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2018 Volume Issue 6
2018, 0(6): 665-667
doi: 10.11777/j.issn1000-3304.2018.18119
Abstract:
Turing structures are beautiful ordered patterns widely found in nature, not only in insects and animals, but also in various plants, and Alan Turing proposed reaction and diffusion mechanism in his paper titled as " The Chemical Basis of Morphogenesis”. How can polymer science be related to Turing structures? Recently Professor Zhang in Zhejiang University published a paper in Science clearly reporting the preparation of polyamide nanofiltration membrane with Turing structures. By introducing hydrophilic polyvinyl alcohol into the aqueous phase to reduce the diffusion rate of piperazine via hydrogen bonding and increase solution viscosity, the Turing’s reaction-diffusion condition can be realized, and manipulation of shapes by control of reaction conditions enabled the creation of membranes with bubble or tube structures. These membranes exhibit excellent water-salt separation performance that surpasses the upper-bound line of traditional desalination membranes. This highlight recommends the breakthrough in polyamide membrane with excellent desalination performance by Chinese scientists, and the profound influence on preparation of more advanced polymer materials via " reaction-diffusion system” is expected.
Turing structures are beautiful ordered patterns widely found in nature, not only in insects and animals, but also in various plants, and Alan Turing proposed reaction and diffusion mechanism in his paper titled as " The Chemical Basis of Morphogenesis”. How can polymer science be related to Turing structures? Recently Professor Zhang in Zhejiang University published a paper in Science clearly reporting the preparation of polyamide nanofiltration membrane with Turing structures. By introducing hydrophilic polyvinyl alcohol into the aqueous phase to reduce the diffusion rate of piperazine via hydrogen bonding and increase solution viscosity, the Turing’s reaction-diffusion condition can be realized, and manipulation of shapes by control of reaction conditions enabled the creation of membranes with bubble or tube structures. These membranes exhibit excellent water-salt separation performance that surpasses the upper-bound line of traditional desalination membranes. This highlight recommends the breakthrough in polyamide membrane with excellent desalination performance by Chinese scientists, and the profound influence on preparation of more advanced polymer materials via " reaction-diffusion system” is expected.
2018, 0(6): 668-673
doi: 10.11777/j.issn1000-3304.2018.18074
Abstract:
Hybrid copolymerization is the process where two or more unlike monomers with different polymerizable groups polymerize together. It is revolutionary to the conventional copolymerization where the monomers have the same polymerizable groups. Hybrid copolymerization provides new routes for synthesis of polymers and gives great possibility to produce polymers with novel properties. However, because the unlike monomers follow different polymerization mechanisms and their reactivities are quite different, hybrid copolymerization has long been a challenge. Fortunately, some breakthroughs have been made in vinyl addition and ring-opening hybrid copolymerization since 1980’s. Bailey et al. first reported the radical ring-opening hybrid copolymerization of 2-methylene-1,3-dioxepane (MDO) with vinyl monomers such as styrene (St) and methyl methacrylate (MMA) in 1982. Such a copolymerization can yield relatively high molecular weight polymers (104 − 10 5), but the cyclic monomers are only limited to cyclic ketene acetals. Zwitteronic hybrid copolymerization was reported later but it only produces oligomers. With the development of organocatalysis, anionic and cationic hybrid copolymerizations were studied in recent years. Cationic hybrid copolymerization or the so-called concurrent cationic copolymerization of isobutylene oxide and vinyl ether was reported in 2013. The copolymerization is also applicable to other cyclic monomers with epoxides, but it produces polymers with a relatively low molecular weight (103 − 10 4). In 2012, anionic hybrid copolymerization of ε-caprolactone (CL) and methyl methacrylate (MMA) was reported by our laboratory for the first time. Such a copolymerization is applicable to many common monomers including cyclic ester or cyclic ether and vinyl esters. The polymer synthesized by anionic hybrid copolymerization has a high molecular weight (104 − 10 5) so that it can be used in different materials. Actually, clickable or hybranched biodegradable polymers were already prepared via the copolymerization. Particularly, it was used to develop high performance biodegradable polymers for marine anti-biofouling. The work describes the progress in hybrid copolymerization.
Hybrid copolymerization is the process where two or more unlike monomers with different polymerizable groups polymerize together. It is revolutionary to the conventional copolymerization where the monomers have the same polymerizable groups. Hybrid copolymerization provides new routes for synthesis of polymers and gives great possibility to produce polymers with novel properties. However, because the unlike monomers follow different polymerization mechanisms and their reactivities are quite different, hybrid copolymerization has long been a challenge. Fortunately, some breakthroughs have been made in vinyl addition and ring-opening hybrid copolymerization since 1980’s. Bailey et al. first reported the radical ring-opening hybrid copolymerization of 2-methylene-1,3-dioxepane (MDO) with vinyl monomers such as styrene (St) and methyl methacrylate (MMA) in 1982. Such a copolymerization can yield relatively high molecular weight polymers (104 − 10 5), but the cyclic monomers are only limited to cyclic ketene acetals. Zwitteronic hybrid copolymerization was reported later but it only produces oligomers. With the development of organocatalysis, anionic and cationic hybrid copolymerizations were studied in recent years. Cationic hybrid copolymerization or the so-called concurrent cationic copolymerization of isobutylene oxide and vinyl ether was reported in 2013. The copolymerization is also applicable to other cyclic monomers with epoxides, but it produces polymers with a relatively low molecular weight (103 − 10 4). In 2012, anionic hybrid copolymerization of ε-caprolactone (CL) and methyl methacrylate (MMA) was reported by our laboratory for the first time. Such a copolymerization is applicable to many common monomers including cyclic ester or cyclic ether and vinyl esters. The polymer synthesized by anionic hybrid copolymerization has a high molecular weight (104 − 10 5) so that it can be used in different materials. Actually, clickable or hybranched biodegradable polymers were already prepared via the copolymerization. Particularly, it was used to develop high performance biodegradable polymers for marine anti-biofouling. The work describes the progress in hybrid copolymerization.
2018, 0(6): 674-681
doi: 10.11777/j.issn1000-3304.2017.17262
Abstract:
A series of water-soluble double-responsive core cross-linked star polymers (PNSB@PAA-DMP), in which poly(3-acrylamidophenylboronic acid-co-acrylamide) (PAA-DMP) served as the pH-responsive arm and poly(N-isopropyl acrylamide-co-styrene-co-N,N′-methylenebisacrylamide) (PNSB) as the thermoresponsive core, have been successively prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization using the " arm-first” approach. Poly(AAPBA-co-AM) is first prepared via RAFT polymerization to give a well-defined linear hydrophilic macro-RAFT agent, which subsequently copolymerizes with thermosensitive monomer NIPAM (N-isopropyl acrylamide), crosslinker Bis (N,N′-methylenebisacrylamide) and St (styrene) to give the desired pH and thermoresponsive star polymers (PNSB@PAA-DMP). Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H-NMR) are empolyed to characterize the structure and composition of the resultant polymers. The molecular weight of the polymers are obtained by gel permeation chromatography (GPC). The morphology and particle size of polymer under dry conditions are characterized by transmission electron microscopy (TEM). In addition, the phase transition behavior of the polymers in aqueous solutions at low concentration is investigate by dynamic light scattering (DLS) and ultraviolet-visible spectroscopy (UV-Vis). The results show that the obtained PNSB@PAA-DMP polymers exhibit reversible thermal-induced volume phase transition and pH responsibility. The lower critical solution temperature (LCST) of the core cross-linked star polymers in aqueous solutions can be tuned by changing the feeding ratio of the hydrophobic monomer St. In addition, the LCST of the polymer solution could also be affected by changing the pH of the polymer solution. What is most interesting is that sol-gel transition of the polymer solution can be achieved by controlling temperature and pH at a higher concentration. For example, a free flowing solution (20 mg/mL, pH = 9) is observed at 15 °C, but a white hydrogel is formed when this solution is heated to 30 °C. When pH = 12, the polymer solution (20 mg/mL), at any temperature, is always in the sol state, which quickly settles at the vial bottom when the sample vials is inverted.
A series of water-soluble double-responsive core cross-linked star polymers (PNSB@PAA-DMP), in which poly(3-acrylamidophenylboronic acid-co-acrylamide) (PAA-DMP) served as the pH-responsive arm and poly(N-isopropyl acrylamide-co-styrene-co-N,N′-methylenebisacrylamide) (PNSB) as the thermoresponsive core, have been successively prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization using the " arm-first” approach. Poly(AAPBA-co-AM) is first prepared via RAFT polymerization to give a well-defined linear hydrophilic macro-RAFT agent, which subsequently copolymerizes with thermosensitive monomer NIPAM (N-isopropyl acrylamide), crosslinker Bis (N,N′-methylenebisacrylamide) and St (styrene) to give the desired pH and thermoresponsive star polymers (PNSB@PAA-DMP). Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H-NMR) are empolyed to characterize the structure and composition of the resultant polymers. The molecular weight of the polymers are obtained by gel permeation chromatography (GPC). The morphology and particle size of polymer under dry conditions are characterized by transmission electron microscopy (TEM). In addition, the phase transition behavior of the polymers in aqueous solutions at low concentration is investigate by dynamic light scattering (DLS) and ultraviolet-visible spectroscopy (UV-Vis). The results show that the obtained PNSB@PAA-DMP polymers exhibit reversible thermal-induced volume phase transition and pH responsibility. The lower critical solution temperature (LCST) of the core cross-linked star polymers in aqueous solutions can be tuned by changing the feeding ratio of the hydrophobic monomer St. In addition, the LCST of the polymer solution could also be affected by changing the pH of the polymer solution. What is most interesting is that sol-gel transition of the polymer solution can be achieved by controlling temperature and pH at a higher concentration. For example, a free flowing solution (20 mg/mL, pH = 9) is observed at 15 °C, but a white hydrogel is formed when this solution is heated to 30 °C. When pH = 12, the polymer solution (20 mg/mL), at any temperature, is always in the sol state, which quickly settles at the vial bottom when the sample vials is inverted.
2018, 0(6): 682-691
doi: 10.11777/j.issn1000-3304.2017.17335
Abstract:
Though chemotherapeutics has been one of the most widely used treatments for tumor therapy, it is still heavily limited due to its poor pharmacokinetics, undesirable intracellular uptake and inevitable side effects. In order to overcome these barriers, various functional groups have been introduced in drug delivery system to enhance the therapeutic efficiency of chemotherapy. In this study, a novel drug delivery system for tumor nuclear accurate targeting was designed in order to achieve precise tumor nuclear treatment. The chemotherapeutic drug (doxorubicin, DOX) was encapsulated in amphiphilic dendritic peptide with nuclear localization function to form a regular nanoparticle DD. After that, electronegative hyaluronic acid (HA) with ability of tumor targeting was coated on the surface of nanoparticle DD via electrostatic interaction to form tumor nuclear targeting drug delivery system HDD. The presence of HA endowed HDD with the tumor targeting ability and charge shielding effect, which could increase the stability of nanodrug, promote the specific internalization by tumor cells and reduce the non-specific uptake by normal tissue/cells. Furthermore, it was found that the drug delivery system HDD could realize the facile internalization by tumor cells via CD44 receptor-mediated recognition. After the degradation of HA shell by hyaluronidase (HAase) in endosome, the nuclear targeted nanodrug DD was exposed, and DOX was carried to the region of nuclear accurately by inheriting the ability from nuclear-targeted peptide. The precise targeting of drug to nuclei could be beneficial to the improvement of drug utilization as well as the suppression of tumor cells. The characteristics of this tumor nuclear accurate targeting drug delivery system, including particle sizes, zeta potential, drug loading capacity, drug release behavior, cellular uptake and antitumor efficacy, were evaluated. All of the studies confirmed that the precise tumor nuclear targeting drug delivery system HDD displayed prominent antitumor efficacy with insignificant adverse effects to normal cells in vitro, which indicated that the precise tumor nuclear targeting delivery system supplies a useful strategy for tumor therapy.
Though chemotherapeutics has been one of the most widely used treatments for tumor therapy, it is still heavily limited due to its poor pharmacokinetics, undesirable intracellular uptake and inevitable side effects. In order to overcome these barriers, various functional groups have been introduced in drug delivery system to enhance the therapeutic efficiency of chemotherapy. In this study, a novel drug delivery system for tumor nuclear accurate targeting was designed in order to achieve precise tumor nuclear treatment. The chemotherapeutic drug (doxorubicin, DOX) was encapsulated in amphiphilic dendritic peptide with nuclear localization function to form a regular nanoparticle DD. After that, electronegative hyaluronic acid (HA) with ability of tumor targeting was coated on the surface of nanoparticle DD via electrostatic interaction to form tumor nuclear targeting drug delivery system HDD. The presence of HA endowed HDD with the tumor targeting ability and charge shielding effect, which could increase the stability of nanodrug, promote the specific internalization by tumor cells and reduce the non-specific uptake by normal tissue/cells. Furthermore, it was found that the drug delivery system HDD could realize the facile internalization by tumor cells via CD44 receptor-mediated recognition. After the degradation of HA shell by hyaluronidase (HAase) in endosome, the nuclear targeted nanodrug DD was exposed, and DOX was carried to the region of nuclear accurately by inheriting the ability from nuclear-targeted peptide. The precise targeting of drug to nuclei could be beneficial to the improvement of drug utilization as well as the suppression of tumor cells. The characteristics of this tumor nuclear accurate targeting drug delivery system, including particle sizes, zeta potential, drug loading capacity, drug release behavior, cellular uptake and antitumor efficacy, were evaluated. All of the studies confirmed that the precise tumor nuclear targeting drug delivery system HDD displayed prominent antitumor efficacy with insignificant adverse effects to normal cells in vitro, which indicated that the precise tumor nuclear targeting delivery system supplies a useful strategy for tumor therapy.
2018, 0(6): 692-699
doi: 10.11777/j.issn1000-3304.2017.17265
Abstract:
Through molecular design, three different block copolymers PPENK-b-PEEKK with phthalazinone moiety were synthesized via modest polycondensation reaction from the two macromers PEEKK-OH and PPENK-F. Hydroxy terminated PEEKK-OH macromer was obtained by solution polymerization from HQ and BFBB with sulfolane as the solvent. And the molecular weight of PEEKK-OH was successfully controlled by adjusting the monomer ratio, and the polymerized conditions were optimized by orthogonal experiments. While different molecular weight PPENK-F macromer, endcapped with ―F groups, was prepared from DHPZ, DFK and DFBN. Chemical structures and properties of these block copolymers were inverstigated by Fourier transforming infrared spectrum (FTIR), wide X-ray diffraction (WXRD), differantial scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The FTIR spectra confirmed the formation of the block copolymers. Furthermore, WXRD measurement showed that all the block copolymers presented crystalline structure, and the crystallinity of the coplolymers decreased with increasing molecular weight of PPENK-F chain segments. All the block copolymers showed only one glass transition temperature (Tg), above that of PEEKK-OH. The Tg of the block copolymers increased with the molecular weight of PPENK-F, due to the introduction of PPENK chain segments into the block copolymers. Moreover, for the reason of of PEEKK incorporation, all these copolymers have a same melting point (Tm) of about 340 °C, which would facilitate their thermal processing. Besides, all the three copolymers also exhibited remarkable thermal stability in nitrogen atmosphere with the Td5% weight loss temperature ranging from 491 °C to 510 °C, and Td10% from 523 °C to 530 °C, respectively. The char yields of the three copolymers at 800 °C were higher than 63%. Finally, all the copolymers showed improved solubility in selectively tested organic solvents, such as NMP and sulfolane, due to the introduction of twisted and non-coplanar DHPZ structure. Consequently, theses materials are potential candidates for the aerospace applications.
Through molecular design, three different block copolymers PPENK-b-PEEKK with phthalazinone moiety were synthesized via modest polycondensation reaction from the two macromers PEEKK-OH and PPENK-F. Hydroxy terminated PEEKK-OH macromer was obtained by solution polymerization from HQ and BFBB with sulfolane as the solvent. And the molecular weight of PEEKK-OH was successfully controlled by adjusting the monomer ratio, and the polymerized conditions were optimized by orthogonal experiments. While different molecular weight PPENK-F macromer, endcapped with ―F groups, was prepared from DHPZ, DFK and DFBN. Chemical structures and properties of these block copolymers were inverstigated by Fourier transforming infrared spectrum (FTIR), wide X-ray diffraction (WXRD), differantial scanning calorimetry (DSC) and thermogravimetric analyses (TGA). The FTIR spectra confirmed the formation of the block copolymers. Furthermore, WXRD measurement showed that all the block copolymers presented crystalline structure, and the crystallinity of the coplolymers decreased with increasing molecular weight of PPENK-F chain segments. All the block copolymers showed only one glass transition temperature (Tg), above that of PEEKK-OH. The Tg of the block copolymers increased with the molecular weight of PPENK-F, due to the introduction of PPENK chain segments into the block copolymers. Moreover, for the reason of of PEEKK incorporation, all these copolymers have a same melting point (Tm) of about 340 °C, which would facilitate their thermal processing. Besides, all the three copolymers also exhibited remarkable thermal stability in nitrogen atmosphere with the Td5% weight loss temperature ranging from 491 °C to 510 °C, and Td10% from 523 °C to 530 °C, respectively. The char yields of the three copolymers at 800 °C were higher than 63%. Finally, all the copolymers showed improved solubility in selectively tested organic solvents, such as NMP and sulfolane, due to the introduction of twisted and non-coplanar DHPZ structure. Consequently, theses materials are potential candidates for the aerospace applications.
2018, 0(6): 700-711
doi: 10.11777/j.issn1000-3304.2017.17290
Abstract:
A novel nanocomposite material of chitosan-g-polytetrahydrofuran (PTHF) graft copolymers with silver (Ag) nanoparticles, CS-g-PTHF/Ag, was successfully in situ prepared via combination of living cationic opening polymerization of tetrahydrofuran (THF) with controlled termination of living PTHF chains " grafting onto” chitosan macromolecular backbone. Chemical structure of CS-g-PTHF/Ag was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), and X-ray photoelectron spectroscopy (XPS). The total content of Ag, drug releasing rate and micromorphology of CS-g-PTHF/Ag composites were characterized by ultraviolet spectroscopy (UV), polarizing microscopy (POM), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM), respectively. The results show that the acylation degree of average functional groups in single glucosamine was 20%. The number-average molecular weight (Mn) and average grafting number could be designed by changing the dosage of allylBr/AgClO4 initiating system and the molar ratio of living PTHF chains to the ―NH2 functional groups in chitosan backbone. The Mn,PTHF ranged from 1400 to 2600 and average grafting number increased from 4 to 21 on the basis of every 1000 glucosamine units along the macromolecular backbone. The PTHF branches influenced the crystallinity of the acylated chitosan backbone. The microphase separation of CS-g-PTHF/Ag nanocomposite was observed, and the micromorphology was related to grafting density in the CS-g-PTHF graft copolymers. The crystallization activity of the backbone was limited with an increase in the grafting number of PTHF branches. Meanwhile, the CS-g-PTHF graft copolymer was found to behave pH-sensitive drug delivery. The size of the drug-loaded microspheres decreased with the increasing average grafting number in CS-g-PTHF graft copolymers. Drug-loading percentage of different CS-g-PTHF drug deliveries varied from 53% to 80%. Taking CS-g6-PTHF1.4k as an example, its drug-releasing rate (DRR) was accelerated in weak acid of phosphate buffered solution (pH = 6.0). The drug-releasing process included three stages: in the first stage (4 h), CS-g6-PTHF1.4k drug delivery released fast with a DRR of 63%. In the second stage from 4 h to 8 h, DRR was slightly changed. In the third stage, drug delivery accelerated and DRR reached 100%. Drug was inhibited to release in the simulated intestinal fluid (pH = 1.2), simulated gastrointestinal fluid (pH = 7.4), simulated blood (pH = 7.4). In simulated intestinal fluid (pH = 1.2), drug release was fast in the first 4 h, and the accumulated drug release was 29%, and accumulated DRR was 35% within 25 h. In simulated gastrointestinal fluid (pH = 7.4) and simulated blood (pH = 7.4), the drug-release rate reached a maximum in the first 2 h, and DDR was 51% in 25 h. The total mass content of Ag in CS-g-PTHF/Ag nanocomposite varied from 2.2% to 5.7%, which led to antibacterial performance in CS-g-PTHF/Ag nanocomposite. For CS-g7-PTHF2.6k/Ag-5.7, diameter of inhibition zone of Escherichhia coli was 13.0 mm, and of Aspergillus niger was 10.5 mm. This novel CS-g-PTHF/Ag nanocomposite, with the biocompatibility of rigid chitosan, the humidity resistance of soft polytetrahydrofuran, and the antibacterial activity of nano-silver all combined, would have a prospect in biomedical application.
A novel nanocomposite material of chitosan-g-polytetrahydrofuran (PTHF) graft copolymers with silver (Ag) nanoparticles, CS-g-PTHF/Ag, was successfully in situ prepared via combination of living cationic opening polymerization of tetrahydrofuran (THF) with controlled termination of living PTHF chains " grafting onto” chitosan macromolecular backbone. Chemical structure of CS-g-PTHF/Ag was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H-NMR), and X-ray photoelectron spectroscopy (XPS). The total content of Ag, drug releasing rate and micromorphology of CS-g-PTHF/Ag composites were characterized by ultraviolet spectroscopy (UV), polarizing microscopy (POM), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM), respectively. The results show that the acylation degree of average functional groups in single glucosamine was 20%. The number-average molecular weight (Mn) and average grafting number could be designed by changing the dosage of allylBr/AgClO4 initiating system and the molar ratio of living PTHF chains to the ―NH2 functional groups in chitosan backbone. The Mn,PTHF ranged from 1400 to 2600 and average grafting number increased from 4 to 21 on the basis of every 1000 glucosamine units along the macromolecular backbone. The PTHF branches influenced the crystallinity of the acylated chitosan backbone. The microphase separation of CS-g-PTHF/Ag nanocomposite was observed, and the micromorphology was related to grafting density in the CS-g-PTHF graft copolymers. The crystallization activity of the backbone was limited with an increase in the grafting number of PTHF branches. Meanwhile, the CS-g-PTHF graft copolymer was found to behave pH-sensitive drug delivery. The size of the drug-loaded microspheres decreased with the increasing average grafting number in CS-g-PTHF graft copolymers. Drug-loading percentage of different CS-g-PTHF drug deliveries varied from 53% to 80%. Taking CS-g6-PTHF1.4k as an example, its drug-releasing rate (DRR) was accelerated in weak acid of phosphate buffered solution (pH = 6.0). The drug-releasing process included three stages: in the first stage (4 h), CS-g6-PTHF1.4k drug delivery released fast with a DRR of 63%. In the second stage from 4 h to 8 h, DRR was slightly changed. In the third stage, drug delivery accelerated and DRR reached 100%. Drug was inhibited to release in the simulated intestinal fluid (pH = 1.2), simulated gastrointestinal fluid (pH = 7.4), simulated blood (pH = 7.4). In simulated intestinal fluid (pH = 1.2), drug release was fast in the first 4 h, and the accumulated drug release was 29%, and accumulated DRR was 35% within 25 h. In simulated gastrointestinal fluid (pH = 7.4) and simulated blood (pH = 7.4), the drug-release rate reached a maximum in the first 2 h, and DDR was 51% in 25 h. The total mass content of Ag in CS-g-PTHF/Ag nanocomposite varied from 2.2% to 5.7%, which led to antibacterial performance in CS-g-PTHF/Ag nanocomposite. For CS-g7-PTHF2.6k/Ag-5.7, diameter of inhibition zone of Escherichhia coli was 13.0 mm, and of Aspergillus niger was 10.5 mm. This novel CS-g-PTHF/Ag nanocomposite, with the biocompatibility of rigid chitosan, the humidity resistance of soft polytetrahydrofuran, and the antibacterial activity of nano-silver all combined, would have a prospect in biomedical application.
2018, 0(6): 712-720
doi: 10.11777/j.issn1000-3304.2017.17245
Abstract:
Naphthalene diimides (NDIs) as excellent organic semiconductors are difficult to be synthesized, because it is difficult to separate the key intermediate 2,6-dibromo-NDI from 2-bromo-NDI. A highly efficient synthesis of 2,6-dibromo-NDI was developed in this work. Perfluoroalkylated NDIs are excellent electron transport materials, while they are unsuitable for solution process because of their poor solubility. Since semi-perfluoroalkylated conjugated compounds have much better solubility than their perfluoroalkylated counterparts, different semi-perfluoroalkyl groups were introduced to the N-terminals of NDIs, and six conjugated polymers with donor-acceptor structure were synthesized by multi-step reactions. The chemical structure, optical properties, electrochemical properties, thermal stability, contact angle, and self-assembly properties of the target polymers were studied. The results demonstrate that suitable semi-pefluoroalkyl groups are critical to the synthesis of the soluble polymers. All these polymers are readily soluble in organic solvents. Solid absorption of these polymers red-shifts compared to their solution absorption, indicating aggregation in solid state. The absorption red-shifts obviously by increasing electron donating ability of the donor unit. The optical bandgaps of the semi-perfluoroalkylated polymers are 0.3 eV lower than those of the regular polymers. The LUMO energy levels of these polymers are as low as −3.84 ~ −3.90 eV, indicating their strong electron accepting ability. The LUMO energy levels of the semi-perfluoroalkylated polymers are about 0.1 eV lower than those of NDI polymers with regular alkyl groups, which is attributed to the strong electron-withdrawing properties of their fluorine atoms. With simple spin-coating and evaporation, the polymer P5 can be self-assembled into ordered fibers with 500 nm in length and 30 nm in width, which is in favor of charge transfer. All these polymers have good thermal stability with their decomposing temperature above 375 °C. Their higher fluorine ratio and higher contact angles are the reflection of their water repellent properties. The mobility of these polymers is measured with space charge-limiting current (SCLC) method using the device structure of ITO/ZnO/polymer/Al, and all these polymers prove to be electron transporting materials.
Naphthalene diimides (NDIs) as excellent organic semiconductors are difficult to be synthesized, because it is difficult to separate the key intermediate 2,6-dibromo-NDI from 2-bromo-NDI. A highly efficient synthesis of 2,6-dibromo-NDI was developed in this work. Perfluoroalkylated NDIs are excellent electron transport materials, while they are unsuitable for solution process because of their poor solubility. Since semi-perfluoroalkylated conjugated compounds have much better solubility than their perfluoroalkylated counterparts, different semi-perfluoroalkyl groups were introduced to the N-terminals of NDIs, and six conjugated polymers with donor-acceptor structure were synthesized by multi-step reactions. The chemical structure, optical properties, electrochemical properties, thermal stability, contact angle, and self-assembly properties of the target polymers were studied. The results demonstrate that suitable semi-pefluoroalkyl groups are critical to the synthesis of the soluble polymers. All these polymers are readily soluble in organic solvents. Solid absorption of these polymers red-shifts compared to their solution absorption, indicating aggregation in solid state. The absorption red-shifts obviously by increasing electron donating ability of the donor unit. The optical bandgaps of the semi-perfluoroalkylated polymers are 0.3 eV lower than those of the regular polymers. The LUMO energy levels of these polymers are as low as −3.84 ~ −3.90 eV, indicating their strong electron accepting ability. The LUMO energy levels of the semi-perfluoroalkylated polymers are about 0.1 eV lower than those of NDI polymers with regular alkyl groups, which is attributed to the strong electron-withdrawing properties of their fluorine atoms. With simple spin-coating and evaporation, the polymer P5 can be self-assembled into ordered fibers with 500 nm in length and 30 nm in width, which is in favor of charge transfer. All these polymers have good thermal stability with their decomposing temperature above 375 °C. Their higher fluorine ratio and higher contact angles are the reflection of their water repellent properties. The mobility of these polymers is measured with space charge-limiting current (SCLC) method using the device structure of ITO/ZnO/polymer/Al, and all these polymers prove to be electron transporting materials.
2018, 0(6): 721-732
doi: 10.11777/j.issn1000-3304.2017.17203
Abstract:
Graphene oxide (GO) is used to improve mechanical, thermal and functional properties of epoxy, in which the challenges are to achieve strong interfacial bonding between GO and epoxy resins with a uniform dispersion of GO within epoxy resins. GO can be partially reduced and exfoliated through modification by dopamine (DA), which can improve the dispersion of DGO in epoxy resins and achieve better interfacial bonding between DGO and the epoxy resins. The purpose of this work is to investigate the effects of GO modification by DA (DGO) on the mechanical and thermal properties of a multifunctional epoxy —diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). First, GO and DA were mixed with deionized water and then reacted to prepare DGO. The obtained DGO without desiccation and the pristine GO are respectively dispersed in acetone with TDE-85, and TDE-85/DGO and TDE-85/GO mixture are therefore prepared by sonication and used as master batches. The master batches are then diluted by adding a certain amount of TDE-85 and cured at elevated temperature to obtain the composites of TDE-85/DGO and TDE-85/GO with varied contents of DGO and GO. Finally, the results of the modification are demonstrated, and the properties of the composites are characterized. It is found that, GO is partially reduced and exfoliated by DA modification, and the mechanical properties of TDE-85 is enhanced upon adding DGO without losing its heat resistance. Especially when the content of DGO is 0.05 wt%, the critical stress intensity factor (KIc), tensile strength, elongation at break, and glass-transition temperature (Tg) of TDE-85/DGO composites are improved by 284.2%, 17.59%, 13.84% and 4.0%, respectively. The strong interfacial bonding between TDE-85 and DGO owing to the functional groups of PDA on the surface of DGO, the obvious crack deflection and crack pinning exhibited at the location of the DGO observed in SEM may be responsible for the improved mechanical properties. Furthermore, the tensile strength, KIc and Tg of TDE-85/DGO system are compared with those of similar toughened materials by other methods, and the result suggests that the present process is an effective toughened method. Thus, this work provides a toughened epoxy for preparing fiber reinforced composites with high-strength and high-modulus.
Graphene oxide (GO) is used to improve mechanical, thermal and functional properties of epoxy, in which the challenges are to achieve strong interfacial bonding between GO and epoxy resins with a uniform dispersion of GO within epoxy resins. GO can be partially reduced and exfoliated through modification by dopamine (DA), which can improve the dispersion of DGO in epoxy resins and achieve better interfacial bonding between DGO and the epoxy resins. The purpose of this work is to investigate the effects of GO modification by DA (DGO) on the mechanical and thermal properties of a multifunctional epoxy —diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). First, GO and DA were mixed with deionized water and then reacted to prepare DGO. The obtained DGO without desiccation and the pristine GO are respectively dispersed in acetone with TDE-85, and TDE-85/DGO and TDE-85/GO mixture are therefore prepared by sonication and used as master batches. The master batches are then diluted by adding a certain amount of TDE-85 and cured at elevated temperature to obtain the composites of TDE-85/DGO and TDE-85/GO with varied contents of DGO and GO. Finally, the results of the modification are demonstrated, and the properties of the composites are characterized. It is found that, GO is partially reduced and exfoliated by DA modification, and the mechanical properties of TDE-85 is enhanced upon adding DGO without losing its heat resistance. Especially when the content of DGO is 0.05 wt%, the critical stress intensity factor (KIc), tensile strength, elongation at break, and glass-transition temperature (Tg) of TDE-85/DGO composites are improved by 284.2%, 17.59%, 13.84% and 4.0%, respectively. The strong interfacial bonding between TDE-85 and DGO owing to the functional groups of PDA on the surface of DGO, the obvious crack deflection and crack pinning exhibited at the location of the DGO observed in SEM may be responsible for the improved mechanical properties. Furthermore, the tensile strength, KIc and Tg of TDE-85/DGO system are compared with those of similar toughened materials by other methods, and the result suggests that the present process is an effective toughened method. Thus, this work provides a toughened epoxy for preparing fiber reinforced composites with high-strength and high-modulus.
2018, 0(6): 733-740
doi: 10.11777/j.issn1000-3304.2017.17331
Abstract:
Colloidal photonic crystal is a type of novel artificial functional material, which can effectively control the propagation of light wave with high reflection by its photonic band gap. It has the advantages of low-cost, simple process of preparation and the potential of fabricating in large scale. When the band gap located in the infrared band, colloidal photonic crystal could effectively manage the heat radiation, and reduce the detectability in the infrared band. Thus, there is a great potential in the field of infrared stealth technology for the photonic crystal. An infrared material of colloidal photonic crystal with a low cost and easy preparation process is reported in this study. Micrometer monodisperse polystyrene (PS) colloidal microspheres with different particle sizes were obtained by formulation control. The effect of the formulation on the size of PS microspheres was also studied, and theoretical principles of influencing factors were stated. The structured two-dimensional photonic crystal materials were prepared by gas-liquid interface self-assembly method. The bright Debye ring was observed clearly by laser vertical irradiation. PS colloidal microspheres were self-assembled into high-quality opal and three-dimensional photonic crystal using an improved vertical self-assembled deposition method by adjusting the temperature and concentration of the microsphere in their aqueous solution. The controllable preparation and the characteristics of infrared band optical were studied using laser particle size analyzer, scanning electron microscope, infrared spectrometer etc. The forbidden band gap of the three-dimensional photonic crystals assembled from monodisperse colloidal microspheres of 1.10 μm was 2.25 μm, and that of the three-dimensional photonic crystals assembled from PS monodisperse colloidal microspheres of 1.20 μm was 2.47 μm. The above results were consistent with the theoretical calculation. The photonic crystal material could change the infrared radiation characteristics of the corresponding band gap and is expected to be applied to photonic crystal templates, thermal barrier coating materials and infrared stealth technology fields.
Colloidal photonic crystal is a type of novel artificial functional material, which can effectively control the propagation of light wave with high reflection by its photonic band gap. It has the advantages of low-cost, simple process of preparation and the potential of fabricating in large scale. When the band gap located in the infrared band, colloidal photonic crystal could effectively manage the heat radiation, and reduce the detectability in the infrared band. Thus, there is a great potential in the field of infrared stealth technology for the photonic crystal. An infrared material of colloidal photonic crystal with a low cost and easy preparation process is reported in this study. Micrometer monodisperse polystyrene (PS) colloidal microspheres with different particle sizes were obtained by formulation control. The effect of the formulation on the size of PS microspheres was also studied, and theoretical principles of influencing factors were stated. The structured two-dimensional photonic crystal materials were prepared by gas-liquid interface self-assembly method. The bright Debye ring was observed clearly by laser vertical irradiation. PS colloidal microspheres were self-assembled into high-quality opal and three-dimensional photonic crystal using an improved vertical self-assembled deposition method by adjusting the temperature and concentration of the microsphere in their aqueous solution. The controllable preparation and the characteristics of infrared band optical were studied using laser particle size analyzer, scanning electron microscope, infrared spectrometer etc. The forbidden band gap of the three-dimensional photonic crystals assembled from monodisperse colloidal microspheres of 1.10 μm was 2.25 μm, and that of the three-dimensional photonic crystals assembled from PS monodisperse colloidal microspheres of 1.20 μm was 2.47 μm. The above results were consistent with the theoretical calculation. The photonic crystal material could change the infrared radiation characteristics of the corresponding band gap and is expected to be applied to photonic crystal templates, thermal barrier coating materials and infrared stealth technology fields.
2018, (6): 741-747
doi: 10.11777/j.issn1000-3304.2017.17315
Abstract:
Dewetting behaviors on PDMS substrate of linear polystyrene (LPS) film, ring polystyrene (RPS) film and the blended films with different mixing ratios are investigated. The radii of the holes exhibit exponential growth with time for the above mentioned types of films. The dewetting velocity of RPS film appears slower than that of LPS film, and the velocity of the blended films falls in between the above two. Moreover, the velocity of the blended films decreases with increasing RPS fraction. The surface energies of the films are calculated from the contact angles of two different liquids (water and ethylene glycol) on top of the corresponding films. Results show that the surface energies of the blended films are smaller than those of LPS film and RPS film. The surface energy reaches the lowest value for the blended film with 70% of RPS, which may be caused by the different roughness measurements for LPS film, RPS film and the blended films. The viscosities of these films are obtained through the radii of the dewetting holes, the dewetting velocities, the widths of the rims and the receding contact angles along dewetting process. Results show LPS film has a lower viscosity than RPS film. The viscosities of the blended films fall in between those of LPS film and RPS film, and increase with increasing RPS concentration. Moreover, the experimental viscosities of the blended films present lower values than those calculated from the pure-component viscosity using a binary mixing rule. The ratio of the experimental viscosity to the calculated viscosity reaches a lowest value with 70% of RPS. This may be attributed to the efficient packing ability of the ring chains, the effect of chain threading and the amount of free volume in the film.
Dewetting behaviors on PDMS substrate of linear polystyrene (LPS) film, ring polystyrene (RPS) film and the blended films with different mixing ratios are investigated. The radii of the holes exhibit exponential growth with time for the above mentioned types of films. The dewetting velocity of RPS film appears slower than that of LPS film, and the velocity of the blended films falls in between the above two. Moreover, the velocity of the blended films decreases with increasing RPS fraction. The surface energies of the films are calculated from the contact angles of two different liquids (water and ethylene glycol) on top of the corresponding films. Results show that the surface energies of the blended films are smaller than those of LPS film and RPS film. The surface energy reaches the lowest value for the blended film with 70% of RPS, which may be caused by the different roughness measurements for LPS film, RPS film and the blended films. The viscosities of these films are obtained through the radii of the dewetting holes, the dewetting velocities, the widths of the rims and the receding contact angles along dewetting process. Results show LPS film has a lower viscosity than RPS film. The viscosities of the blended films fall in between those of LPS film and RPS film, and increase with increasing RPS concentration. Moreover, the experimental viscosities of the blended films present lower values than those calculated from the pure-component viscosity using a binary mixing rule. The ratio of the experimental viscosity to the calculated viscosity reaches a lowest value with 70% of RPS. This may be attributed to the efficient packing ability of the ring chains, the effect of chain threading and the amount of free volume in the film.
2018, 0(6): 748-754
doi: 10.11777/j.issn1000-3304.2017.17246
Abstract:
Semicrystalline polymers are composed of crystalline and amorphous regions. The crystalline region plays a key role in determining their mechanical properties by providing stiff crosslinking domains. Understanding how the microscopic mechanical properties of the polymer single crystals are related to their macroscopic mechanical properties is significant to reveal the fundamental elastic and plastic deformations for advanced polymer engineering materials. The study of mesoscopic mechanical properties of polymer single crystal is key to this issue. Here, by using atomic force microscopy (AFM) imaging and force spectroscopy together, the mesoscopic mechanical properties of PEO single-crystal were investigated by squeezing PEO molecules out of the crystal phase using AFM tip. After elastically deformed, PEO single-crystal layer was penetrated by AFM tip at several tens of nN.The breakthrough force increased with the increase of the tip radius and PEO-solvent interfacial energy. The breakthrough force shows a linear correlation with the logarithm of the approaching velocity, which is fitted very well by molecular model. The energy for squeezing PEO chains out of their single crystal corresponds to the area enclosed by the approaching and retracting curves. Moreover, the energy for pulling a single PEO chain from its single crystal is calculated from the typical pulling curves. The energy for squeezing a same number of PEO chains out of their single crystal is about 23.4% lower than pulling. This energy comparison is helpful for bridging the microscopic and the mesoscopic mechanical properties. These results indicate that the combined techniques represent a novel experimental tool to investigate mesoscopic mechanical properties of the polymer materials in their condensed states.
Semicrystalline polymers are composed of crystalline and amorphous regions. The crystalline region plays a key role in determining their mechanical properties by providing stiff crosslinking domains. Understanding how the microscopic mechanical properties of the polymer single crystals are related to their macroscopic mechanical properties is significant to reveal the fundamental elastic and plastic deformations for advanced polymer engineering materials. The study of mesoscopic mechanical properties of polymer single crystal is key to this issue. Here, by using atomic force microscopy (AFM) imaging and force spectroscopy together, the mesoscopic mechanical properties of PEO single-crystal were investigated by squeezing PEO molecules out of the crystal phase using AFM tip. After elastically deformed, PEO single-crystal layer was penetrated by AFM tip at several tens of nN.The breakthrough force increased with the increase of the tip radius and PEO-solvent interfacial energy. The breakthrough force shows a linear correlation with the logarithm of the approaching velocity, which is fitted very well by molecular model. The energy for squeezing PEO chains out of their single crystal corresponds to the area enclosed by the approaching and retracting curves. Moreover, the energy for pulling a single PEO chain from its single crystal is calculated from the typical pulling curves. The energy for squeezing a same number of PEO chains out of their single crystal is about 23.4% lower than pulling. This energy comparison is helpful for bridging the microscopic and the mesoscopic mechanical properties. These results indicate that the combined techniques represent a novel experimental tool to investigate mesoscopic mechanical properties of the polymer materials in their condensed states.
2018, 0(6): 755-764
doi: 10.11777/j.issn1000-3304.2017.17226
Abstract:
Polyacrylonitrile (PAN) precursor nanofibers are prepared by traditional electrospinning and the centrifugal spinning, respectively. The nanofiber bundles are drawn in hot air with a constant force into 1 and 3 times of the original length. Subsequently, the crystalline structure, orientation, morphology, diameter of PAN nanofibers before and after drawing treatment were characterized by WAXD and SEM. The results show that: (1) the efficiency of centrifugal-electrospinning is far higher (120 times) than that of electrospinning (fluid flow rate of centrifugal-electrospinning: 2 mL/min, fluid flow rate of electrospinning: 1 mL/h). (2) Despite a low crystallinity from centrifugal spinning or electrospinning (the crystallinity of the PAN nanofiber precursor by centrifugal spinning is 25%, while that by electrospinning is 10.6%). PAN precursor nanofibers prepared by centrifugal spinning have certain orientation (60.5%); while those prepared by electrospinning have almost no orientation; (3) Hot-air-drawing with a constant force (1.00 N) contributes to a higher crystallinity (centrifugal spinning: 45.8%, electrospinning: 36.2%) and orientation (centrifugal spinning: 72.5%, electrospinning: 59.8%) for the PAN nanofibers. Moreover, increased drawing temperature and force results in a decrease in the diameter of the PAN nanofiber bundles (the diameter of PAN nanofibers prepared by centrifugal spinning decreases from 675 nm to 510 nm; while that by electrospinning decreases from 460 nm to 355 nm). Compared with the slight effect of the spinning process on crystalline structure and orientation, the hot-air drawing treatment significantly promotes the crystalline and orientation. The centrifugal force is helpful to eliminate the whip phenomenon and to make a full drawing of jet flow, finally leading to a higher certain orientation for the polymer chains of PAN nanofibers.
Polyacrylonitrile (PAN) precursor nanofibers are prepared by traditional electrospinning and the centrifugal spinning, respectively. The nanofiber bundles are drawn in hot air with a constant force into 1 and 3 times of the original length. Subsequently, the crystalline structure, orientation, morphology, diameter of PAN nanofibers before and after drawing treatment were characterized by WAXD and SEM. The results show that: (1) the efficiency of centrifugal-electrospinning is far higher (120 times) than that of electrospinning (fluid flow rate of centrifugal-electrospinning: 2 mL/min, fluid flow rate of electrospinning: 1 mL/h). (2) Despite a low crystallinity from centrifugal spinning or electrospinning (the crystallinity of the PAN nanofiber precursor by centrifugal spinning is 25%, while that by electrospinning is 10.6%). PAN precursor nanofibers prepared by centrifugal spinning have certain orientation (60.5%); while those prepared by electrospinning have almost no orientation; (3) Hot-air-drawing with a constant force (1.00 N) contributes to a higher crystallinity (centrifugal spinning: 45.8%, electrospinning: 36.2%) and orientation (centrifugal spinning: 72.5%, electrospinning: 59.8%) for the PAN nanofibers. Moreover, increased drawing temperature and force results in a decrease in the diameter of the PAN nanofiber bundles (the diameter of PAN nanofibers prepared by centrifugal spinning decreases from 675 nm to 510 nm; while that by electrospinning decreases from 460 nm to 355 nm). Compared with the slight effect of the spinning process on crystalline structure and orientation, the hot-air drawing treatment significantly promotes the crystalline and orientation. The centrifugal force is helpful to eliminate the whip phenomenon and to make a full drawing of jet flow, finally leading to a higher certain orientation for the polymer chains of PAN nanofibers.
2018, 0(6): 765-772
doi: 10.11777/j.issn1000-3304.2017.17322
Abstract:
It is known that the solubility of PB-1 in n-heptane correlates closly to temperature, so it is thus of vital importance to investigate the solution crystallization of polybutene-1 (PB-1) and polybutene-1 in-reactor alloy (PBA) via the cooling solution crystallization method. In this work, the isothermal solution crystallization behaviors of PB-1 and PB-1 in-reactor alloy (PBA) from n-heptane were investigated. The dissolution temperature and isothermal crystallization temperature were determined from the solubility curves of PB-1 in n-heptane obtained by grametry. The isothermal crystallization kinetics of PB-1 and PBA from solutions were studied by dilatometry. The solution crystallization rate decreased with increasing isothermal temperature without changing the nucleation mode of PB-1. However, the crystallization rate of PB-1 component in PBA was faster than that of pure PB-1. The presence of polypropylene (PP) component in PBA shortened nucleation induction period of PB-1 component, and PB-b-PP copolymer could accelerate crystallization rate of PB-1 component. Additionally, the DSC test confirmed that the crystal form I′ and III of PB-1 were generated during the solution crystallization in both pure PB-1 and PBA, and no crystal form transformation occurred at room temperature. Due to the solvation of n-heptane, the two crystal forms I and II of PB-1 were not observed in this system. From WAXD measurement, it has also been found that the increase in solution crystallization temperature promoted the relative content of the crystal form III with a decrease in the crystallinity of PB-1. This was because that the increase in temperature led to decrease in supersaturation of solution system, which weakened the driving force of the crystallization and decreased the crystallizable component of PB-1. The behavior change of PB-1 component in PBA with temperature was similar to that of pure PB-1. At the same temperature, the presence of PP component in PBA promoted the III/I′ ratio and the crystallinity of PB-1. We further proposed the crystallization models for PB-1 and PBA in solutions.
It is known that the solubility of PB-1 in n-heptane correlates closly to temperature, so it is thus of vital importance to investigate the solution crystallization of polybutene-1 (PB-1) and polybutene-1 in-reactor alloy (PBA) via the cooling solution crystallization method. In this work, the isothermal solution crystallization behaviors of PB-1 and PB-1 in-reactor alloy (PBA) from n-heptane were investigated. The dissolution temperature and isothermal crystallization temperature were determined from the solubility curves of PB-1 in n-heptane obtained by grametry. The isothermal crystallization kinetics of PB-1 and PBA from solutions were studied by dilatometry. The solution crystallization rate decreased with increasing isothermal temperature without changing the nucleation mode of PB-1. However, the crystallization rate of PB-1 component in PBA was faster than that of pure PB-1. The presence of polypropylene (PP) component in PBA shortened nucleation induction period of PB-1 component, and PB-b-PP copolymer could accelerate crystallization rate of PB-1 component. Additionally, the DSC test confirmed that the crystal form I′ and III of PB-1 were generated during the solution crystallization in both pure PB-1 and PBA, and no crystal form transformation occurred at room temperature. Due to the solvation of n-heptane, the two crystal forms I and II of PB-1 were not observed in this system. From WAXD measurement, it has also been found that the increase in solution crystallization temperature promoted the relative content of the crystal form III with a decrease in the crystallinity of PB-1. This was because that the increase in temperature led to decrease in supersaturation of solution system, which weakened the driving force of the crystallization and decreased the crystallizable component of PB-1. The behavior change of PB-1 component in PBA with temperature was similar to that of pure PB-1. At the same temperature, the presence of PP component in PBA promoted the III/I′ ratio and the crystallinity of PB-1. We further proposed the crystallization models for PB-1 and PBA in solutions.
