precipitation polymerization between α,ω-aminopropyl disiloxane (APDS) and toluene diisocyanate (TDI) in H2O-acetone mixed solvent, which involved no extra addition of surfactants, initiators, or any other additives. Effects of monomer ratio (APDS/TDI, W/W), binary solvent composition ratio (H2O/acetone, W/W), and reaction temperature on the polymerization process and PUS morphology were investigated. Results indicated that tuning the APDS/TDI ratio could readily change the PUS morphology from a porous irregular form into porous microspheres. Specifically, the former appeared at APDS/TDI weight ratio no more than 2/8, while the latter occurred when increasing the APDS/TDI ratio up to 3/7 or higher; APDS/TDI ratio at 4/6 could affard porous PUS microspheres with 1 µm in diameter and narrow polydispersity. On the other hand, H2O/acetone weight ratio and polymerization temperature also affected the size and size distribution of PUS microspheres remarkably, and the the narrowest size distribution of 1.04 was realized at APDS/TDI ratio of 4/6, H2O/acetone ratio of 3/7, and polymerization temperature equal to 30 °C. With APDS/TDI ratio varied from 0/10 to 4/6, the pore volume of PUS increased from about 1.79 cm3/g to 2.36 cm3/g, whereas the specific surface area decreased from about 163.00 m2/g to 106.18 m2/g. On the basis of polymerization process, the changes in PUS morphology and porous properties versus APDS/TDI ratio variation could be well interpreted through the mechanisms of polymer precipitation and pore formation. PUS chemical structure was revealed by FTIR and NMR, while thermal property characterization indicated an enhanced thermal stability with the incorporation of APDS units into polyurea system.
Poly(urea-siloxane) (PUS) was prepared through the precipitation polymerization between α,ω-aminopropyl disiloxane (APDS) and toluene diisocyanate (TDI) in H2O-acetone mixed solvent, which involved no extra addition of surfactants, initiators, or any other additives. Effects of monomer ratio (APDS/TDI, W/W), binary solvent composition ratio (H2O/acetone, W/W), and reaction temperature on the polymerization process and PUS morphology were investigated. Results indicated that tuning the APDS/TDI ratio could readily change the PUS morphology from a porous irregular form into porous microspheres. Specifically, the former appeared at APDS/TDI weight ratio no more than 2/8, while the latter occurred when increasing the APDS/TDI ratio up to 3/7 or higher; APDS/TDI ratio at 4/6 could affard porous PUS microspheres with 1 µm in diameter and narrow polydispersity. On the other hand, H2O/acetone weight ratio and polymerization temperature also affected the size and size distribution of PUS microspheres remarkably, and the the narrowest size distribution of 1.04 was realized at APDS/TDI ratio of 4/6, H2O/acetone ratio of 3/7, and polymerization temperature equal to 30 °C. With APDS/TDI ratio varied from 0/10 to 4/6, the pore volume of PUS increased from about 1.79 cm3/g to 2.36 cm3/g, whereas the specific surface area decreased from about 163.00 m2/g to 106.18 m2/g. On the basis of polymerization process, the changes in PUS morphology and porous properties versus APDS/TDI ratio variation could be well interpreted through the mechanisms of polymer precipitation and pore formation. PUS chemical structure was revealed by FTIR and NMR, while thermal property characterization indicated an enhanced thermal stability with the incorporation of APDS units into polyurea system.
2019, 50(7): 740-751
doi: 10.11777/j.issn1000-3304.2018.18257
Abstract:
The flame retardancy of poly(lactic acid) (PLA) was for the first time improved by a synergistic effect between octaphenyl silsesquioxane (OPS) the organic-inorganic hybrid and ammonium polyphosphate (APP) the inorganic phosphorus-based flame retardant. PLA/OPS, PLA/APP, and PLA/OPS+APP composites fabricated by twin-screw melt blending were subjected to a series of characterizations, including vertical test, cone calorimetry, and limiting oxygen index measurements. Remarkable enhancement was achieved for the flame retardant properties of PLA/OPS+APP, as OPS and APP could reduce synergistically the heat release rate (HRR) of PLA. Dispersion of OPS and APP in the PLA matrix was observed by scanning electron microscopy (SEM), while thermal stability of the composites prepared was studied via thermogravimetric analysis (TGA). For an in-depth understanding of the combustion process, morphology and elemental composition of the char residues after cone calorimetry test were further investigated through SEM, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Results showed that both OPS and APP were uniformly distributed in the PLA matrix. Besides, the initial decomposition processes of APP and PLA were in good accordance with each other, while the thermal decomposition process of OPS agreed well with that of APP at high temperature; such matching decomposition processes and synergism between OPS and APP gave rise to an improved thermal stability of the PLA composites prepared. Apart from the reduction of HRR peak, OPS/APP synergy could diminish significantly the retardant-induced smoke release while maintaining a satisfactory tensile performance for the PLA material. Finally, underlying mechanisms of the specific combustion process were tentatively proposed for the three kinds of flame-retardant PLA composites.
The flame retardancy of poly(lactic acid) (PLA) was for the first time improved by a synergistic effect between octaphenyl silsesquioxane (OPS) the organic-inorganic hybrid and ammonium polyphosphate (APP) the inorganic phosphorus-based flame retardant. PLA/OPS, PLA/APP, and PLA/OPS+APP composites fabricated by twin-screw melt blending were subjected to a series of characterizations, including vertical test, cone calorimetry, and limiting oxygen index measurements. Remarkable enhancement was achieved for the flame retardant properties of PLA/OPS+APP, as OPS and APP could reduce synergistically the heat release rate (HRR) of PLA. Dispersion of OPS and APP in the PLA matrix was observed by scanning electron microscopy (SEM), while thermal stability of the composites prepared was studied via thermogravimetric analysis (TGA). For an in-depth understanding of the combustion process, morphology and elemental composition of the char residues after cone calorimetry test were further investigated through SEM, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. Results showed that both OPS and APP were uniformly distributed in the PLA matrix. Besides, the initial decomposition processes of APP and PLA were in good accordance with each other, while the thermal decomposition process of OPS agreed well with that of APP at high temperature; such matching decomposition processes and synergism between OPS and APP gave rise to an improved thermal stability of the PLA composites prepared. Apart from the reduction of HRR peak, OPS/APP synergy could diminish significantly the retardant-induced smoke release while maintaining a satisfactory tensile performance for the PLA material. Finally, underlying mechanisms of the specific combustion process were tentatively proposed for the three kinds of flame-retardant PLA composites.
2019, 50(7): 752-760
doi: 10.11777/j.issn1000-3304.2018.18261
Abstract:
The poly(vinylidene fluoride) (PVDF) as-spun fibers with different spin-stretching ratios were fabricated via melt-spinning method using plunger spinning machine. PVDF fibers with different post-stretching ratios were subsequently obtained by post-stretching method under the thermal treatment condition. The crystal and orientation structure of the fibers were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and so on. The results indicated the orientation of α crystal and macromolecular increased with the increasing spin-stretching ratio. Furthermore, as the higher spin-stretching ratio increased, the degree of crystallinity of as-spun fiber was prone to perfection. Furthermore, according to the POM photomicrograph, the horizon of extinction position was almost entirely black, and the horizon of diagonal position was getting brighter, due to the increase of the anisotropy of as-spun fibers. This was attributed that the irregular fiber macromolecules were stretched to regular structure. When spin-stretching ratio was 330, the crystallinity of as-spun fiber could reach 56.38% and the orientation factor of α(110/200) crystal plane was up to 0.89. In terms of post-stretching technique, the stretching ratios had no significant influence on the degree of crystallinity. However, the post-stretching process played a positive role in the transition of the crystal phase from α to β. The molecular chains of the fibers are easier to slip and arrange regularly along the fiber axis during spin-stretching process. The conformation was easier to transfer from α phase to β phase owing to the segmental motion of molecular chains during post-stretching process. Especially, the orientation of β crystal was also improved at the same time. Specially, when the post-stretching was up to the stage of uniform reduction of fiber diameter, the orientation of β crystal retained a high level. When post-stretching ratio was 11, the content of β crystal could account for 82.85% and the orientation factor of β(110/200) crystal plane was up to 0.83.
The poly(vinylidene fluoride) (PVDF) as-spun fibers with different spin-stretching ratios were fabricated via melt-spinning method using plunger spinning machine. PVDF fibers with different post-stretching ratios were subsequently obtained by post-stretching method under the thermal treatment condition. The crystal and orientation structure of the fibers were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and so on. The results indicated the orientation of α crystal and macromolecular increased with the increasing spin-stretching ratio. Furthermore, as the higher spin-stretching ratio increased, the degree of crystallinity of as-spun fiber was prone to perfection. Furthermore, according to the POM photomicrograph, the horizon of extinction position was almost entirely black, and the horizon of diagonal position was getting brighter, due to the increase of the anisotropy of as-spun fibers. This was attributed that the irregular fiber macromolecules were stretched to regular structure. When spin-stretching ratio was 330, the crystallinity of as-spun fiber could reach 56.38% and the orientation factor of α(110/200) crystal plane was up to 0.89. In terms of post-stretching technique, the stretching ratios had no significant influence on the degree of crystallinity. However, the post-stretching process played a positive role in the transition of the crystal phase from α to β. The molecular chains of the fibers are easier to slip and arrange regularly along the fiber axis during spin-stretching process. The conformation was easier to transfer from α phase to β phase owing to the segmental motion of molecular chains during post-stretching process. Especially, the orientation of β crystal was also improved at the same time. Specially, when the post-stretching was up to the stage of uniform reduction of fiber diameter, the orientation of β crystal retained a high level. When post-stretching ratio was 11, the content of β crystal could account for 82.85% and the orientation factor of β(110/200) crystal plane was up to 0.83.
