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2017 Volume 35 Issue 5
2017, 35(5): 581-601
doi: 10.1007/s10118-017-1925-6
Abstract:
Triggered by environmental concerns and the rising demands for metal-free polymers in e.g. bio-related and microelectronic applications, studies on organocatalytic polymerization have been launched and developed unprecedentedly during the last 15 years. A wide range of organic molecules are now available in polymer chemists' toolbox to choose from as catalysts for polymerization of (hetero) cyclic and polar vinyl monomers. Apart from the intrinsic merits such as lower toxicity and better solubility compared with (transition) metal catalysts/initiators, organocatalysts have also shown, in many cases, excellence to achieve high polymerization rates and/or good control (selectivity). In addition, particular natures and catalytic/activating mechanisms of organocatalysts have led to new opportunities for rational design and efficient synthesis of macromolecular architectures, i.e. chain structures, topological structures and functionalities. This mini-review is specially themed on pathways to construct copolymer chain structures by organocatalytic copolymerization of mixed type monomers (comonomers bearing different polymerizing moieties) and will be sectioned by different comonomer combinations, including cyclic monoesters of different sizes, cyclic monoesters and lactides, cyclic esters and cyclic carbonates or epoxides, heterocycles and vinyl monomers.
Triggered by environmental concerns and the rising demands for metal-free polymers in e.g. bio-related and microelectronic applications, studies on organocatalytic polymerization have been launched and developed unprecedentedly during the last 15 years. A wide range of organic molecules are now available in polymer chemists' toolbox to choose from as catalysts for polymerization of (hetero) cyclic and polar vinyl monomers. Apart from the intrinsic merits such as lower toxicity and better solubility compared with (transition) metal catalysts/initiators, organocatalysts have also shown, in many cases, excellence to achieve high polymerization rates and/or good control (selectivity). In addition, particular natures and catalytic/activating mechanisms of organocatalysts have led to new opportunities for rational design and efficient synthesis of macromolecular architectures, i.e. chain structures, topological structures and functionalities. This mini-review is specially themed on pathways to construct copolymer chain structures by organocatalytic copolymerization of mixed type monomers (comonomers bearing different polymerizing moieties) and will be sectioned by different comonomer combinations, including cyclic monoesters of different sizes, cyclic monoesters and lactides, cyclic esters and cyclic carbonates or epoxides, heterocycles and vinyl monomers.
2017, 35(5): 602-610
doi: 10.1007/s10118-017-1921-x
Abstract:
This work reports a SO2 derivative-detecting and colorful hyperbranched polymeric ionic liquid (HBPIL) vesicle through aqueous self-assembly. By a simple anion-exchange, we achieved the combination of functional small-molecule probe of acid fuchsin with HBPILs. The obtained HBPIL vesicle displayed ultraviolet absorption at 544 nm, and was used as a novel SO2 derivative sensor with high sensitivity and visualization. Due to the functional ion pairs enriching on the surface, the SO32- detection limit of the HBPILs vesicles was as low as 0.138 μmol/L, which was about 1.5 orders of magnitude lower than that of acid fuchsin.
This work reports a SO2 derivative-detecting and colorful hyperbranched polymeric ionic liquid (HBPIL) vesicle through aqueous self-assembly. By a simple anion-exchange, we achieved the combination of functional small-molecule probe of acid fuchsin with HBPILs. The obtained HBPIL vesicle displayed ultraviolet absorption at 544 nm, and was used as a novel SO2 derivative sensor with high sensitivity and visualization. Due to the functional ion pairs enriching on the surface, the SO32- detection limit of the HBPILs vesicles was as low as 0.138 μmol/L, which was about 1.5 orders of magnitude lower than that of acid fuchsin.
2017, 35(5): 611-622
doi: 10.1007/s10118-017-1926-5
Abstract:
Four novel polymers, poly (3, 6-9-decyl-carbazole-alt-1, 3-benzene) (PB13CZ), poly (3, 6-9-decyl-carbazole-alt-bis (4-phenyl) (phenyl) phosphine oxide) (PTPPO38CZ), poly (3, 6-9-decyl-carbazole-alt-2, 4-phenyl (diphenyl) phosphine oxide) (PTPPO13CZ) and poly (3, 6-9-decyl-carbazole-alt-bis (3-phenyl) (phenyl) phosphine oxide) (PTTPO27CZ) were synthesized, and their thermal, photophysical properties and device applications were further investigated to correlate the chemical structures with the photoelectric performance of bipolar host materials for phosphorescent organic light emitting diodes. All of them show high thermal stability as revealed by their high glass transition temperatures and thermal decomposition temperatures at 5% weight loss. These polymers have wide band gaps and relatively high triplet energy levels. As a result, the spin coating method was used to prepare the green phosphorescent organic light emitting diodes with polymers PTPPO38CZ, PTPPO13CZ and PTTPO27CZ as the typical host materials. The green device of polymer PTPPO38CZ as host material shows electroluminescent performance with maximum current efficiency of 2.16 cd·A-1, maximum external quantum efficiency of 0.7%, maximum brightness of 1475 cd·m-2 and reduced efficiency roll-off of 7.14% at 600 cd·m-2, which are much better than those of the same devices hosted by polymers PTTPO27CZ and PTPPO13CZ.
Four novel polymers, poly (3, 6-9-decyl-carbazole-alt-1, 3-benzene) (PB13CZ), poly (3, 6-9-decyl-carbazole-alt-bis (4-phenyl) (phenyl) phosphine oxide) (PTPPO38CZ), poly (3, 6-9-decyl-carbazole-alt-2, 4-phenyl (diphenyl) phosphine oxide) (PTPPO13CZ) and poly (3, 6-9-decyl-carbazole-alt-bis (3-phenyl) (phenyl) phosphine oxide) (PTTPO27CZ) were synthesized, and their thermal, photophysical properties and device applications were further investigated to correlate the chemical structures with the photoelectric performance of bipolar host materials for phosphorescent organic light emitting diodes. All of them show high thermal stability as revealed by their high glass transition temperatures and thermal decomposition temperatures at 5% weight loss. These polymers have wide band gaps and relatively high triplet energy levels. As a result, the spin coating method was used to prepare the green phosphorescent organic light emitting diodes with polymers PTPPO38CZ, PTPPO13CZ and PTTPO27CZ as the typical host materials. The green device of polymer PTPPO38CZ as host material shows electroluminescent performance with maximum current efficiency of 2.16 cd·A-1, maximum external quantum efficiency of 0.7%, maximum brightness of 1475 cd·m-2 and reduced efficiency roll-off of 7.14% at 600 cd·m-2, which are much better than those of the same devices hosted by polymers PTTPO27CZ and PTPPO13CZ.
2017, 35(5): 623-630
doi: 10.1007/s10118-017-1914-9
Abstract:
In this paper, microphase behavior of an ABC triblock copolymer, polystyrene-block-poly (2-vinylpyridine)-blockpoly (ethylene oxide), namely PS-b-P2VP-b-PEO, was systematically studied during spin-coating and solvent vapor annealing based on various parameters, including the types of the solvent, spin speed and thickness. The morphological features and the microdomain location of the different blocks were characterized by atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM). With increasing thickness, the order-order transition from nanopores array to the pattern of nanostripes was observed due to microdomain coarsening. These processes of pattern transformation were based on the selectivity of toluene for different blocks and on the contact time between solvent molecules and the three blocks. This work provides different templates for preparation of gold nanoparticle array on silicon wafer, which can be adopted as an active surface-enhanced Raman scattering (SERS) substrate for poly (3-hexylthiophene) (P3HT).
In this paper, microphase behavior of an ABC triblock copolymer, polystyrene-block-poly (2-vinylpyridine)-blockpoly (ethylene oxide), namely PS-b-P2VP-b-PEO, was systematically studied during spin-coating and solvent vapor annealing based on various parameters, including the types of the solvent, spin speed and thickness. The morphological features and the microdomain location of the different blocks were characterized by atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM). With increasing thickness, the order-order transition from nanopores array to the pattern of nanostripes was observed due to microdomain coarsening. These processes of pattern transformation were based on the selectivity of toluene for different blocks and on the contact time between solvent molecules and the three blocks. This work provides different templates for preparation of gold nanoparticle array on silicon wafer, which can be adopted as an active surface-enhanced Raman scattering (SERS) substrate for poly (3-hexylthiophene) (P3HT).
2017, 35(5): 631-640
doi: 10.1007/s10118-017-1924-7
Abstract:
Due to the various needs in the current applications, multifunctional composite materials with high strength and high toughness were highly desired now. Many scholars dedicated their time to find a simple, green and fast method for the preparation of multi-functional materials. In this study, inspired by the hierarchical "brick-and-mortar" structure and excellent mechanical performance of nacre, a fast green vacuum-filtration method was used to fabricate strong and multifunctional polyglutamic acid/layered double hydroxide (PGA/LDH) films mimicking nacre. The experimental results confirm that the artificial nacre has hierarchical "brick-and-mortar" structure. It exhibits excellent strength (93.5 MPa) and flexibility (easily bendable fold), combining with outstanding properties of UV-blocking and translucence properties. This work provides a way of fabricating multifunctional organic-inorganic hybrid films, which has potential applications in the areas of optical, transportation and construction fields.
Due to the various needs in the current applications, multifunctional composite materials with high strength and high toughness were highly desired now. Many scholars dedicated their time to find a simple, green and fast method for the preparation of multi-functional materials. In this study, inspired by the hierarchical "brick-and-mortar" structure and excellent mechanical performance of nacre, a fast green vacuum-filtration method was used to fabricate strong and multifunctional polyglutamic acid/layered double hydroxide (PGA/LDH) films mimicking nacre. The experimental results confirm that the artificial nacre has hierarchical "brick-and-mortar" structure. It exhibits excellent strength (93.5 MPa) and flexibility (easily bendable fold), combining with outstanding properties of UV-blocking and translucence properties. This work provides a way of fabricating multifunctional organic-inorganic hybrid films, which has potential applications in the areas of optical, transportation and construction fields.
2017, 35(5): 641-648
doi: 10.1007/s10118-017-1927-4
Abstract:
This contribution focuses on the impact of shear flow on size and nanostructure of PS-based amphiphilic block copolymer (BC) micelles by varying the stirring rate and copolymer composition. The results show that the vesicles formed from diblock copolymer (di-BC) of PS-b-PAA remain with vesicular morphology, although the average size decreases, with the increase of stirring rate. However, the multi-compartment micelles (MCMs) formed from tri-block copolymer (tri-BC) of PS-b-P2VP-b-PEO are quite intricate, in which the copolymer first self-assembles into spheres, then to clusters, to large compound micelles (LCMs), and finally back to spheres, as stirring rate increases from 100 r/min to 2200 r/min. Formation mechanism studies manifest that vesicles form simultaneously as water is added to the di-BC solution, termed as directassembly, and remain with vesicular structure in the flowing process. While for the PS-b-P2VP-b-PEO copolymer, spherical micelles at initial stage can further assemble into clusters and LCMs, termed as second-assembly, due to the speeding-upaggregation of the favorable stirring. As a result, an invert V-relationship between tri-BC micelle dimension and stirring rate is observed in contrast to the non-linear decreasing curve of di-BC vesicles. It is by investigating these various amphiphilic BCs that the understanding of shear dependence of size and morphology of micelles is improved from self-assembly to second-assembly process.
This contribution focuses on the impact of shear flow on size and nanostructure of PS-based amphiphilic block copolymer (BC) micelles by varying the stirring rate and copolymer composition. The results show that the vesicles formed from diblock copolymer (di-BC) of PS-b-PAA remain with vesicular morphology, although the average size decreases, with the increase of stirring rate. However, the multi-compartment micelles (MCMs) formed from tri-block copolymer (tri-BC) of PS-b-P2VP-b-PEO are quite intricate, in which the copolymer first self-assembles into spheres, then to clusters, to large compound micelles (LCMs), and finally back to spheres, as stirring rate increases from 100 r/min to 2200 r/min. Formation mechanism studies manifest that vesicles form simultaneously as water is added to the di-BC solution, termed as directassembly, and remain with vesicular structure in the flowing process. While for the PS-b-P2VP-b-PEO copolymer, spherical micelles at initial stage can further assemble into clusters and LCMs, termed as second-assembly, due to the speeding-upaggregation of the favorable stirring. As a result, an invert V-relationship between tri-BC micelle dimension and stirring rate is observed in contrast to the non-linear decreasing curve of di-BC vesicles. It is by investigating these various amphiphilic BCs that the understanding of shear dependence of size and morphology of micelles is improved from self-assembly to second-assembly process.
2017, 35(5): 649-658
doi: 10.1007/s10118-017-1918-5
Abstract:
Hydrogen bonding is considered to have significant effect on the interaction between polymeric chains and on the viscoelasticity of the polymeric materials. In this paper, we attempt to discuss the relationship between hydrogen bonding density and damping behavior and mechanical properties of polyethylene-based polymeric materials. For this reason, a series of pendant chain hydrogen bonding polymers (PCHBP) with different hydrogen bonding density (HBD) were prepared by quantitatively changing the content of pendent hydroxyl groups on the main chain of polyethylene. It was found that PCHBP with low HBD showed similar properties to polyethylene, indicating that the property of the materials was dependent mainly on the structure of the main chain. However, PCHBP with high HBD exhibited two tanδ peaks and a platform of loss modulus as well as a high storage modulus (about 400 MPa) at the second tanδ peak temperature, demonstrating that a polymeric material with high strength and damping properties was obtained. More importantly, the maximum of loss modulus showed a linear increase with the HBD, indicating that a higher HBD greatly improved the damping properties of the polymeric materials.
Hydrogen bonding is considered to have significant effect on the interaction between polymeric chains and on the viscoelasticity of the polymeric materials. In this paper, we attempt to discuss the relationship between hydrogen bonding density and damping behavior and mechanical properties of polyethylene-based polymeric materials. For this reason, a series of pendant chain hydrogen bonding polymers (PCHBP) with different hydrogen bonding density (HBD) were prepared by quantitatively changing the content of pendent hydroxyl groups on the main chain of polyethylene. It was found that PCHBP with low HBD showed similar properties to polyethylene, indicating that the property of the materials was dependent mainly on the structure of the main chain. However, PCHBP with high HBD exhibited two tanδ peaks and a platform of loss modulus as well as a high storage modulus (about 400 MPa) at the second tanδ peak temperature, demonstrating that a polymeric material with high strength and damping properties was obtained. More importantly, the maximum of loss modulus showed a linear increase with the HBD, indicating that a higher HBD greatly improved the damping properties of the polymeric materials.
2017, 35(5): 659-671
doi: 10.1007/s10118-017-1908-7
Abstract:
Polypropylene (PP) composites containing magnesium oxysulfate whisker (MOSw) or lauric acid (LA) modified MOSw (LAMOSw) were prepared via melt mixing in a torque rheometer. The heterogeneous nucleating effect of LAMOSw was clearly observed in polarized light microscopy (PLM) pictures with the presence of an abundance of small spherulites. MOSw exhibited no nucleation effect and formed a few spherulites with large size. Compared with PP/MOSw composites, PP/LAMOSw exhibited better impact strength, tensile strength and nominal strain at break, ascribing to three possible reasons: (ⅰ) more β-crystal PP formed, (ⅱ) better dispersity of LAMOSw in PP matrix and (ⅲ) the plasticizing effect of LA. The results of dynamic mechanical thermal analysis (DMTA) indicated that brittleness of the PP matrix at low temperature was improved by the addition of LAMOSw, while the interfacial interactions between MOSw and PP matrix were actually weakened by LA, as evidenced by the higher tanδ values over the entire range of test temperatures. In terms of the rheological properties of the composites, both the η* and G′ at low frequencies increase with the addition of MOSw or LAMOSw, indicating that the PP matrix was transformed from liquid-like to solid-like. However, a network of whiskers did not form because no plateau was found in the G′ at low frequencies. With low filler content, LAMOSw produced a stronger solid-like behavior than MOSw mainly due to the better dispersion of the LAMOSw in PP matrix. However, for highly-filled composites, the η* of PP/LAMOSw at low frequencies was smaller than that of PP/MOSw composite, since the particleparticle contact effect played a major role.
Polypropylene (PP) composites containing magnesium oxysulfate whisker (MOSw) or lauric acid (LA) modified MOSw (LAMOSw) were prepared via melt mixing in a torque rheometer. The heterogeneous nucleating effect of LAMOSw was clearly observed in polarized light microscopy (PLM) pictures with the presence of an abundance of small spherulites. MOSw exhibited no nucleation effect and formed a few spherulites with large size. Compared with PP/MOSw composites, PP/LAMOSw exhibited better impact strength, tensile strength and nominal strain at break, ascribing to three possible reasons: (ⅰ) more β-crystal PP formed, (ⅱ) better dispersity of LAMOSw in PP matrix and (ⅲ) the plasticizing effect of LA. The results of dynamic mechanical thermal analysis (DMTA) indicated that brittleness of the PP matrix at low temperature was improved by the addition of LAMOSw, while the interfacial interactions between MOSw and PP matrix were actually weakened by LA, as evidenced by the higher tanδ values over the entire range of test temperatures. In terms of the rheological properties of the composites, both the η* and G′ at low frequencies increase with the addition of MOSw or LAMOSw, indicating that the PP matrix was transformed from liquid-like to solid-like. However, a network of whiskers did not form because no plateau was found in the G′ at low frequencies. With low filler content, LAMOSw produced a stronger solid-like behavior than MOSw mainly due to the better dispersion of the LAMOSw in PP matrix. However, for highly-filled composites, the η* of PP/LAMOSw at low frequencies was smaller than that of PP/MOSw composite, since the particleparticle contact effect played a major role.
2017, 35(5): 672-680
doi: 10.1007/s10118-017-1912-y
Abstract:
The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 (iPP/TMB-5) were investigated by synchrotron radiation wide angel X-ray diffraction (SR-WAXD), differential scanning calorimeter (DSC) and polarized light microscope (PLM). It was found that α-crystallization lagged behind β-crystallization at normal temperatures, but the discrepancy reduced with increasing temperature. TMB-5 could not induce β - iPP when the nucleation agent is wrapped up with α-crystal that crystallized at high temperatures. The polymorphic composition of iPP/TMB-5 was susceptible to the introductory moment of shear. New crystallization process of β-nucleated iPP was proposed to understand the experimental phenomena which could not be explained by those reported in the literature. It was supposed that polymer crystallization initiated from mesophase, and the formations of iPP crystals involved the organization of helical conformation ordering within mesophase. It was proposed that the iPP melt contained mesophases with stereocomplex-type ordering of right-handed and left-handed helical chains which could be disturbed by shear or TMB-5, leading to different polymorphic structures.
The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 (iPP/TMB-5) were investigated by synchrotron radiation wide angel X-ray diffraction (SR-WAXD), differential scanning calorimeter (DSC) and polarized light microscope (PLM). It was found that α-crystallization lagged behind β-crystallization at normal temperatures, but the discrepancy reduced with increasing temperature. TMB-5 could not induce β - iPP when the nucleation agent is wrapped up with α-crystal that crystallized at high temperatures. The polymorphic composition of iPP/TMB-5 was susceptible to the introductory moment of shear. New crystallization process of β-nucleated iPP was proposed to understand the experimental phenomena which could not be explained by those reported in the literature. It was supposed that polymer crystallization initiated from mesophase, and the formations of iPP crystals involved the organization of helical conformation ordering within mesophase. It was proposed that the iPP melt contained mesophases with stereocomplex-type ordering of right-handed and left-handed helical chains which could be disturbed by shear or TMB-5, leading to different polymorphic structures.
2017, 35(5): 681-692
doi: 10.1007/s10118-017-1919-4
Abstract:
We present here the application of one-dimensional and two-dimensional NMR techniques to characterize the structure of methoxyl end-functionalized polystyrenes (PS). The peaks in 1H-NMR spectra corresponding to main-chain, side-chain and chain-end groups are assigned by 1H-1H gCOSY, 1H-13C gHSQC and gHMBC spectra. For the first time, the spin-lattice relaxation time (T1) of protons of the chain-ends is revealed to be affected more by polymer molecular weight (MW) than by the protons of the main-chains and the side-chains (almost independent from MW). As a result, a much higher delay time (d1) for chain-ends (d1 > 20T1) is needed for quantitative NMR measurement when using end-group estimation method to obtain the MW of PS, which is in accordance with the value estimated by GPC. An improved method for the polymer MW determination is established, by combination of different NMR techniques to distinguish the peaks, and a large d1 setting to achieve quantitative NMR analysis.
We present here the application of one-dimensional and two-dimensional NMR techniques to characterize the structure of methoxyl end-functionalized polystyrenes (PS). The peaks in 1H-NMR spectra corresponding to main-chain, side-chain and chain-end groups are assigned by 1H-1H gCOSY, 1H-13C gHSQC and gHMBC spectra. For the first time, the spin-lattice relaxation time (T1) of protons of the chain-ends is revealed to be affected more by polymer molecular weight (MW) than by the protons of the main-chains and the side-chains (almost independent from MW). As a result, a much higher delay time (d1) for chain-ends (d1 > 20T1) is needed for quantitative NMR measurement when using end-group estimation method to obtain the MW of PS, which is in accordance with the value estimated by GPC. An improved method for the polymer MW determination is established, by combination of different NMR techniques to distinguish the peaks, and a large d1 setting to achieve quantitative NMR analysis.
