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2019 Volume 50 Issue 2
2019, 50(2):
Abstract:
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2019, 50(2): 99-101
doi: 10.11777/j.issn1000-3304.2019.19006
Abstract:
Polypeptides (α-amino acid polymers), as one of the most promising biomedical polymers, have excellent biocompatibility, bioactivities and biodegradability. Primary amine-initiated NCA polymerization is the most widely used method to prepare polypeptides. However, this polymerization is super sensitive to moisture, with slow reaction rate and side reactions, and difficult to obtain polypeptides with high molecular weight. Recently, Prof. Liu et al. at East China University of Science and Technology utilized Lithium Hexamethyldisilazide (LiHMDS) as the catalyst to initiate ring opening polymerization of NCA. This is the first demonstration of moisture insensitive NCA polymerization under atmosphere condition. This NCA polymerization can be completed within a few minutes to a few hours and successfully produces poly-BLG with number average molecular weight over 2.8 × 105 g/mol. This research opens the era for easy and efficient synthesis of polypeptides and builds the foundation for large-scale application of polypeptides as biomedical materials.
Polypeptides (α-amino acid polymers), as one of the most promising biomedical polymers, have excellent biocompatibility, bioactivities and biodegradability. Primary amine-initiated NCA polymerization is the most widely used method to prepare polypeptides. However, this polymerization is super sensitive to moisture, with slow reaction rate and side reactions, and difficult to obtain polypeptides with high molecular weight. Recently, Prof. Liu et al. at East China University of Science and Technology utilized Lithium Hexamethyldisilazide (LiHMDS) as the catalyst to initiate ring opening polymerization of NCA. This is the first demonstration of moisture insensitive NCA polymerization under atmosphere condition. This NCA polymerization can be completed within a few minutes to a few hours and successfully produces poly-BLG with number average molecular weight over 2.8 × 105 g/mol. This research opens the era for easy and efficient synthesis of polypeptides and builds the foundation for large-scale application of polypeptides as biomedical materials.
2019, 50(2): 102-108
doi: 10.11777/j.issn1000-3304.2018.18236
Abstract:
Near-infrared (NIR) light occupies a large proportion of sunlight and possesses unique advantages of deep penetration into biological tissues and high maximum permissible exposure to the laser. Therefore, the utilization of NIR light is of great significance in the areas of energy, medical imaging, and photo-therapy. However, the utilization of near-infrared light based on traditional mechanisms, such as photochemistry and photoelectricity, is usually very low owing to the fast vibrational relaxation and internal transformation in these wave ranges. Upconversion and two-photon absorption can convert NIR light into light with shorter wavelength but these two methods often rely on high-power light source irradiation, and the conversion efficiency of NIR light is low. On the basis of the mechanism of non-irradiation transition, polymer-based photothermal conversion plays a novel role in efficient utilization of NIR light. In this work, recent progresses of our group in the applications of near-infrared photothermal conversion materials, especially polymer materials, are reviewed. Firstly, the concept of photoannealing is proposed on the basis of photothermal conversion. In contrast to the conventional annealing process, such as solvent annealing and thermal annealing, photoanealing process of polymer has the advantages of good spatial selectivity and biocompatibility. It has been applied to the remote control of particle shape, volume, and porosity in organism, which can serve as a powerful tool for the noninvasive treatment. Besides, flexible, self-repairing, and highly sensitive near-infrared light sensors are prepared by combining photothermal materials with thermal fluids. The resultant NIR sensing fluids have better sensitivity than the commercial NIR sensing semiconductor does, and they can be combined with the inkjet printing technology to achieve low-cost production with high throughput. Finally, the conjugated polymer with multiple intramolecular hydrogen bonds and Donor-Acceptor structure is designed to achieve good absorption in the NIR-II region, which has deeper penetration than light in NIR-I region does. This special polymer has been used for remote power supply for implantable electronic devices through energy coupling.
Near-infrared (NIR) light occupies a large proportion of sunlight and possesses unique advantages of deep penetration into biological tissues and high maximum permissible exposure to the laser. Therefore, the utilization of NIR light is of great significance in the areas of energy, medical imaging, and photo-therapy. However, the utilization of near-infrared light based on traditional mechanisms, such as photochemistry and photoelectricity, is usually very low owing to the fast vibrational relaxation and internal transformation in these wave ranges. Upconversion and two-photon absorption can convert NIR light into light with shorter wavelength but these two methods often rely on high-power light source irradiation, and the conversion efficiency of NIR light is low. On the basis of the mechanism of non-irradiation transition, polymer-based photothermal conversion plays a novel role in efficient utilization of NIR light. In this work, recent progresses of our group in the applications of near-infrared photothermal conversion materials, especially polymer materials, are reviewed. Firstly, the concept of photoannealing is proposed on the basis of photothermal conversion. In contrast to the conventional annealing process, such as solvent annealing and thermal annealing, photoanealing process of polymer has the advantages of good spatial selectivity and biocompatibility. It has been applied to the remote control of particle shape, volume, and porosity in organism, which can serve as a powerful tool for the noninvasive treatment. Besides, flexible, self-repairing, and highly sensitive near-infrared light sensors are prepared by combining photothermal materials with thermal fluids. The resultant NIR sensing fluids have better sensitivity than the commercial NIR sensing semiconductor does, and they can be combined with the inkjet printing technology to achieve low-cost production with high throughput. Finally, the conjugated polymer with multiple intramolecular hydrogen bonds and Donor-Acceptor structure is designed to achieve good absorption in the NIR-II region, which has deeper penetration than light in NIR-I region does. This special polymer has been used for remote power supply for implantable electronic devices through energy coupling.
2019, 50(2): 109-117
doi: 10.11777/j.issn1000-3304.2018.18231
Abstract:
A new protocol for conjugated polymer synthesis, direct arylation polycondensation (DArP) bears the merits of more straightforwardness (fewer steps), better atom economy, and greater environmental benignity, but still faces remaining challenges in reactivity and selectivity. Given that high mobility conjugated polymers are receiving added attention these days due to their extensive use in organic thin-film transistors (OTFTs), this feature article briefly introduces the underlying mechanism of direct arylation reaction and systematically summarizes the application of DArP in synthesizing polythiophenes and donor-acceptor (D-A) conjugated polymers from naphthalene diimide (NDI), diketopyrrolopyrrole (DPP), and isoindigo (IID) derivatives. The α C―H direct arylation of thiophene rings can give rise to conjugated polymers based on NDI and DPP derivatives, which exhibit negligible defects and reasonably high molecular weights through careful optimization of the catalyst (including ligands), solvent, additives, monomer concentration, and polymerization temperature. To deal with side reactions during DArP, primarily the C―H/C―H and C―Br/C―Br homo-couplings and the β C―H direct arylation (causing branching or cross-linking), multi-fluorinated thiophene moieties such as 3,3',4,4'-tetrafluoro-2,2'-bithiophene (4F2T) and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT) have been designed for a higher reactivity toward DArP. Moreover, selectivity issues can be well sidestepped by introducing F-atoms onto the β-positions of thiophene unit, which in the meantime significantly lowers the frontier molecular orbital energy levels of polymers obtained. In consequence, ambipolar or unipolar n-type D-A conjugated polymers based on DPP and IID derivatives can be harvested at high molecular weight, which enables further fabrication of ambipolar OTFTs with hole and electron mobilities individually up to 2.63 and 8.11 cm2 V−1 s−1 or unipolar n-type OTFTs with electron mobility over 4 cm2 V−1 s−1. Progress above indicates that DArP can afford high mobility and defect-free conjugated polymers through elaborate monomer design and the optimal polymerization conditions. Hence, DArP can serve as a reliable method for the mass production of high performance conjugated polymers.
A new protocol for conjugated polymer synthesis, direct arylation polycondensation (DArP) bears the merits of more straightforwardness (fewer steps), better atom economy, and greater environmental benignity, but still faces remaining challenges in reactivity and selectivity. Given that high mobility conjugated polymers are receiving added attention these days due to their extensive use in organic thin-film transistors (OTFTs), this feature article briefly introduces the underlying mechanism of direct arylation reaction and systematically summarizes the application of DArP in synthesizing polythiophenes and donor-acceptor (D-A) conjugated polymers from naphthalene diimide (NDI), diketopyrrolopyrrole (DPP), and isoindigo (IID) derivatives. The α C―H direct arylation of thiophene rings can give rise to conjugated polymers based on NDI and DPP derivatives, which exhibit negligible defects and reasonably high molecular weights through careful optimization of the catalyst (including ligands), solvent, additives, monomer concentration, and polymerization temperature. To deal with side reactions during DArP, primarily the C―H/C―H and C―Br/C―Br homo-couplings and the β C―H direct arylation (causing branching or cross-linking), multi-fluorinated thiophene moieties such as 3,3',4,4'-tetrafluoro-2,2'-bithiophene (4F2T) and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT) have been designed for a higher reactivity toward DArP. Moreover, selectivity issues can be well sidestepped by introducing F-atoms onto the β-positions of thiophene unit, which in the meantime significantly lowers the frontier molecular orbital energy levels of polymers obtained. In consequence, ambipolar or unipolar n-type D-A conjugated polymers based on DPP and IID derivatives can be harvested at high molecular weight, which enables further fabrication of ambipolar OTFTs with hole and electron mobilities individually up to 2.63 and 8.11 cm2 V−1 s−1 or unipolar n-type OTFTs with electron mobility over 4 cm2 V−1 s−1. Progress above indicates that DArP can afford high mobility and defect-free conjugated polymers through elaborate monomer design and the optimal polymerization conditions. Hence, DArP can serve as a reliable method for the mass production of high performance conjugated polymers.
2019, 50(2): 118-123
doi: 10.11777/j.issn1000-3304.2018.18180
Abstract:
Poly(styrene oxide) (PSO) macromonomers were synthesized in one step through the anionic ring-opening polymerization (ROP) of styrene oxide (SO) at room temperature, with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2Ʌ5,4Ʌ5-catenadi-(phosphazene) (t-BuP4) as the catalyst, and 4-vinylbenzyl alcohol (VBA) as the functional initiator. The copolymerization of PSO macromonomers and methyl methacrylate (MMA) was carried out at different temperatures through free radical co-polymerization to prepare graft copolymers. The structures and properties of the functional initiator, the obtained macromonomers and the grafted copolymers were characterized by nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results showed that functional initiator VBA was synthesized successfully. Super base t-BuP4 displayed high catalytic activity for the ring-opening polymerization of SO, resulting in PSO macromonomers with polymerizable vinyl group, controlled molecular weight (Mn = 2700 – 11300 g/mol), and narrow molecular weight distribution (< 1.19). NMR measurement confirmed that the copolymerization of PSO macromonomers and MMA was carried out successfully to produce grafted copolymers. With the increase of copolymerization temperature, the conversion of MMA increased (> 96%), while the molecular weight of the copolymers decreased and the molecular weight distribution became narrow. The GPC curves of the product for the copolymerization before precipitation were bimodal, the molecular weight of the obtained polymers was low (6200 – 7800 g/mol) and the molecular weight distribution was wide (6.39 – 10.41). After precipitation, the GPC curves showed a unimodal signal, the molecular weight became larger (4.33 × 10 4 – 5.95 × 10 4 g/mol) and the molecular weight distribution became narrower (1.46 – 1.62). Integral calculation of the GPC curves and NMR measurement confirmed that there were about 3.8% – 4.6% inert components in the synthesized macromonomers. For the thermal analysis of PSO, PMMA- g-PSO and PMMA, the glass transition temperature (Tg) measured by DSC showed that the prepared grafted copolymer had only one Tg, which was in good accordance with the theoretical value calculated according to the Fox equation. This result further proved that the graft copolymers were successfully prepared.
Poly(styrene oxide) (PSO) macromonomers were synthesized in one step through the anionic ring-opening polymerization (ROP) of styrene oxide (SO) at room temperature, with 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2Ʌ5,4Ʌ5-catenadi-(phosphazene) (t-BuP4) as the catalyst, and 4-vinylbenzyl alcohol (VBA) as the functional initiator. The copolymerization of PSO macromonomers and methyl methacrylate (MMA) was carried out at different temperatures through free radical co-polymerization to prepare graft copolymers. The structures and properties of the functional initiator, the obtained macromonomers and the grafted copolymers were characterized by nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results showed that functional initiator VBA was synthesized successfully. Super base t-BuP4 displayed high catalytic activity for the ring-opening polymerization of SO, resulting in PSO macromonomers with polymerizable vinyl group, controlled molecular weight (Mn = 2700 – 11300 g/mol), and narrow molecular weight distribution (< 1.19). NMR measurement confirmed that the copolymerization of PSO macromonomers and MMA was carried out successfully to produce grafted copolymers. With the increase of copolymerization temperature, the conversion of MMA increased (> 96%), while the molecular weight of the copolymers decreased and the molecular weight distribution became narrow. The GPC curves of the product for the copolymerization before precipitation were bimodal, the molecular weight of the obtained polymers was low (6200 – 7800 g/mol) and the molecular weight distribution was wide (6.39 – 10.41). After precipitation, the GPC curves showed a unimodal signal, the molecular weight became larger (4.33 × 10 4 – 5.95 × 10 4 g/mol) and the molecular weight distribution became narrower (1.46 – 1.62). Integral calculation of the GPC curves and NMR measurement confirmed that there were about 3.8% – 4.6% inert components in the synthesized macromonomers. For the thermal analysis of PSO, PMMA- g-PSO and PMMA, the glass transition temperature (Tg) measured by DSC showed that the prepared grafted copolymer had only one Tg, which was in good accordance with the theoretical value calculated according to the Fox equation. This result further proved that the graft copolymers were successfully prepared.
2019, 50(2): 124-134
doi: 10.11777/j.issn1000-3304.2018.18187
Abstract:
Eight [N,P]-type non-metallocene catalysts were synthesized successfully via the reaction between two kinds of ligands carrying different electronic effect groups and chloride compounds of transition metals Ti, Zr, Ni and Pd. Catalyst Cat.L2-Ti exhibited the highest catalytic activity toward ethylene/propylene copolymerization thanks to the combined effects exerted by ligand structure, central atomic species, and polymerization conditions on copolymerization behavior of ethylene with propylene. The copolymer product achieved a high Mw up to 2.75 × 105 g/mol as measured by GPC, and 13C-NMR test suggested that the content of propylene insertion within copolymer backbone reached 11.5 mol%. Characterization with 13C-NMR, DSC, and WAXD demonstrated that macromolecular chains of the obtained copolymer were composed mainly of ethylene units existing as long-chain segments, while some other ethylene units formed random segments with copolymerized propylene monomers. Melting point of the copolymer decreased along with the increasing amount of propylene insertion, and so did the peak intensity in crystal diffraction of polyethylene segments. At the greatest insertion amount of propylene of 11.5 mol%, the melting peak could hardly be noted on DSC curve, and the peak intensity in crystal diffraction weakened markedly as well. Moreover, neither the characteristic peak in FTIR spectra nor the diffraction peak on WAXD patterns showed up for the long segments of polypropylene. Together with the missing melting peak of isotactic polypropylene on DSC curve, it was inferred that polypropylene hardly existed in the long-chain form basically. All these results confirmed the effective role played by [N,P]-type non-metallocene catalysts in the preparation of multi-block copolymers PE-b-P(E/P).
Eight [N,P]-type non-metallocene catalysts were synthesized successfully via the reaction between two kinds of ligands carrying different electronic effect groups and chloride compounds of transition metals Ti, Zr, Ni and Pd. Catalyst Cat.L2-Ti exhibited the highest catalytic activity toward ethylene/propylene copolymerization thanks to the combined effects exerted by ligand structure, central atomic species, and polymerization conditions on copolymerization behavior of ethylene with propylene. The copolymer product achieved a high Mw up to 2.75 × 105 g/mol as measured by GPC, and 13C-NMR test suggested that the content of propylene insertion within copolymer backbone reached 11.5 mol%. Characterization with 13C-NMR, DSC, and WAXD demonstrated that macromolecular chains of the obtained copolymer were composed mainly of ethylene units existing as long-chain segments, while some other ethylene units formed random segments with copolymerized propylene monomers. Melting point of the copolymer decreased along with the increasing amount of propylene insertion, and so did the peak intensity in crystal diffraction of polyethylene segments. At the greatest insertion amount of propylene of 11.5 mol%, the melting peak could hardly be noted on DSC curve, and the peak intensity in crystal diffraction weakened markedly as well. Moreover, neither the characteristic peak in FTIR spectra nor the diffraction peak on WAXD patterns showed up for the long segments of polypropylene. Together with the missing melting peak of isotactic polypropylene on DSC curve, it was inferred that polypropylene hardly existed in the long-chain form basically. All these results confirmed the effective role played by [N,P]-type non-metallocene catalysts in the preparation of multi-block copolymers PE-b-P(E/P).
Micro Rings Self-assembled by Fluorescent Fusion-protein Based on Multiple Non-covalent Interactions
2019, 50(2): 135-146
doi: 10.11777/j.issn1000-3304.2018.18204
Abstract:
Proteins are attractive building blocks for construction of variant functional materials because of their chemical and structural diversities, and intrinsic functions. As the industry of biotechnology continues to expand, so does the expression of recombinant proteins with wide varieties. In this work, we adopted the recombinant protein technique to construct a new fusion protein, GFP-SA, as the building block of self-assemblies. The purification of GFP-SA was characterized by Superdex 75 size exclusive chromatography, SDS-PAGE, and MALDI-TOF. Then, GPC and native-PAGE were used to characterize the dimerization of GFP-SA based on the hydrogen bonds between neighboring SAs. Furthermore, ITC was employed to test the binding ability between GFP-SA and biotin, which revealed KD = 0.24 μmol/L. In this study, we also designed and successfully synthesized the ligand RhYBio2, which is composed of two biotin molecules and one rhodamine B molecule. The size of GFP-SA increased rapidly to 370 nm within one minute after mixing with RhYBio2. We measured the particle size of GFP-SA/RhYBio2 mixture every few minutes until the size stabilized at around 1300 nm 2 h later. However, size variation was barely observed for the controlled samples of SA/RhYBio2 (controlled protein) and GFP-SA/YBio (controlled ligand). We hypothesized that the two biotin molecules of RhYBio2 could bind specifically with SA and align GFP-SA/RhYBio2 into nanowires, which assembled further into micro rings. Their size was measured by dynamic light scattering (DLS) while the morphology was observed intuitively on a transmission electron microscope (TEM) and a confocal microscope (CM). The characteristic results from TEM and CM suggested an uneven size distribution of the micro rings prepared, which might be attributable to the flexibility of the fusion protein GFP-SA. These micro rings of GFP-SA/RhYBio2 with fluorescence has great potential for biological applications.
Proteins are attractive building blocks for construction of variant functional materials because of their chemical and structural diversities, and intrinsic functions. As the industry of biotechnology continues to expand, so does the expression of recombinant proteins with wide varieties. In this work, we adopted the recombinant protein technique to construct a new fusion protein, GFP-SA, as the building block of self-assemblies. The purification of GFP-SA was characterized by Superdex 75 size exclusive chromatography, SDS-PAGE, and MALDI-TOF. Then, GPC and native-PAGE were used to characterize the dimerization of GFP-SA based on the hydrogen bonds between neighboring SAs. Furthermore, ITC was employed to test the binding ability between GFP-SA and biotin, which revealed KD = 0.24 μmol/L. In this study, we also designed and successfully synthesized the ligand RhYBio2, which is composed of two biotin molecules and one rhodamine B molecule. The size of GFP-SA increased rapidly to 370 nm within one minute after mixing with RhYBio2. We measured the particle size of GFP-SA/RhYBio2 mixture every few minutes until the size stabilized at around 1300 nm 2 h later. However, size variation was barely observed for the controlled samples of SA/RhYBio2 (controlled protein) and GFP-SA/YBio (controlled ligand). We hypothesized that the two biotin molecules of RhYBio2 could bind specifically with SA and align GFP-SA/RhYBio2 into nanowires, which assembled further into micro rings. Their size was measured by dynamic light scattering (DLS) while the morphology was observed intuitively on a transmission electron microscope (TEM) and a confocal microscope (CM). The characteristic results from TEM and CM suggested an uneven size distribution of the micro rings prepared, which might be attributable to the flexibility of the fusion protein GFP-SA. These micro rings of GFP-SA/RhYBio2 with fluorescence has great potential for biological applications.
2019, 50(2): 147-159
doi: 10.11777/j.issn1000-3304.2018.18176
Abstract:
Lignin a commonly used modifier for bio-based PLA materials due to its good biodegradability, structural stability, and the nature of biomacromolecule. However, the poor compatibility between neat lignin and PLA matrix compromises greatly its further application. To this end, lignin-g-polyester with two different molecular structures, i.e. lignin-g-PDVL-ran-PLLA and lignin-g-PDVL-b-PLLA, were specially designed for compatibility improvement and successfully synthesized via ring-opening polymerization with δ-valerolactone (DVL) and L-lactone (L-LA). PDVL as a soft component could reduce the brittleness of PLA with its long polymer chains while L-LA would enhance the compatibility between lignin nanofillers and PLA matrix due to the structural similarity with PLA. Lignin-g-polyester fillers with various segment structures were prepared by tuning the monomer ratio, and a series of PLA/lignin-g-polyester composites with different filler contents were further fabricated via the solution casting method. Structures of lignin-g-polyester were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR), while the uniform dispersion of lignin-g-polyester fillers in PLA composites was verified by field emission scanning electron microscopy (FE-SEM). Differential scanning calorimetry (DSC) was utilized to study the thermal properties and crystallization behaviors of as-fabricated composites, which indicated a boosted crystallization with improved crystallinity with the addition of nanofillers. Furthermore, lignin-g-PDVL-ran-PLLA outperformed lignin-g-PDVL-b-PLLA in terms of the facilitation effect. Mechanical testing showed that PLA/lignin-g-polyester composites possessed better mechanical properties than neat PLA did, which could result from the multiple effects induced by holes and wrinkles that formed between lignin-g-polyester nanofillers and PLA matrix during the stretching process. In contrast to DSC results, the mechanical properties of PLA/lignin-g-PDVL-b-PLLA composites were much better than those of PLA/lignin-g-PDVL-ran-PLLA composites. In addition, the UV-Vis transmission spectroscopy suggested that lignin-g-polyester could endow the composites with an excellent UV-shielding property.
Lignin a commonly used modifier for bio-based PLA materials due to its good biodegradability, structural stability, and the nature of biomacromolecule. However, the poor compatibility between neat lignin and PLA matrix compromises greatly its further application. To this end, lignin-g-polyester with two different molecular structures, i.e. lignin-g-PDVL-ran-PLLA and lignin-g-PDVL-b-PLLA, were specially designed for compatibility improvement and successfully synthesized via ring-opening polymerization with δ-valerolactone (DVL) and L-lactone (L-LA). PDVL as a soft component could reduce the brittleness of PLA with its long polymer chains while L-LA would enhance the compatibility between lignin nanofillers and PLA matrix due to the structural similarity with PLA. Lignin-g-polyester fillers with various segment structures were prepared by tuning the monomer ratio, and a series of PLA/lignin-g-polyester composites with different filler contents were further fabricated via the solution casting method. Structures of lignin-g-polyester were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR), while the uniform dispersion of lignin-g-polyester fillers in PLA composites was verified by field emission scanning electron microscopy (FE-SEM). Differential scanning calorimetry (DSC) was utilized to study the thermal properties and crystallization behaviors of as-fabricated composites, which indicated a boosted crystallization with improved crystallinity with the addition of nanofillers. Furthermore, lignin-g-PDVL-ran-PLLA outperformed lignin-g-PDVL-b-PLLA in terms of the facilitation effect. Mechanical testing showed that PLA/lignin-g-polyester composites possessed better mechanical properties than neat PLA did, which could result from the multiple effects induced by holes and wrinkles that formed between lignin-g-polyester nanofillers and PLA matrix during the stretching process. In contrast to DSC results, the mechanical properties of PLA/lignin-g-PDVL-b-PLLA composites were much better than those of PLA/lignin-g-PDVL-ran-PLLA composites. In addition, the UV-Vis transmission spectroscopy suggested that lignin-g-polyester could endow the composites with an excellent UV-shielding property.
2019, 50(2): 160-169
doi: 10.11777/j.issn1000-3304.2018.18211
Abstract:
pH-Responsive oil-in-water Pickering emulsions using n-decane as oil phase were prepared by mixing quaternized lignin (QAL) and titanium dioxide (TiO2) nanoparticles as emulsifiers. The emulsions stabilized by 0.5 wt% TiO2 neat nanoparticles are extremely unstable due to the strong hydrophilic properties of the nanoparticles. However, when TiO2 nanoparticles are dispersed in neutral solution containing 0.1 wt% QAL, all the emulsifier particles can be applied onto the n-decane/water interface, which greatly improves the stability of the emulsions and the droplet size ranges from 20 μm to 60 μm. Meanwhile, emulsions stabilized by QAL and TiO2 nanoparticles show outstanding pH-responsive properties, which are stable in the range of 6.0 < pH < 7.0 while unstable under the acidic and basic conditions. The synergistic stabilization mechanism of QAL and TiO 2 nanoparticles was studied with zeta potential, adsorption kinetics, and three-phase contact angle. QAL pertains to amphoteric surfactants whose isoelectric point is 7.5. When 6.0 < pH < 7.0, QAL molecules are negatively charged, allowing them to combine with TiO 2 nanoparticles via electrostatic interactions. The hydrophobic phenylpropane skeleton of QAL molecule reduces the hydrophilicity of TiO2 nanoparticles thereby enhances their surface activity to form stable emulsions. However, under the acidic and alkaline conditions, QAL molecules turn into the same charge with TiO2 nanoparticles. Thus, QAL molecules significantly desorb from TiO2 nanoparticles surface due to electrostatic repulsion. TiO2 nanoparticles become intensely hydrophilic again and unable to stay on the oil/water interface, which makes the emulsions unstable as a result. Therefore, the adsorption behaviour between QAL and TiO2 nanoparticles endows Pickering emulsions with double pH-responsive characteristics. With the alternative pH of aqueous phase by adding aqueous HCl and aqueous NaOH, the emulsion system can be recycled many times between emulsification and demulsification while the average droplet size has no obvious change due to its excellent salt tolerance.
pH-Responsive oil-in-water Pickering emulsions using n-decane as oil phase were prepared by mixing quaternized lignin (QAL) and titanium dioxide (TiO2) nanoparticles as emulsifiers. The emulsions stabilized by 0.5 wt% TiO2 neat nanoparticles are extremely unstable due to the strong hydrophilic properties of the nanoparticles. However, when TiO2 nanoparticles are dispersed in neutral solution containing 0.1 wt% QAL, all the emulsifier particles can be applied onto the n-decane/water interface, which greatly improves the stability of the emulsions and the droplet size ranges from 20 μm to 60 μm. Meanwhile, emulsions stabilized by QAL and TiO2 nanoparticles show outstanding pH-responsive properties, which are stable in the range of 6.0 < pH < 7.0 while unstable under the acidic and basic conditions. The synergistic stabilization mechanism of QAL and TiO 2 nanoparticles was studied with zeta potential, adsorption kinetics, and three-phase contact angle. QAL pertains to amphoteric surfactants whose isoelectric point is 7.5. When 6.0 < pH < 7.0, QAL molecules are negatively charged, allowing them to combine with TiO 2 nanoparticles via electrostatic interactions. The hydrophobic phenylpropane skeleton of QAL molecule reduces the hydrophilicity of TiO2 nanoparticles thereby enhances their surface activity to form stable emulsions. However, under the acidic and alkaline conditions, QAL molecules turn into the same charge with TiO2 nanoparticles. Thus, QAL molecules significantly desorb from TiO2 nanoparticles surface due to electrostatic repulsion. TiO2 nanoparticles become intensely hydrophilic again and unable to stay on the oil/water interface, which makes the emulsions unstable as a result. Therefore, the adsorption behaviour between QAL and TiO2 nanoparticles endows Pickering emulsions with double pH-responsive characteristics. With the alternative pH of aqueous phase by adding aqueous HCl and aqueous NaOH, the emulsion system can be recycled many times between emulsification and demulsification while the average droplet size has no obvious change due to its excellent salt tolerance.
2019, 50(2): 170-178
doi: 10.11777/j.issn1000-3304.2018.18178
Abstract:
Metal ion coordinated GO/PMMA composites have been prepared by melt method. The interfacial interaction between the nanofiller and the polymer matrix is significantly increased due to the coordination bonding. As a result, the mechanical and thermal properties of the composites are highly improved. To study the property variation with the change of metal ions and preparation methods, two different metal ions (Cu(II) and Fe(III)) were added into the GO/PMMA system, respectively, and the composites were prepared by two different methods—the direct-melt method and the master-batch method. Fourier transform infrared spectroscopy (FTIR), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), tensile test, and thermogravimetic analysis (TGA) were performed to study the structures and properties of the composites. The FTIR results showed that GO and PMMA are successfully bridged via coordination bonding, for the characteristic peaks showed obvious blue shifts. Raman spectra indicated that coordination causes no extra defect to the GO sheets. SEM images showed that the GO sheets could be homogeneously dispersed in PMMA through master-batch method, while a poor dispersion through direct-melt method. From the tensile test results, it could be seen that the composites prepared by master-batch method had a better mechanical performance than those prepared by direct-melt method because of the different dispersion states. Fe(III)-coordinated composites have better mechanical performance than Cu(II)-coordinated composites do, due to the higher valence state of iron ions. The Young’s modulus and tensile strength of Fe(III)-0.5 wt% GO/PMMA composite are 29.6% and 31.8%, respectively, higher than those of the composite with only GO, and 75.0% and 35.7%, respectively, higher than those of neat PMMA. The temperature of maximum weight loss of Fe(III)-0.5 wt% GO/PMMA is 26 °C higher than that of GO/PMMA, and 82 °C higher than that of neat PMMA. This metal ion coordination method is efficient and simple, and can easily bridge nanofillers and polymer matrixes containing polar groups. This approach opens up a new strategy for improving the performance of many kinds of nanocomposites.
Metal ion coordinated GO/PMMA composites have been prepared by melt method. The interfacial interaction between the nanofiller and the polymer matrix is significantly increased due to the coordination bonding. As a result, the mechanical and thermal properties of the composites are highly improved. To study the property variation with the change of metal ions and preparation methods, two different metal ions (Cu(II) and Fe(III)) were added into the GO/PMMA system, respectively, and the composites were prepared by two different methods—the direct-melt method and the master-batch method. Fourier transform infrared spectroscopy (FTIR), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), tensile test, and thermogravimetic analysis (TGA) were performed to study the structures and properties of the composites. The FTIR results showed that GO and PMMA are successfully bridged via coordination bonding, for the characteristic peaks showed obvious blue shifts. Raman spectra indicated that coordination causes no extra defect to the GO sheets. SEM images showed that the GO sheets could be homogeneously dispersed in PMMA through master-batch method, while a poor dispersion through direct-melt method. From the tensile test results, it could be seen that the composites prepared by master-batch method had a better mechanical performance than those prepared by direct-melt method because of the different dispersion states. Fe(III)-coordinated composites have better mechanical performance than Cu(II)-coordinated composites do, due to the higher valence state of iron ions. The Young’s modulus and tensile strength of Fe(III)-0.5 wt% GO/PMMA composite are 29.6% and 31.8%, respectively, higher than those of the composite with only GO, and 75.0% and 35.7%, respectively, higher than those of neat PMMA. The temperature of maximum weight loss of Fe(III)-0.5 wt% GO/PMMA is 26 °C higher than that of GO/PMMA, and 82 °C higher than that of neat PMMA. This metal ion coordination method is efficient and simple, and can easily bridge nanofillers and polymer matrixes containing polar groups. This approach opens up a new strategy for improving the performance of many kinds of nanocomposites.
2019, 50(2): 179-188
doi: 10.11777/j.issn1000-3304.2018.18183
Abstract:
Using the quantum chemical calculation method and the group contribution method, 12 kinds of quantum chemical structure parameters of 61 polyimide molecular structure model units were collected. In order to simplify the calculation process, a segment of the polymer chain was selected and saturated with methyl group, which was used as the model of the polyimide. Through the path analysis, 5 main factors that affect the dielectric constant of the polyimide films were further screened. On this basis, the multiple linear regression (MLR) and artificial neural network (ANN) methods were constructed. Two quantitative structure-property relationship model (QSPR) were built, and the stability and prediction ability of the models were analyzed. The results revealed the intrinsic relationship between the 5 structural parameters and the dielectric constant, i.e., the fluorine content e−F%, the dipole pitch μ, and the solubility parameter δ of polyimide are positively correlated with the dielectric constant, while the most negative atomic net charge q− and the side length L are negatively correlated with the dielectric constant. MLR-QSPR model has better physical significance and the ANN-QSPR has better accuracy. The accuracy of the models is validated by combining four structures: 6FDA-TriPMPDA, 6FDA-TriPMMDA, 6FDA-TPCF3PDA and 6FDA-TPCF3MDA in our lab. The experimental data show that the average error of the two models is lower than 10% under 1 kHz test condition. Five different fluorine-containing polyimide chain structures were designed according to MLR-QSPR model. The results show that the increase in fluorine content is beneficial to reduce the dielectric constant of the material, but when the fluorine content reaches a certain level, the dielectric constant tends to be stable, which are consistent with the experimental results reported in the literature. When the fluorine content is 34% (k-3), the material possesses the lowest dielectric constant of 2.02. Based on the results of this study, it is believed that QSPR has a good application prospect and theoretical significance in designing new polyimide materials and predicting its properties.
Using the quantum chemical calculation method and the group contribution method, 12 kinds of quantum chemical structure parameters of 61 polyimide molecular structure model units were collected. In order to simplify the calculation process, a segment of the polymer chain was selected and saturated with methyl group, which was used as the model of the polyimide. Through the path analysis, 5 main factors that affect the dielectric constant of the polyimide films were further screened. On this basis, the multiple linear regression (MLR) and artificial neural network (ANN) methods were constructed. Two quantitative structure-property relationship model (QSPR) were built, and the stability and prediction ability of the models were analyzed. The results revealed the intrinsic relationship between the 5 structural parameters and the dielectric constant, i.e., the fluorine content e−F%, the dipole pitch μ, and the solubility parameter δ of polyimide are positively correlated with the dielectric constant, while the most negative atomic net charge q− and the side length L are negatively correlated with the dielectric constant. MLR-QSPR model has better physical significance and the ANN-QSPR has better accuracy. The accuracy of the models is validated by combining four structures: 6FDA-TriPMPDA, 6FDA-TriPMMDA, 6FDA-TPCF3PDA and 6FDA-TPCF3MDA in our lab. The experimental data show that the average error of the two models is lower than 10% under 1 kHz test condition. Five different fluorine-containing polyimide chain structures were designed according to MLR-QSPR model. The results show that the increase in fluorine content is beneficial to reduce the dielectric constant of the material, but when the fluorine content reaches a certain level, the dielectric constant tends to be stable, which are consistent with the experimental results reported in the literature. When the fluorine content is 34% (k-3), the material possesses the lowest dielectric constant of 2.02. Based on the results of this study, it is believed that QSPR has a good application prospect and theoretical significance in designing new polyimide materials and predicting its properties.
2019, 50(2): 189-198
doi: 10.11777/j.issn1000-3304.2018.18198
Abstract:
The properties and thermal treatment effects on the microstructure and stress-strain behaviors of two transparent polyamides, poly(4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAPACM12) and poly(3,3′-dimethyl-4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAMACM12), were studied in this work. Differences in microstructure and the corresponding properties between the two polymers with similar repeating units were found out via comparative analyses. PAPACM12 behaved as a microcrystalline polymer with a distinct glass transition temperature of 135.6 °C and a melting point at 244.6 °C. By contrast, PAMACM12 showed a higher glass transition temperature of 160 °C, as the elimination of thermal history reduced a lot its crystallinity. Besides, cold crystallization was observed for PAPACM12 during the heating process, which gave rise to an exothermic peak on the DSC curve at 174 °C. Comparing the Fourier transform infrared spectroscopy (FTIR) spectra of two polyamides, the band of 961 cm−1 as a crystalline indicator was found present for PAPACM12 but absent for PAMACM12. This observation was consistent with the DSC results obtained above. Further, thermal treatment effects on the aggregate structure and tensile properties were investigated. Experimental results showed that quenching treatment could reduce the yield strength and elongation at break for both samples. Besides, the cold crystallization of PAPACM12 after annealing let two diffraction peaks occur on the integrated pattern of wide-angle X-ray diffraction (WAXD), which corresponded to the d-spacings of 0.50 and 0.45 nm, respectively. These two values approximated to the ones for (100) and (010/110) lattices in the AABB-type polyamides. Moreover, the tensile strength of PAPACM12 increased while the fracture strength decreased after annealing, for cold crystallization process conduced to an improved microcrystalline formation. Differently, both tensile strength and fracture strength of PAMACM12 were decreased by annealing, but its optical transparency was barely affected.
The properties and thermal treatment effects on the microstructure and stress-strain behaviors of two transparent polyamides, poly(4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAPACM12) and poly(3,3′-dimethyl-4,4′-aminocyclohexyl methylene dodecanedicarboxylamide (PAMACM12), were studied in this work. Differences in microstructure and the corresponding properties between the two polymers with similar repeating units were found out via comparative analyses. PAPACM12 behaved as a microcrystalline polymer with a distinct glass transition temperature of 135.6 °C and a melting point at 244.6 °C. By contrast, PAMACM12 showed a higher glass transition temperature of 160 °C, as the elimination of thermal history reduced a lot its crystallinity. Besides, cold crystallization was observed for PAPACM12 during the heating process, which gave rise to an exothermic peak on the DSC curve at 174 °C. Comparing the Fourier transform infrared spectroscopy (FTIR) spectra of two polyamides, the band of 961 cm−1 as a crystalline indicator was found present for PAPACM12 but absent for PAMACM12. This observation was consistent with the DSC results obtained above. Further, thermal treatment effects on the aggregate structure and tensile properties were investigated. Experimental results showed that quenching treatment could reduce the yield strength and elongation at break for both samples. Besides, the cold crystallization of PAPACM12 after annealing let two diffraction peaks occur on the integrated pattern of wide-angle X-ray diffraction (WAXD), which corresponded to the d-spacings of 0.50 and 0.45 nm, respectively. These two values approximated to the ones for (100) and (010/110) lattices in the AABB-type polyamides. Moreover, the tensile strength of PAPACM12 increased while the fracture strength decreased after annealing, for cold crystallization process conduced to an improved microcrystalline formation. Differently, both tensile strength and fracture strength of PAMACM12 were decreased by annealing, but its optical transparency was barely affected.
