Login In
2018 Volume 36 Issue 4
2018, 36(4):
Abstract:
2018, 36(4): 425-444
doi: 10.1007/s10118-018-2070-6
Abstract:
Synthetic two-dimensional (2D) polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2D structures bring superior properties. Although, from linear to 2D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2D materials from three respects:(1) Chemistry-different types of polymerization reactions or supramolecular assembly to construct the 2D networks were described; (2) Preparation methods-surface science, crystal engineering approaches and solution synthesis were introduced; (3) Functionalization and some early applications.
Synthetic two-dimensional (2D) polymers have totally different topology structures compared with traditional linear or branched polymers. The peculiar 2D structures bring superior properties. Although, from linear to 2D polymers, the study of these new materials is still in its infancy, they already show potential applications especially in optoelectronics, membranes, energy storage and catalysis, etc. In this review, we summarize the recent progress of the 2D materials from three respects:(1) Chemistry-different types of polymerization reactions or supramolecular assembly to construct the 2D networks were described; (2) Preparation methods-surface science, crystal engineering approaches and solution synthesis were introduced; (3) Functionalization and some early applications.
2018, 36(4): 445-461
doi: 10.1007/s10118-018-2045-7
Abstract:
Carbon nanotubes (CNTs) have long been recognized as the stiffest and strongest man-made material known to date. In addition, their high electrical conductivity has roused interest in the areas of electrical appliances and communication related applications. However, due to their miniature size, the excellent properties of these nanostructures can only be exploited if they are homogeneously embedded into light-weight matrices as those offered by a whole series of engineering polymers. In order to enhance their chemical affinity to engineering polymer matrices, chemical modification of the graphitic sidewalls and tips is necessary. The mechanical and electrical properties to date of a whole range of nanocomposites of various carbon nanotube contents are also reviewed in this attempt to facilitate progress in this emerging area. Recently, carbonaceous nano-fillers such as graphene and carbon nanotubes (CNTs) play a promising role due to their better structural and functional properties and broad range of applications in every field. Since CNTs usually form stabilized bundles due to van der Waals interactions, they are extremely difficult to disperse and align in a polymer matrix. The biggest issues in the preparation of CNTs reinforced composites reside in efficient dispersion of CNTs into a polymer matrix, the assessment of the dispersion, and the alignment and control of the CNTs in the matrix. An overview of various CNT functionalization methods is given. In particular, CNT functionalization using click chemistry and the preparation of CNT composites employing hyperbranched polymers are stressed as potential techniques to achieve good CNT dispersion. In addition, discussions on mechanical, thermal, electrical, electrochemical and applications of polymer/CNT composites are also included.
Carbon nanotubes (CNTs) have long been recognized as the stiffest and strongest man-made material known to date. In addition, their high electrical conductivity has roused interest in the areas of electrical appliances and communication related applications. However, due to their miniature size, the excellent properties of these nanostructures can only be exploited if they are homogeneously embedded into light-weight matrices as those offered by a whole series of engineering polymers. In order to enhance their chemical affinity to engineering polymer matrices, chemical modification of the graphitic sidewalls and tips is necessary. The mechanical and electrical properties to date of a whole range of nanocomposites of various carbon nanotube contents are also reviewed in this attempt to facilitate progress in this emerging area. Recently, carbonaceous nano-fillers such as graphene and carbon nanotubes (CNTs) play a promising role due to their better structural and functional properties and broad range of applications in every field. Since CNTs usually form stabilized bundles due to van der Waals interactions, they are extremely difficult to disperse and align in a polymer matrix. The biggest issues in the preparation of CNTs reinforced composites reside in efficient dispersion of CNTs into a polymer matrix, the assessment of the dispersion, and the alignment and control of the CNTs in the matrix. An overview of various CNT functionalization methods is given. In particular, CNT functionalization using click chemistry and the preparation of CNT composites employing hyperbranched polymers are stressed as potential techniques to achieve good CNT dispersion. In addition, discussions on mechanical, thermal, electrical, electrochemical and applications of polymer/CNT composites are also included.
2018, 36(4): 462-471
doi: 10.1007/s10118-018-2063-5
Abstract:
A novel Ni(Ⅱ) ion-imprinted silica gel polymer was prepared via the surface imprinting technique combined with aqueous solution polymerization by using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as a functional monomer for the selective separation of Ni(Ⅱ) from aqueous solution. The sorbent showed good chemical and thermal stability. Kinetics studies indicated that the equilibrium adsorption was achieved within 10 min and the adsorption kinetics fitted well with the pseudo-second-order kinetic model. The maximum adsorption capacity of the ion-imprinted polymer towards Ni(Ⅱ) at the optimal pH of 7.0 was 66.22 mg·g-1. The relative selectivity coefficients of the sorbent were 9.23, 15.71, 14.72 and 20.15 for Ni(Ⅱ)/Co(Ⅱ), Ni(Ⅱ)/Cu(Ⅱ), Ni(Ⅱ)/Zn(Ⅱ) and Ni(Ⅱ)/Pb(Ⅱ), respectively. The adsorption isotherm fitted well with Langmuir isotherm model. The thermodynamic results indicated that the adsorption of Ni(Ⅱ) was a spontaneous and endothermic process. The sorbent showed good reusability evidenced by six cycles of adsorption/desorption experiments. The precision of this method is satisfactory. Thus, the prepared sorbent can be considered as a promising sorbent for selective separation of Ni(Ⅱ) in real water samples.
A novel Ni(Ⅱ) ion-imprinted silica gel polymer was prepared via the surface imprinting technique combined with aqueous solution polymerization by using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as a functional monomer for the selective separation of Ni(Ⅱ) from aqueous solution. The sorbent showed good chemical and thermal stability. Kinetics studies indicated that the equilibrium adsorption was achieved within 10 min and the adsorption kinetics fitted well with the pseudo-second-order kinetic model. The maximum adsorption capacity of the ion-imprinted polymer towards Ni(Ⅱ) at the optimal pH of 7.0 was 66.22 mg·g-1. The relative selectivity coefficients of the sorbent were 9.23, 15.71, 14.72 and 20.15 for Ni(Ⅱ)/Co(Ⅱ), Ni(Ⅱ)/Cu(Ⅱ), Ni(Ⅱ)/Zn(Ⅱ) and Ni(Ⅱ)/Pb(Ⅱ), respectively. The adsorption isotherm fitted well with Langmuir isotherm model. The thermodynamic results indicated that the adsorption of Ni(Ⅱ) was a spontaneous and endothermic process. The sorbent showed good reusability evidenced by six cycles of adsorption/desorption experiments. The precision of this method is satisfactory. Thus, the prepared sorbent can be considered as a promising sorbent for selective separation of Ni(Ⅱ) in real water samples.
2018, 36(4): 472-478
doi: 10.1007/s10118-018-2031-0
Abstract:
High sensitive immunoassay platforms have gained intense attention due to their vital roles in early-stage disease diagnosis and therapeutic information feedback. Although random covalent-binding of antibody has been widely adopted in immunoassays due to its simplicity and effectiveness, it readily loses its activity and fails to exhibit high antigen-binding capacity. In this work, copolymer of zwitterionic sulfobetaine methacrylate (SBMA) and glycidyl methacrylate (GMA) brushes were immobilized onto inert polypropylene (PP) via surface-initiated atom transfer radical polymerization (ATRP) based on biomimetic dopamine pretreatment. Subsequently, boronic acid (BA) groups were covalently bonded via active GMA units, followed by the introduction of oriented immobilization of antibody. Owing to the oriented immobilization of antibody facilitated by BA groups in polymer brush, the bioactivity of antibody is well preserved, which endows the surface with significantly enhanced antigen-binding capacity. Moreover, the existence of SBMA segments in polymer brushes renders the surface high resistance to nonspecific protein adsorption, significantly alleviating the signal interference of antigen recognition. This strategy could find potential applications in developing high sensitive immunoassay platforms based on the different substrates.
High sensitive immunoassay platforms have gained intense attention due to their vital roles in early-stage disease diagnosis and therapeutic information feedback. Although random covalent-binding of antibody has been widely adopted in immunoassays due to its simplicity and effectiveness, it readily loses its activity and fails to exhibit high antigen-binding capacity. In this work, copolymer of zwitterionic sulfobetaine methacrylate (SBMA) and glycidyl methacrylate (GMA) brushes were immobilized onto inert polypropylene (PP) via surface-initiated atom transfer radical polymerization (ATRP) based on biomimetic dopamine pretreatment. Subsequently, boronic acid (BA) groups were covalently bonded via active GMA units, followed by the introduction of oriented immobilization of antibody. Owing to the oriented immobilization of antibody facilitated by BA groups in polymer brush, the bioactivity of antibody is well preserved, which endows the surface with significantly enhanced antigen-binding capacity. Moreover, the existence of SBMA segments in polymer brushes renders the surface high resistance to nonspecific protein adsorption, significantly alleviating the signal interference of antigen recognition. This strategy could find potential applications in developing high sensitive immunoassay platforms based on the different substrates.
2018, 36(4): 479-487
doi: 10.1007/s10118-018-2009-y
Abstract:
In this study, a targeting micellar drug delivery system was developed for intravesical instilled chemotherapy of bladder cancer. The amphiphilic diblock copolymer poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEO) with functional amino group (NH2) at the end of PEO block was synthesized. Then the copolymer was conjugated with folic acid (FA) and fluorescein isothiocyannate (FITC) via the PEO-NH2 terminus, and then assembled into micelles with the target moiety and fluorescence labeling. In addition, drug loaded micelles were also fabricated with anticancer drug doxorubicin (DOX) encapsulated in the hydrophobic core. The micelles were characterized in terms of size, drug loaded efficiency and critical micellization concentration (CMC) by means of DLS, UV and fluorescence spectra. In vitro cellular uptake and cytotoxicity studies showed that FA modified PCL-b-PEO-FA micelles have a greater targeting efficiency to human bladder cancer cell (T-24 cell) compared to PCL-b-PEO-NH2 micelles due to the conjugation of FA on the surface, while no targeting effect to normal tissue originated human embryonic kidney 293 (HEK-293) cells was observed, enabling the micelles a promising drug carrier for intravesical instilled chemotherapy of bladder cancer.
In this study, a targeting micellar drug delivery system was developed for intravesical instilled chemotherapy of bladder cancer. The amphiphilic diblock copolymer poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEO) with functional amino group (NH2) at the end of PEO block was synthesized. Then the copolymer was conjugated with folic acid (FA) and fluorescein isothiocyannate (FITC) via the PEO-NH2 terminus, and then assembled into micelles with the target moiety and fluorescence labeling. In addition, drug loaded micelles were also fabricated with anticancer drug doxorubicin (DOX) encapsulated in the hydrophobic core. The micelles were characterized in terms of size, drug loaded efficiency and critical micellization concentration (CMC) by means of DLS, UV and fluorescence spectra. In vitro cellular uptake and cytotoxicity studies showed that FA modified PCL-b-PEO-FA micelles have a greater targeting efficiency to human bladder cancer cell (T-24 cell) compared to PCL-b-PEO-NH2 micelles due to the conjugation of FA on the surface, while no targeting effect to normal tissue originated human embryonic kidney 293 (HEK-293) cells was observed, enabling the micelles a promising drug carrier for intravesical instilled chemotherapy of bladder cancer.
2018, 36(4): 488-496
doi: 10.1007/s10118-018-2037-7
Abstract:
Self-consistent field theory (SCFT), as a state-of-the-art technique for studying the self-assembly of block copolymers, is attracting continuous efforts to improve its accuracy and efficiency. Here we present a fourth-order exponential time differencing Runge-Kutta algorithm (ETDRK4) to solve the modified diffusion equation (MDE) which is the most time-consuming part of a SCFT calculation. By making a careful comparison with currently most efficient and popular algorithms, we demonstrate that the ETDRK4 algorithm significantly reduces the number of chain contour steps in solving the MDE, resulting in a boost of the overall computation efficiency, while it shares the same spatial accuracy with other algorithms. In addition, to demonstrate the power of our ETDRK4 algorithm, we apply it to compute the phase boundaries of the bicontinuous gyroid phase in the strong segregation regime and to verify the existence of the triple point of the O70 phase, the lamellar phase and the cylindrical phase.
Self-consistent field theory (SCFT), as a state-of-the-art technique for studying the self-assembly of block copolymers, is attracting continuous efforts to improve its accuracy and efficiency. Here we present a fourth-order exponential time differencing Runge-Kutta algorithm (ETDRK4) to solve the modified diffusion equation (MDE) which is the most time-consuming part of a SCFT calculation. By making a careful comparison with currently most efficient and popular algorithms, we demonstrate that the ETDRK4 algorithm significantly reduces the number of chain contour steps in solving the MDE, resulting in a boost of the overall computation efficiency, while it shares the same spatial accuracy with other algorithms. In addition, to demonstrate the power of our ETDRK4 algorithm, we apply it to compute the phase boundaries of the bicontinuous gyroid phase in the strong segregation regime and to verify the existence of the triple point of the O70 phase, the lamellar phase and the cylindrical phase.
2018, 36(4): 497-504
doi: 10.1007/s10118-018-2026-x
Abstract:
Hydroxy-containing low molecular weight poly(2,6-dimethyl-1,4-phenylene oxide) (rPPO) and self-promoted hydroxy-containing phthalonitrile (HPPH) were prepared by redistribution reaction and the simple nucleophilic displacement of a nitro-substituent from 4-nitrophthalonitrile in a dipolar aprotic solvent respectively. The hydroxy-containing phthalonitriles modified by rPPO were prepared by mechanical blending without compatibilizer, followed by heating. The curing behavior was studied using dynamic rheological analysis, and the results showed that the rPPO-modified phthalonitrile exhibited a large processing window (over -67℃) and complex viscosity (0.18-0.8 Pa·s) at moderate temperatures. After curing at 300℃, the resulting polymers showed good thermal stability and high modulus as observed by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The dielectric properties and the morphology of rPPO-modified phthalonitrile networks were studied by dielectric analysis and field-emission scanning electron microscopy (SEM).
Hydroxy-containing low molecular weight poly(2,6-dimethyl-1,4-phenylene oxide) (rPPO) and self-promoted hydroxy-containing phthalonitrile (HPPH) were prepared by redistribution reaction and the simple nucleophilic displacement of a nitro-substituent from 4-nitrophthalonitrile in a dipolar aprotic solvent respectively. The hydroxy-containing phthalonitriles modified by rPPO were prepared by mechanical blending without compatibilizer, followed by heating. The curing behavior was studied using dynamic rheological analysis, and the results showed that the rPPO-modified phthalonitrile exhibited a large processing window (over -67℃) and complex viscosity (0.18-0.8 Pa·s) at moderate temperatures. After curing at 300℃, the resulting polymers showed good thermal stability and high modulus as observed by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The dielectric properties and the morphology of rPPO-modified phthalonitrile networks were studied by dielectric analysis and field-emission scanning electron microscopy (SEM).
2018, 36(4): 505-513
doi: 10.1007/s10118-018-2019-9
Abstract:
There has been controversy as to whether the addition of nanoparticles to a polymer melt causes perturbed chain structure of polymers. In this work, the chain conformations of polydimethylsiloxane (PDMS) with addition of polyhedral oligomeric silsesquioxane (POSS) nanoparticles have been studied using a classical density functional approach. Under the strong interactions of POSS-PDMS, the radius of gyration of PDMS in the nanocomposites can either increase or decline depending on particle loading. After adding nanoparticles with larger size or weaker interactions, both the increasing and the declining amplitudes can be largely suppressed. The results provide a deep understanding of chain conformation in polymer nanocomposites.
There has been controversy as to whether the addition of nanoparticles to a polymer melt causes perturbed chain structure of polymers. In this work, the chain conformations of polydimethylsiloxane (PDMS) with addition of polyhedral oligomeric silsesquioxane (POSS) nanoparticles have been studied using a classical density functional approach. Under the strong interactions of POSS-PDMS, the radius of gyration of PDMS in the nanocomposites can either increase or decline depending on particle loading. After adding nanoparticles with larger size or weaker interactions, both the increasing and the declining amplitudes can be largely suppressed. The results provide a deep understanding of chain conformation in polymer nanocomposites.
2018, 36(4): 514-520
doi: 10.1007/s10118-018-2020-3
Abstract:
Thermomechanical properties of polyurethanes (PUs) strongly depend on the molecular interactions and microphase structure. In this work, two chain extenders with different ratios, flexile 1, 4-butanediol (BDO) and branched trimethylolpropane mono allyl ether (TMPAE), are used to tune the molecular interactions and microphase structures of a series of biodegradable thermoplastic polyurethanes (TPUs). In TPUs, the biodegradable polycaprolactone (PCL, Mn of 2000) is used as soft segment while 1, 6-diisocyanatohexane (HDI) and chain extenders are used as hard segment. Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscppy (1H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and mechanical tests were performed to characterize the bulk structure and properties of TPUs. Compared with BDO, the steric bulk of TMPAE is larger. The increment of TMPAE can help to increase the hydrogen bond content, microphase separation, and the elastic modulus ratio (R), which would strongly affect the thermomechanical property of the TPUs. The results of this work verify the importance of the structure of chain extender on the properties of TPUs. It provides valuable information for further understanding the structure-property relationships of these polyurethanes.
Thermomechanical properties of polyurethanes (PUs) strongly depend on the molecular interactions and microphase structure. In this work, two chain extenders with different ratios, flexile 1, 4-butanediol (BDO) and branched trimethylolpropane mono allyl ether (TMPAE), are used to tune the molecular interactions and microphase structures of a series of biodegradable thermoplastic polyurethanes (TPUs). In TPUs, the biodegradable polycaprolactone (PCL, Mn of 2000) is used as soft segment while 1, 6-diisocyanatohexane (HDI) and chain extenders are used as hard segment. Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscppy (1H-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and mechanical tests were performed to characterize the bulk structure and properties of TPUs. Compared with BDO, the steric bulk of TMPAE is larger. The increment of TMPAE can help to increase the hydrogen bond content, microphase separation, and the elastic modulus ratio (R), which would strongly affect the thermomechanical property of the TPUs. The results of this work verify the importance of the structure of chain extender on the properties of TPUs. It provides valuable information for further understanding the structure-property relationships of these polyurethanes.
2018, 36(4): 521-527
doi: 10.1007/s10118-018-2048-4
Abstract:
In this paper, we combined high-end cationic UV-curable material with fluorinated chain obtaining a series of new fluorine-containing aromatic oxetane monomers via a mild nucleophilic substitution reaction. The structures and properties of monomers were characterized using 1H-NMR, 19F-NMR, dynamic viscosity tests and differential scanning calorimetry (DSC). It was determined that all of the fluorinated monomers obtained had much lower viscosity and higher thermostability after the introduction of hexafluorobenzene. Then, UV-curable coatings were prepared using four fluorine-containing aromatic oxetane monomers (FOX1-4); the UV-curing kinetics, with three kinds of initiators, and properties of the cured films were evaluated using real-time Fourier transform infrared (FTIR) spectroscopy, water and diiodomethane contact angle tests, surface energy calculations and scanning electron microscopy (SEM). The FTIR spectroscopy results showed that the coatings possessed excellent conversion rate (> 99% with liquid initiator PAG-201 in 150 s), and as the fluorine content increased, the monomers exhibited decreased mobility with the increasing viscosity and worse solubility with fluorinated monomers, resulting in a lower conversion rate. Moreover, the coatings possessed favorable hydrophobic and oleophobic properties and low surface energies owing to the fluoride chains floating to the membrane-air interface, which was also confirmed by discrete concave structures in SEM images. These new kinds of monomers can replace traditional fluorinated cationic monomers applied to the fingerprint resistant, fouling resistant, scratch resistant and anti-aging coatings, adhesives or printing ink materials.
In this paper, we combined high-end cationic UV-curable material with fluorinated chain obtaining a series of new fluorine-containing aromatic oxetane monomers via a mild nucleophilic substitution reaction. The structures and properties of monomers were characterized using 1H-NMR, 19F-NMR, dynamic viscosity tests and differential scanning calorimetry (DSC). It was determined that all of the fluorinated monomers obtained had much lower viscosity and higher thermostability after the introduction of hexafluorobenzene. Then, UV-curable coatings were prepared using four fluorine-containing aromatic oxetane monomers (FOX1-4); the UV-curing kinetics, with three kinds of initiators, and properties of the cured films were evaluated using real-time Fourier transform infrared (FTIR) spectroscopy, water and diiodomethane contact angle tests, surface energy calculations and scanning electron microscopy (SEM). The FTIR spectroscopy results showed that the coatings possessed excellent conversion rate (> 99% with liquid initiator PAG-201 in 150 s), and as the fluorine content increased, the monomers exhibited decreased mobility with the increasing viscosity and worse solubility with fluorinated monomers, resulting in a lower conversion rate. Moreover, the coatings possessed favorable hydrophobic and oleophobic properties and low surface energies owing to the fluoride chains floating to the membrane-air interface, which was also confirmed by discrete concave structures in SEM images. These new kinds of monomers can replace traditional fluorinated cationic monomers applied to the fingerprint resistant, fouling resistant, scratch resistant and anti-aging coatings, adhesives or printing ink materials.
2018, 36(4): 528-535
doi: 10.1007/s10118-018-2013-2
Abstract:
Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length (degree of polymerization) and grafting density (grafting chains per membrane area) was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl) ammonium hydroxide} (PMEDSAH), the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.
Branch length and density have critical effects on membrane performances; however, it is regarded to be traditionally difficult to investigate the relationship due to the uncontrolled membrane modification methods. In this study, zwitterionic polymer with controlled grafting branch chain length (degree of polymerization) and grafting density (grafting chains per membrane area) was tethered to the microporous polypropylene membrane surface based on the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization technique with click reaction. The modified membranes were tested by filtrating protein dispersion to highlight the correlations of branch chain length and grafting density with the membrane permeation performances. The pure water flux, the flux recovery ratio are positively and significantly, and the irreversible fouling negatively and significantly correlated with grafting density. These results demonstrate that the larger the coverage of the membrane with poly{[2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl) ammonium hydroxide} (PMEDSAH), the higher the pure water flux and the higher the flux recover ratio, and the lower the irreversible fouling, which shows that high grafting density is favorable to fouling reducing.
2018, 36(4): 536-545
doi: 10.1007/s10118-018-2029-7
Abstract:
In this work, four samples containing different contents of fumed SiO2 were prepared to improve the pore size distribution and various properties of β nucleated isotatic polypropylene (β-iPP) biaxial membrane used for lithium-ion battery separator. The wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) results show that the fumed SiO2 promotes the formation of β-crystal slightly and narrows down the thickness distribution of β-lamellae; meanwhile, evenly distributed SiO2 within β-iPP can be inspected by scanning electron microscopy (SEM). Moreover, further detailed characterization of morphological evolutions during biaxial stretching by tensile testing and SEM manifests that SiO2 can strengthen β-iPP and make the samples deform more homogeneously, resulting in a gradually elaborate and finer oriented microfibril structure after longitudinal stretching, in which more uniform defects distribute between fibrils and restrain the formation of coarse fibrils effectively. Therefore, more superior microporous structure emerges with the addition of SiO2, accompanied by narrower pore size distribution and better connectivity between microvoids, which is confirmed by mercury porosimeter and diminished Gurley value. Moreover, the lower thermal shrinkage, decreased shrinkage rate and suppressed porosity reduction indicate that fumed SiO2 improves thermal and dimensional stability of membrane dramatically. Furthermore, due to the excellent wettability of SiO2 with electrolyte, the microporous membranes doped with SiO2 have higher electrolyte uptake, even after heat treatment at elevated temperature.
In this work, four samples containing different contents of fumed SiO2 were prepared to improve the pore size distribution and various properties of β nucleated isotatic polypropylene (β-iPP) biaxial membrane used for lithium-ion battery separator. The wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) results show that the fumed SiO2 promotes the formation of β-crystal slightly and narrows down the thickness distribution of β-lamellae; meanwhile, evenly distributed SiO2 within β-iPP can be inspected by scanning electron microscopy (SEM). Moreover, further detailed characterization of morphological evolutions during biaxial stretching by tensile testing and SEM manifests that SiO2 can strengthen β-iPP and make the samples deform more homogeneously, resulting in a gradually elaborate and finer oriented microfibril structure after longitudinal stretching, in which more uniform defects distribute between fibrils and restrain the formation of coarse fibrils effectively. Therefore, more superior microporous structure emerges with the addition of SiO2, accompanied by narrower pore size distribution and better connectivity between microvoids, which is confirmed by mercury porosimeter and diminished Gurley value. Moreover, the lower thermal shrinkage, decreased shrinkage rate and suppressed porosity reduction indicate that fumed SiO2 improves thermal and dimensional stability of membrane dramatically. Furthermore, due to the excellent wettability of SiO2 with electrolyte, the microporous membranes doped with SiO2 have higher electrolyte uptake, even after heat treatment at elevated temperature.
2018, 36(4): 546-554
doi: 10.1007/s10118-018-2017-y
Abstract:
Green light-emitting polyfluorenes containing 3, 7-bis(4-hexylthiophen-2-yl)dibenzo[b, d]thiophene 5, 5-dioxide (DHTSO) unit were synthesized. All the resulted polymers show high thermal stability with the decomposition temperatures (Td) over 420℃ and the glass transition temperatures (Tg) over 75℃. The polymers exhibit the enhanced highest occupied molecular orbital (HOMO) energy levels and the depressed lowest unoccupied molecular orbital (LUMO) energy levels with the increase of DHTSO unit in polymers. The photoluminescence (PL) spectra of the polymers show positive solvatochromism in solution with the variation of solution polarities, indicating remarkable intramolecular charge transfer (ICT) effect in the polymers containing DHTSO moiety. The fluorescence quantum yields (φPL) are in the range of 34%-67% for PF-DHTSOs in film. All polymers possess two photon absorption (TPA) properties, and the TPA cross sections (δ2) are enhanced with increasing DHTSO unit in polymers. The highest δ2 is 2392 GM for PF-DHTSO15 in chloroform solution upon 740 nm excitation. The device of PF-DHTSO15 shows green emission with the Commission Internationale de L'. Eclairage (CIE) coordinates of (0.26, 0.59), and the maximum luminous efficiency (LEmax) of 10.8 cd·A-1 with the configuration of ITO/PEDOT:PSS/EL/CsF/Al. These results indicate that introducing DHTSO unit into polyfluorene backbone could be a promising molecular design strategy for TPA and effective green-light emission.
Green light-emitting polyfluorenes containing 3, 7-bis(4-hexylthiophen-2-yl)dibenzo[b, d]thiophene 5, 5-dioxide (DHTSO) unit were synthesized. All the resulted polymers show high thermal stability with the decomposition temperatures (Td) over 420℃ and the glass transition temperatures (Tg) over 75℃. The polymers exhibit the enhanced highest occupied molecular orbital (HOMO) energy levels and the depressed lowest unoccupied molecular orbital (LUMO) energy levels with the increase of DHTSO unit in polymers. The photoluminescence (PL) spectra of the polymers show positive solvatochromism in solution with the variation of solution polarities, indicating remarkable intramolecular charge transfer (ICT) effect in the polymers containing DHTSO moiety. The fluorescence quantum yields (φPL) are in the range of 34%-67% for PF-DHTSOs in film. All polymers possess two photon absorption (TPA) properties, and the TPA cross sections (δ2) are enhanced with increasing DHTSO unit in polymers. The highest δ2 is 2392 GM for PF-DHTSO15 in chloroform solution upon 740 nm excitation. The device of PF-DHTSO15 shows green emission with the Commission Internationale de L'. Eclairage (CIE) coordinates of (0.26, 0.59), and the maximum luminous efficiency (LEmax) of 10.8 cd·A-1 with the configuration of ITO/PEDOT:PSS/EL/CsF/Al. These results indicate that introducing DHTSO unit into polyfluorene backbone could be a promising molecular design strategy for TPA and effective green-light emission.
