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2013 Volume 31 Issue 6
2013, 31(6): 841-852
doi: 10.1007/s10118-013-1269-9
Abstract:
The dependence of properties on the structure and morphology of semicrystalline polymers offers an effective way to tailor the properties of these materials through structure control. To this end, establishing the structure and property relationship is of great importance. For a right characterization of the crystal structure, several techniques can be used. Among these techniques, electron diffraction has its advantage for determining the crystal structure related to specific formation condition since it can combine with bright and dark fields observation of the sample. This feature article describes the application of electron diffraction in determining the crystal structure of semicrystalline polymers with elaborately selected examples. We focus on how the electron diffraction can be used to disclose the crystal structure, mutual orientation of different crystals, as well as the disorders included in the polymer crystals.
The dependence of properties on the structure and morphology of semicrystalline polymers offers an effective way to tailor the properties of these materials through structure control. To this end, establishing the structure and property relationship is of great importance. For a right characterization of the crystal structure, several techniques can be used. Among these techniques, electron diffraction has its advantage for determining the crystal structure related to specific formation condition since it can combine with bright and dark fields observation of the sample. This feature article describes the application of electron diffraction in determining the crystal structure of semicrystalline polymers with elaborately selected examples. We focus on how the electron diffraction can be used to disclose the crystal structure, mutual orientation of different crystals, as well as the disorders included in the polymer crystals.
2013, 31(6): 853-869
doi: 10.1007/s10118-013-1287-7
Abstract:
Among the intrinsically conductive polymers, polyanilines have been of great interest in the past decades due to their wide applications in many fields, thanks to their reasonably good conductivity, easy preparation, and special redox properties. Ever-increasing environmental considerations make the processing of polyanilines shift from toxic organic solvent-based system to eco-friendly water-based system. The present paper reviews the synthesis of water-borne conducting polyanilines, and possible applications are discussed including supercapacitor electrode material, metal free corrosion protection coating, lithium oxygen battery cathode material and ultraviolet curable resin.
Among the intrinsically conductive polymers, polyanilines have been of great interest in the past decades due to their wide applications in many fields, thanks to their reasonably good conductivity, easy preparation, and special redox properties. Ever-increasing environmental considerations make the processing of polyanilines shift from toxic organic solvent-based system to eco-friendly water-based system. The present paper reviews the synthesis of water-borne conducting polyanilines, and possible applications are discussed including supercapacitor electrode material, metal free corrosion protection coating, lithium oxygen battery cathode material and ultraviolet curable resin.
2013, 31(6): 870-878
doi: 10.1007/s10118-013-1268-x
Abstract:
The miscibility of poly(vinyl chloride)/poly(n-butyl methacrylate) (PVC/PnBMA) blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry (DSC) and atomic force microscopy (AFM), respectively. This blend exhibited a lower critical solution temperature behavior. Below 120℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.
The miscibility of poly(vinyl chloride)/poly(n-butyl methacrylate) (PVC/PnBMA) blend and the interdiffusion kinetics of PVC/PnBMA laminates have been investigated by differential scanning calorimetry (DSC) and atomic force microscopy (AFM), respectively. This blend exhibited a lower critical solution temperature behavior. Below 120℃, DSC results showed each blend with different PVC contents exhibited only a single glass transition temperature which increased with PVC content, indicating that PVC and PnBMA were miscible. After PVC/PnBMA laminates were annealed at different temperature for different time, a smooth cross-section across interface was prepared by ultramicrotoming. Combined with topography and phase images of tapping mode AFM, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. In a regime of rubbery/rubbery interdiffusion, the diffusion obeyed a typical Fickian Case-I behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was in good agreement with that obtained from DSC and positron annihilation lifetime spectroscopy. However, in the regime of glassy/rubbery interdiffusion, the diffusion followed a typical Case-II behavior where the interface width was proportional to annealing time. These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.
2013, 31(6): 879-884
doi: 10.1007/s10118-013-1274-z
Abstract:
Improved hybrid solar cells consisting of vertical aligned cadmium sulfide (CdS) nanorod arrays and interpenetrating polythiophene (P3HT) have been achieved via modification of CdS nanorod surface by using conjugated N719 dye. The complete infiltration of P3HT between CdS nanorods interspacing was verified by scanning electron microscopy. By employing absorption and photoluminescence spectra, and current-voltage characterization the interaction between N719 molecules and CdS nanorods/P3HT interface was explored, and the role of N719 dye on the improvement of device performance was discussed.
Improved hybrid solar cells consisting of vertical aligned cadmium sulfide (CdS) nanorod arrays and interpenetrating polythiophene (P3HT) have been achieved via modification of CdS nanorod surface by using conjugated N719 dye. The complete infiltration of P3HT between CdS nanorods interspacing was verified by scanning electron microscopy. By employing absorption and photoluminescence spectra, and current-voltage characterization the interaction between N719 molecules and CdS nanorods/P3HT interface was explored, and the role of N719 dye on the improvement of device performance was discussed.
2013, 31(6): 885-893
doi: 10.1007/s10118-013-1282-z
Abstract:
Vanadium(III) complexes bearing thiophenol-phosphine ligands (2a-2b) (2-R-6-PPh2-C6H2S) VCl2(THF)2 (2a: R=H; 2b: R=Me3Si) were prepared from VCl3(THF)3 by treating with 1.0 equiv of the ligand in tetrahydrofuran in the presence of excess triethylamine. The two complexes were characterized by FTIR and mass spectra as well as elemental analyses. On activation with Et2AlCl, these complexes exhibited high catalytic activities (up to 22.1 kg PE/(mmolVhbar)) even at high temperature (70℃), and produced high molecular weight polymers with unimodal molecular weight distributions, indicating the polymerization took place in a single-site nature. This result may be attributed to benefits of introduction of second-row donor atoms for adjusting charge density of the vanadium centers. In addition, these complexes also exhibited high catalytic activities for ethylene/1-hexene copolymerization. Catalytic activity, comonomer incorporation and polymer molecular weight can be controlled in a wide range by the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration and polymerization reaction temperature.
Vanadium(III) complexes bearing thiophenol-phosphine ligands (2a-2b) (2-R-6-PPh2-C6H2S) VCl2(THF)2 (2a: R=H; 2b: R=Me3Si) were prepared from VCl3(THF)3 by treating with 1.0 equiv of the ligand in tetrahydrofuran in the presence of excess triethylamine. The two complexes were characterized by FTIR and mass spectra as well as elemental analyses. On activation with Et2AlCl, these complexes exhibited high catalytic activities (up to 22.1 kg PE/(mmolVhbar)) even at high temperature (70℃), and produced high molecular weight polymers with unimodal molecular weight distributions, indicating the polymerization took place in a single-site nature. This result may be attributed to benefits of introduction of second-row donor atoms for adjusting charge density of the vanadium centers. In addition, these complexes also exhibited high catalytic activities for ethylene/1-hexene copolymerization. Catalytic activity, comonomer incorporation and polymer molecular weight can be controlled in a wide range by the variation of catalyst structure and the reaction parameters such as Al/V molar ratio, comonomer feed concentration and polymerization reaction temperature.
2013, 31(6): 894-900
doi: 10.1007/s10118-013-1277-9
Abstract:
A new macromolecular surface modifier, a copolymer of lauryl methacrylate (LMA) and poly(ethylene glycol) methyl methacrylate (PEGMA), was synthesized through free radical polymerization. The copolymer was characterized by nuclear magnetic resonance spectrum (1H-NMR) and thermogravimetric analysis (TGA). The copolymer was used to blend with polyethylene. The binary blends have been characterized by attenuated total reflection/Fourier transform infrared (ATR-FTIR), contact-angle measurements (CDA) and scanning electron microscopy (SEM). The results indicated that poly(ethylene glycol) methyl methacrylate-co-lauryl methacrylate (PEGMA-co-LMA) could diffuse preferably onto the surface of the polyethylene (PE) film, and thus can be used as an efficient surface modifier for PE.
A new macromolecular surface modifier, a copolymer of lauryl methacrylate (LMA) and poly(ethylene glycol) methyl methacrylate (PEGMA), was synthesized through free radical polymerization. The copolymer was characterized by nuclear magnetic resonance spectrum (1H-NMR) and thermogravimetric analysis (TGA). The copolymer was used to blend with polyethylene. The binary blends have been characterized by attenuated total reflection/Fourier transform infrared (ATR-FTIR), contact-angle measurements (CDA) and scanning electron microscopy (SEM). The results indicated that poly(ethylene glycol) methyl methacrylate-co-lauryl methacrylate (PEGMA-co-LMA) could diffuse preferably onto the surface of the polyethylene (PE) film, and thus can be used as an efficient surface modifier for PE.
2013, 31(6): 901-911
doi: 10.1007/s10118-013-1275-y
Abstract:
6,7-Dialkoxy-2,3-diphenylquinoxaline based narrow band gap conjugated polymers, poly[2,7-(9-octyl-9H-carbazole)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PCDTQ) and poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PFDTQ), have been synthesized by Suzuki polycondensation. Their optical, electrochemical, transport and photovoltaic properties have been investigated in detail. Hole mobilities of PCDTQ and PFDTQ films spin coated from 1,2-dichlorobenzene (DCB) solutions are 1.0?10-4 and 4.1?10-4 cm2V-1s-1, respectively. Polymer solar cells were fabricated with the as-synthesized polymers as the donor and PC61BM and PC71BM as the acceptor. Devices based on PCDTQ:PC71BM (1:3) and PFDTQ:PC71BM (1:3) fabricated from DCB solutions demonstrated a power conversion efficiency (PCE) of 2.5% with a Voc of 0.95 V and a PCE of 2.5% with a Voc of 0.98 V, respectively, indicating they are promising donor materials.
6,7-Dialkoxy-2,3-diphenylquinoxaline based narrow band gap conjugated polymers, poly[2,7-(9-octyl-9H-carbazole)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PCDTQ) and poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thinenyl-(6,7-dialkoxy-2,3-diphenylquinoxaline))] (PFDTQ), have been synthesized by Suzuki polycondensation. Their optical, electrochemical, transport and photovoltaic properties have been investigated in detail. Hole mobilities of PCDTQ and PFDTQ films spin coated from 1,2-dichlorobenzene (DCB) solutions are 1.0?10-4 and 4.1?10-4 cm2V-1s-1, respectively. Polymer solar cells were fabricated with the as-synthesized polymers as the donor and PC61BM and PC71BM as the acceptor. Devices based on PCDTQ:PC71BM (1:3) and PFDTQ:PC71BM (1:3) fabricated from DCB solutions demonstrated a power conversion efficiency (PCE) of 2.5% with a Voc of 0.95 V and a PCE of 2.5% with a Voc of 0.98 V, respectively, indicating they are promising donor materials.
2013, 31(6): 912-923
doi: 10.1007/s10118-013-1288-6
Abstract:
To further enhance the transfection efficiency of a micelleplex system based on monomethoxy poly(ethylene glycol)-block-poly(-caprolactone)-block-poly(L-lysine) (MPEG-b-PCL-b-PLL), cholesterol (Chol) moieties are attached to the -termini of PLL segments to obtain MPEG-b-PCL-b-PLL/Chol. The structure and morphology of the copolymer are studied by 1H-NMR, TEM and DLS (dynamic light scattering). The cytotoxicity, cell uptake, endosomal release and mRNA knockdown are studied by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, flow cytometry, CLSM (confocal laser scanning microscopy) and RT-PCR (real-time polymerase chain reaction). The results show that compared to their precursor MPEG-b-PCL-b-PLL, the cholesterol-grafted copolymer shows significantly lower toxicity, more rapid cellular endocytosis and endosome escape, and consequently displays enhanced siRNA transfection efficiency even at a lower N/P ratio. These improvements are ascribed to enhanced interaction of the cholesterol moieties with both cellular membrane and endosomal membrane. Moreover, effect of the PLL block length is examined. The final conclusion is that long enough PLL segments and incorporation of proper fraction of cholesterol onto the PLL segments benefit the enhancement of siRNA transfection efficiency.
To further enhance the transfection efficiency of a micelleplex system based on monomethoxy poly(ethylene glycol)-block-poly(-caprolactone)-block-poly(L-lysine) (MPEG-b-PCL-b-PLL), cholesterol (Chol) moieties are attached to the -termini of PLL segments to obtain MPEG-b-PCL-b-PLL/Chol. The structure and morphology of the copolymer are studied by 1H-NMR, TEM and DLS (dynamic light scattering). The cytotoxicity, cell uptake, endosomal release and mRNA knockdown are studied by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay, flow cytometry, CLSM (confocal laser scanning microscopy) and RT-PCR (real-time polymerase chain reaction). The results show that compared to their precursor MPEG-b-PCL-b-PLL, the cholesterol-grafted copolymer shows significantly lower toxicity, more rapid cellular endocytosis and endosome escape, and consequently displays enhanced siRNA transfection efficiency even at a lower N/P ratio. These improvements are ascribed to enhanced interaction of the cholesterol moieties with both cellular membrane and endosomal membrane. Moreover, effect of the PLL block length is examined. The final conclusion is that long enough PLL segments and incorporation of proper fraction of cholesterol onto the PLL segments benefit the enhancement of siRNA transfection efficiency.
2013, 31(6): 924-937
doi: 10.1007/s10118-013-1281-0
Abstract:
We report on the fabrication of self-assembled micelles from ABC-type miktoarm star polypeptide hybrid copolymers consisting of poly(ethylene oxide), poly(L-lysine), and poly(e-caprolactone) arms, PEO(-b-PLL)-b-PCL, and their functional applications as co-delivery nanocarriers of chemotherapeutic drugs and plasmid DNA. Miktoarm star copolymer precursors, PEO(-b-PZLL)-b-PCL, were synthesized at first via the combination of consecutive click reactions and ring-opening polymerizations (ROP), where PZLL is poly(-benzyloxycarbonyl-L-lysine). Subsequently, the deprotection of PZLL arm afforded amphiphilic miktoarm star copolymers, PEO(-b-PLL)-b-PCL. In aqueous media at pH 7.4, PEO(-b-PLL)-b-PCL self-assembles into micelles consisting of PCL cores and hydrophilic PEO/PLL hybrid coronas. The hydrophobic micellar cores can effectively encapsulate model hydrophobic anticancer drug, paclitaxel; whereas positively charged PLL arms within mixed micellar corona are capable of forming electrostatic polyplexes with negatively charged plasmid DNA (pDNA) at N/P ratios higher than ca. 2. Thus, PEO(-b-PLL)-b-PCL micelles can act as co-delivery nanovehicles for both chemotherapeutic drugs and genes. Furthermore, polyplexes of pDNA with paclitaxel-loaded PEO(-b-PLL)-b-PCL micelles exhibited improved transfection efficiency compared to that of pDNA/blank micelles. We expect that the reported strategy of varying chain topologies for the fabrication of co-delivery polymeric nanocarriers can be further applied to integrate with other advantageous functions such as targeting, imaging, and diagnostics.
We report on the fabrication of self-assembled micelles from ABC-type miktoarm star polypeptide hybrid copolymers consisting of poly(ethylene oxide), poly(L-lysine), and poly(e-caprolactone) arms, PEO(-b-PLL)-b-PCL, and their functional applications as co-delivery nanocarriers of chemotherapeutic drugs and plasmid DNA. Miktoarm star copolymer precursors, PEO(-b-PZLL)-b-PCL, were synthesized at first via the combination of consecutive click reactions and ring-opening polymerizations (ROP), where PZLL is poly(-benzyloxycarbonyl-L-lysine). Subsequently, the deprotection of PZLL arm afforded amphiphilic miktoarm star copolymers, PEO(-b-PLL)-b-PCL. In aqueous media at pH 7.4, PEO(-b-PLL)-b-PCL self-assembles into micelles consisting of PCL cores and hydrophilic PEO/PLL hybrid coronas. The hydrophobic micellar cores can effectively encapsulate model hydrophobic anticancer drug, paclitaxel; whereas positively charged PLL arms within mixed micellar corona are capable of forming electrostatic polyplexes with negatively charged plasmid DNA (pDNA) at N/P ratios higher than ca. 2. Thus, PEO(-b-PLL)-b-PCL micelles can act as co-delivery nanovehicles for both chemotherapeutic drugs and genes. Furthermore, polyplexes of pDNA with paclitaxel-loaded PEO(-b-PLL)-b-PCL micelles exhibited improved transfection efficiency compared to that of pDNA/blank micelles. We expect that the reported strategy of varying chain topologies for the fabrication of co-delivery polymeric nanocarriers can be further applied to integrate with other advantageous functions such as targeting, imaging, and diagnostics.
2013, 31(6): 938-945
doi: 10.1007/s10118-013-1286-8
Abstract:
Star-shaped oligothiophenes with hexakis(fluoren-2-yl)benzene (HFB) as cores were designed and synthesized. Grafting thiophene units to HFB results in a bond flattening of the core, and makes the molecules a flipping-twist shape. Their thermal, photophysical and electrochemical properties were studied. Highly cross-linked conjugated polymers can be produced by electropolymerization of T1-T3.
Star-shaped oligothiophenes with hexakis(fluoren-2-yl)benzene (HFB) as cores were designed and synthesized. Grafting thiophene units to HFB results in a bond flattening of the core, and makes the molecules a flipping-twist shape. Their thermal, photophysical and electrochemical properties were studied. Highly cross-linked conjugated polymers can be produced by electropolymerization of T1-T3.
2013, 31(6): 946-958
doi: 10.1007/s10118-013-1285-9
Abstract:
Crystal orientation and melting behavior of poly(-caprolactone) in a diblock copolymer of poly(-caprolactone)-block-poly(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PCL-b-PMPCS) was investigated. The degrees of polymerization of the PCL and PMPCS block are 200 and 98, respectively. With the PMPCS in a columnar liquid crystalline phase, the diblock is rod-coil one, which exhibits a lamellar phase morphology with the PCL layer thickness of 15.2 nm. Since the glass transition temperature of PMPCS block is much higher than the melting temperature of PCL, the crystallization of PCL is in a one-dimensionally hard confinement environment. Mainly on the basis of two-dimensional wide-angle X-ray diffraction experiments, we identified the orientation of PCL isothermally crystallized at various crystallization temperatures (Tcs). At high Tcs (Tc 10℃), the c-axis of the PCL crystal is along the layer normal of the microphase-separated sturcture. Decreasing Tc can result in the tilting of PCL c-axis with respect to the layer normal. The lower the Tc is, the more the c-axis inclines. Meanwhile, the b-axis of PCL remains perpendicular to the layer normal. At a very low Tc of -78℃, the orientation of the PCL crystals is completely random. For the samples isothermally crystallized at Tc 10℃, double melting behavior can be observed. While the low temperature endotherm reflects the melting of the crystals originally formed at the Tc applied, the high temperature one is associated with the crystals subjected to the process of recrystallization/reorganization upon heating due to the annealing effect.
Crystal orientation and melting behavior of poly(-caprolactone) in a diblock copolymer of poly(-caprolactone)-block-poly(2,5-bis[4-methoxyphenyl]oxycarbonyl)styrene) (PCL-b-PMPCS) was investigated. The degrees of polymerization of the PCL and PMPCS block are 200 and 98, respectively. With the PMPCS in a columnar liquid crystalline phase, the diblock is rod-coil one, which exhibits a lamellar phase morphology with the PCL layer thickness of 15.2 nm. Since the glass transition temperature of PMPCS block is much higher than the melting temperature of PCL, the crystallization of PCL is in a one-dimensionally hard confinement environment. Mainly on the basis of two-dimensional wide-angle X-ray diffraction experiments, we identified the orientation of PCL isothermally crystallized at various crystallization temperatures (Tcs). At high Tcs (Tc 10℃), the c-axis of the PCL crystal is along the layer normal of the microphase-separated sturcture. Decreasing Tc can result in the tilting of PCL c-axis with respect to the layer normal. The lower the Tc is, the more the c-axis inclines. Meanwhile, the b-axis of PCL remains perpendicular to the layer normal. At a very low Tc of -78℃, the orientation of the PCL crystals is completely random. For the samples isothermally crystallized at Tc 10℃, double melting behavior can be observed. While the low temperature endotherm reflects the melting of the crystals originally formed at the Tc applied, the high temperature one is associated with the crystals subjected to the process of recrystallization/reorganization upon heating due to the annealing effect.
