Login In
2016 Volume 34 Issue 3
2016, 34(3): 253-267
doi: 10.1007/s10118-016-1752-1
Abstract:
Structurally diverse bispropargyl ethers using resorcinol, quinol, 4,4'-dihydroxy biphenyl, bisphenol-A, 4,4'-dihydroxy diphenyl ketone, 4,4'-dihydroxy diphenylsulphone, trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were prepared by using phase transfer catalyst. Synthesized materials were separately blended with 4,4'-bismaleimido diphenyl methane (BMIM) in mole ratios (0.5:0.5). The materials were thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared (FTIR) spectrophotometer and thermogravimetric analyzer (TGA). Among the different materials investigated polyMRPE, polyMBPEBPA and polyMSPE show higher onset degradation temperature of 300 ℃ indicating higher thermal stability. The degradation kinetics is investigated using Flynn-Wall-Ozawa (FWO), Vyazovkin (VYZ) and Friedman (FRD) methods. Amongst the various cured materials investigated, the activation energy (Ea-D) values obtained for polyMRPE and polyMKPE were observed to increase continuously from a = 0.2 to 0.8 and the values range from 199 kJ/mol to 245 kJ/mol and 153 kJ/mol to 295 kJ/mol respectively. The crosslinked materials resulting from these bispropargyl monomers definitely need more energy for bond cleavage due to the presence of more aromatic units. The volatile products obtained during the thermal degradation of the polymers were analyzed using thermogravimetric-Fourier transform infrared analyses (TG-FTIR). The phenols, substituted phenols, carbon monoxide, carbon dioxide and small amount of aniline were found to be the major products during thermal degradation of these cured blends.
Structurally diverse bispropargyl ethers using resorcinol, quinol, 4,4'-dihydroxy biphenyl, bisphenol-A, 4,4'-dihydroxy diphenyl ketone, 4,4'-dihydroxy diphenylsulphone, trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were prepared by using phase transfer catalyst. Synthesized materials were separately blended with 4,4'-bismaleimido diphenyl methane (BMIM) in mole ratios (0.5:0.5). The materials were thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared (FTIR) spectrophotometer and thermogravimetric analyzer (TGA). Among the different materials investigated polyMRPE, polyMBPEBPA and polyMSPE show higher onset degradation temperature of 300 ℃ indicating higher thermal stability. The degradation kinetics is investigated using Flynn-Wall-Ozawa (FWO), Vyazovkin (VYZ) and Friedman (FRD) methods. Amongst the various cured materials investigated, the activation energy (Ea-D) values obtained for polyMRPE and polyMKPE were observed to increase continuously from a = 0.2 to 0.8 and the values range from 199 kJ/mol to 245 kJ/mol and 153 kJ/mol to 295 kJ/mol respectively. The crosslinked materials resulting from these bispropargyl monomers definitely need more energy for bond cleavage due to the presence of more aromatic units. The volatile products obtained during the thermal degradation of the polymers were analyzed using thermogravimetric-Fourier transform infrared analyses (TG-FTIR). The phenols, substituted phenols, carbon monoxide, carbon dioxide and small amount of aniline were found to be the major products during thermal degradation of these cured blends.
2016, 34(3): 268-279
doi: 10.1007/s10118-016-1751-2
Abstract:
The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler-Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl2-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21.
The penta-ether compound was synthesized by the reaction of di(trimethylolpropane) with sodium hydride as the strong base and methyl iodide as the alkyl halide. This compound was characterized by NMR, FTIR, and GC techniques. The MgCl2-supported titanium catalysts were incorporated with varying amounts of penta-ether compound as the internal donor and also the catalysts without the internal donor were synthesized. The synthesized catalysts and the conventional Ziegler-Natta catalyst were characterized. The titanium contents were determined by spectrophotometry, magnesium by complexometric titration and chloride by argentometric titration. The effects of the new internal donor on propylene polymerization with the prepared MgCl2-supported Ziegler-Natta catalysts were investigated and then these results were compared to the results obtained using the conventional diisobutyl phthalate-besed-Ziegler-Natta catalyst. The highest crystallinity degree, melting temperature, and isotacticity of polypropylene were obtained using the catalyst with a penta-ether/Mg molar ratio equal to 0.21.
2016, 34(3): 280-287
doi: 10.1007/s10118-016-1757-9
Abstract:
New pH-responsive saccharide hydrogels were designed and prepared using curdlan derivatives (curdlan-Boc-histidine, CUR-HIS). The CUR-HIS hydrogels possessed highly porous structures. The swelling ratios of CUR-HIS hydrogels increased with the degree of substitution of Boc-histidine groups. And the addition of 0.5 mol/L NaCl provoked a sharp reduction of swelling ratio of CUR-HIS hydrogels. Bovine serum albumin (BSA) can be efficiently encapsulated into CUR-HIS hydrogels. Moreover, the release profiles of BSA at different pH values from CUR-HIS hydrogels were significantly different. These hydrogels showed good biocompatibility in the cytotoxicity assays. The CUR-HIS hydrogels are of great potential in biomedical applications such as protein delivery systems.
New pH-responsive saccharide hydrogels were designed and prepared using curdlan derivatives (curdlan-Boc-histidine, CUR-HIS). The CUR-HIS hydrogels possessed highly porous structures. The swelling ratios of CUR-HIS hydrogels increased with the degree of substitution of Boc-histidine groups. And the addition of 0.5 mol/L NaCl provoked a sharp reduction of swelling ratio of CUR-HIS hydrogels. Bovine serum albumin (BSA) can be efficiently encapsulated into CUR-HIS hydrogels. Moreover, the release profiles of BSA at different pH values from CUR-HIS hydrogels were significantly different. These hydrogels showed good biocompatibility in the cytotoxicity assays. The CUR-HIS hydrogels are of great potential in biomedical applications such as protein delivery systems.
2016, 34(3): 288-297
doi: 10.1007/s10118-016-1754-z
Abstract:
In the present investigation, novel poly(amid-imide)/zinc oxide nanocomposites (PAI/ZnO NCs) containing benzoxazole and benzimidazole pendent groups with different amounts of modified zinc oxide nanoparticles (ZnO NPs) were successfully prepared via the ex situ method. Poly(amid-imide) (PAI) was prepared by direct polycondensation of 2-[3,5-bis(N-trimellitimidoyl)phenyl]benzoxazole (DCA) with 5-(2-benzimidazole)-1,3-phenylenediamine (DAMI) and provided the polymeric matrix with well-designed groups. The surface of ZnO NPs was functionalized with 3-aminopropyltriethoxysilane (APS) coupling agent to have a better dispersion and enhancing possible interactions of NPs with functional groups of polymer matrix. The amount of APS bonded to the ZnO surface was determined by thermogravimetric analysis. PAI/ZnO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM analysis showed that the modified ZnO nanoparticles were homogeneously dispersed in polymer matrix. In addition, TGA data indicated an enhancement of thermal stability of the nanocomposite compared with the neat polymer.
In the present investigation, novel poly(amid-imide)/zinc oxide nanocomposites (PAI/ZnO NCs) containing benzoxazole and benzimidazole pendent groups with different amounts of modified zinc oxide nanoparticles (ZnO NPs) were successfully prepared via the ex situ method. Poly(amid-imide) (PAI) was prepared by direct polycondensation of 2-[3,5-bis(N-trimellitimidoyl)phenyl]benzoxazole (DCA) with 5-(2-benzimidazole)-1,3-phenylenediamine (DAMI) and provided the polymeric matrix with well-designed groups. The surface of ZnO NPs was functionalized with 3-aminopropyltriethoxysilane (APS) coupling agent to have a better dispersion and enhancing possible interactions of NPs with functional groups of polymer matrix. The amount of APS bonded to the ZnO surface was determined by thermogravimetric analysis. PAI/ZnO nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). SEM analysis showed that the modified ZnO nanoparticles were homogeneously dispersed in polymer matrix. In addition, TGA data indicated an enhancement of thermal stability of the nanocomposite compared with the neat polymer.
2016, 34(3): 298-306
doi: 10.1007/s10118-016-1737-0
Abstract:
Tandem catalytic systems, consisting of ethylene bis(indenyl) zirconium dichloride with two different cocatalysts, alkylaluminum (diethylaluminium chloride or trialkylaluminum) and methylaluminoxane, were employed in preparing branched polyethylene from ethylene as sole monomer. The catalytic system rac-Et(Ind)2ZrCl2/AlEt2Cl/MAO exhibited high incorporation (29.0/1000C). The oligomerization and copolymerization reaction conditions in the tandem catalytic system, as well as the different cocatalysts, have effects on the catalytic activity and the properties of the obtained polymer, such as melting temperature, crystallinity, molecular weight and molecular weight distribution. Moreover, the oligomerization reaction condition is the main factor in altering the properties and structures of polyethylene.
Tandem catalytic systems, consisting of ethylene bis(indenyl) zirconium dichloride with two different cocatalysts, alkylaluminum (diethylaluminium chloride or trialkylaluminum) and methylaluminoxane, were employed in preparing branched polyethylene from ethylene as sole monomer. The catalytic system rac-Et(Ind)2ZrCl2/AlEt2Cl/MAO exhibited high incorporation (29.0/1000C). The oligomerization and copolymerization reaction conditions in the tandem catalytic system, as well as the different cocatalysts, have effects on the catalytic activity and the properties of the obtained polymer, such as melting temperature, crystallinity, molecular weight and molecular weight distribution. Moreover, the oligomerization reaction condition is the main factor in altering the properties and structures of polyethylene.
2016, 34(3): 307-315
doi: 10.1007/s10118-016-1755-y
Abstract:
Aromatic amphiphilic molecules (1) consisting of three biphenyl groups linked together with ether bonds as a rigid rod segment and poly(ethylene oxide) with the number of repeating units of 17 as a coil segment were synthesized, and their self-assembly behavior in the bulk state and aqueous solution was investigated. In bulk, molecules 1 self-assembled into 1-D lamellar structure in the solid state or smectic A phase in the liquid crystalline phase via the cooperative effects of - stacking, micro-phase separation and hydrogen bond interactions. In dilute aqueous solutions, molecules 1 were observed to self-assemble into cylindrical micelles owned uniform diameter and length of hundreds of nanometers.
Aromatic amphiphilic molecules (1) consisting of three biphenyl groups linked together with ether bonds as a rigid rod segment and poly(ethylene oxide) with the number of repeating units of 17 as a coil segment were synthesized, and their self-assembly behavior in the bulk state and aqueous solution was investigated. In bulk, molecules 1 self-assembled into 1-D lamellar structure in the solid state or smectic A phase in the liquid crystalline phase via the cooperative effects of - stacking, micro-phase separation and hydrogen bond interactions. In dilute aqueous solutions, molecules 1 were observed to self-assemble into cylindrical micelles owned uniform diameter and length of hundreds of nanometers.
2016, 34(3): 316-323
doi: 10.1007/s10118-016-1756-x
Abstract:
For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of pH-sensitive poly(ethylene glycol)-poly (-benzyl-L-glutamate-co-glutamic acid) (PEG-PGA(65), 65 denotes the molar ratio of glutamic acid in poly(-benzyl-L-glutamate-co-glutamic acid)). PEG-PGA(65) showed low cytotoxicity and could shield the positive charge of DNA/PEI (1:1) polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in HeLa cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at pH of 7.4. However, the transfection efficiency recovered a lot by culturing at pH of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at pH 6.0, because of the pH triggered deshielding action of PEG-PGA(65). Due to the good biocompatibility and suitable pH triggered shielding/deshielding property, PEG-PGA(65) could be a potential shielding system for polycationic gene carriers used in vivo.
For the purpose of increasing the in vivo stability of polycation gene carriers, we prepared a kind of pH-sensitive poly(ethylene glycol)-poly (-benzyl-L-glutamate-co-glutamic acid) (PEG-PGA(65), 65 denotes the molar ratio of glutamic acid in poly(-benzyl-L-glutamate-co-glutamic acid)). PEG-PGA(65) showed low cytotoxicity and could shield the positive charge of DNA/PEI (1:1) polyplexes efficiently. The transfection was enhanced due to the partially charge shielding in HeLa cell line at pH of 7.4. There was almost no transfection efficiency when the surface charge of the ternary particles turned to negative at pH of 7.4. However, the transfection efficiency recovered a lot by culturing at pH of 6.0 at the beginning of transfection. Confocal microscopic observation and flow cytometry results showed DNA/PEI polyplexes should be efficiently released and endocytosized at pH 6.0, because of the pH triggered deshielding action of PEG-PGA(65). Due to the good biocompatibility and suitable pH triggered shielding/deshielding property, PEG-PGA(65) could be a potential shielding system for polycationic gene carriers used in vivo.
2016, 34(3): 324-331
doi: 10.1007/s10118-016-1760-1
Abstract:
A novel conjugated polymer, poly(1), containing thiourea moieties in main chain is synthesized via Suzuki coupling reaction. The addition of cuprous ion quenches the fluorescence of poly(1), whereas the fluorescence changes slightly upon addition of other metal ions, exhibiting the fluorescent almost turn-off sensing ability towards Cu+. When hydrogen peroxide was added to the solution containing poly(1) and Cu+, Cu+ was oxidized into Cu2+, resulting in the fluorescence recovery. The H2O2 released from glucose oxidation by glucose oxidase (GOD) also recovered the fluorescence of poly(1)/Cu+ solution. The results indicated that the poly(1)/Cu+ solution could serve as a sensing platform for hydrogen peroxide and glucose.
A novel conjugated polymer, poly(1), containing thiourea moieties in main chain is synthesized via Suzuki coupling reaction. The addition of cuprous ion quenches the fluorescence of poly(1), whereas the fluorescence changes slightly upon addition of other metal ions, exhibiting the fluorescent almost turn-off sensing ability towards Cu+. When hydrogen peroxide was added to the solution containing poly(1) and Cu+, Cu+ was oxidized into Cu2+, resulting in the fluorescence recovery. The H2O2 released from glucose oxidation by glucose oxidase (GOD) also recovered the fluorescence of poly(1)/Cu+ solution. The results indicated that the poly(1)/Cu+ solution could serve as a sensing platform for hydrogen peroxide and glucose.
2016, 34(3): 332-343
doi: 10.1007/s10118-016-1750-3
Abstract:
Composite polymer electrolytes (CPEs) comprising poly(vinilydene fluoride-hexafluoro propylene), PVDF-co-HFP and zinc triflate, Zn(CF3SO3)2 with varying concentrations of ZrO2 nanofillers were prepared by solution casting technique with N,N-dimethyl formamide (DMF) as the common solvent. The polymer electrolyte specimen with the particular composition 75 wt% PVDF-co-HFP: 25 wt% ZnTf + 7 wt% ZrO2 showed the highest conductivity of 4.6 10-4 S/cm at 298 K as confirmed from impedance measurements and favored by the rich amorphous phase of the CPE revealed from room temperature X-ray diffraction analysis (XRD). The electrical conductivity relaxation time and its distribution within the materials have been evaluated from the electric modulus M and impedance Z data which showed the occurrence of non-Debye type of relaxation phenomenon. The changes in the surface morphology of the CPEs were examined using scanning electron microscopy (SEM). The electrochemical stability window of CPE is found to be 2.6 V with a thermal stability up to 300 ℃. An electrochemical cell has been fabricated based on Zn/MnO2 electrode couple under a constant load of 1 M and its discharge characteristics have been evaluated.
Composite polymer electrolytes (CPEs) comprising poly(vinilydene fluoride-hexafluoro propylene), PVDF-co-HFP and zinc triflate, Zn(CF3SO3)2 with varying concentrations of ZrO2 nanofillers were prepared by solution casting technique with N,N-dimethyl formamide (DMF) as the common solvent. The polymer electrolyte specimen with the particular composition 75 wt% PVDF-co-HFP: 25 wt% ZnTf + 7 wt% ZrO2 showed the highest conductivity of 4.6 10-4 S/cm at 298 K as confirmed from impedance measurements and favored by the rich amorphous phase of the CPE revealed from room temperature X-ray diffraction analysis (XRD). The electrical conductivity relaxation time and its distribution within the materials have been evaluated from the electric modulus M and impedance Z data which showed the occurrence of non-Debye type of relaxation phenomenon. The changes in the surface morphology of the CPEs were examined using scanning electron microscopy (SEM). The electrochemical stability window of CPE is found to be 2.6 V with a thermal stability up to 300 ℃. An electrochemical cell has been fabricated based on Zn/MnO2 electrode couple under a constant load of 1 M and its discharge characteristics have been evaluated.
2016, 34(3): 344-358
doi: 10.1007/s10118-016-1745-0
Abstract:
The introduction of concept of the three domains of isotactic polypropylene (iPP) by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of iPP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the nuclei at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the nuclei at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains.
The introduction of concept of the three domains of isotactic polypropylene (iPP) by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of iPP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the nuclei at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the nuclei at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains.
2016, 34(3): 359-366
doi: 10.1007/s10118-016-1746-z
Abstract:
Synthesis of telechelic trans-1,4-polyisoprenes (TPI: trans-structure 95%) was evaluated based on two different methods of oxidative cleavage (indirect cleavage: first epoxidation of TPI, then the selective cleavage of epoxidized units in epoxidized trans-1,4-polyisoprene (ETPI) and direct cleavage of isoprene units in TPI). The influence of solvents and the ratio of oxidative agents was investigated by 1H-NMR and 13C-NMR. A series of well-defined telechelic TPI with double terminated functional groups and less side reaction (molecular weight distribution range: 1.96-2.26) were synthesized by indirect cleavage in chloroform. Telechelic TPI showed similar crystallization behavior with TPI and interesting cold crystallization behavior characterized by DSC.
Synthesis of telechelic trans-1,4-polyisoprenes (TPI: trans-structure 95%) was evaluated based on two different methods of oxidative cleavage (indirect cleavage: first epoxidation of TPI, then the selective cleavage of epoxidized units in epoxidized trans-1,4-polyisoprene (ETPI) and direct cleavage of isoprene units in TPI). The influence of solvents and the ratio of oxidative agents was investigated by 1H-NMR and 13C-NMR. A series of well-defined telechelic TPI with double terminated functional groups and less side reaction (molecular weight distribution range: 1.96-2.26) were synthesized by indirect cleavage in chloroform. Telechelic TPI showed similar crystallization behavior with TPI and interesting cold crystallization behavior characterized by DSC.
2016, 34(3): 367-377
doi: 10.1007/s10118-016-1748-x
Abstract:
In this work, we describe a straightforward approach to produce monodisperse Janus and core-shell particles by using organic solvent free single emulsion droplet-based microfluidic device combining with off-chip polymerization. To accomplish this, methyl methacrylate (MMA) was used as both the oil phase and solvent to dissolve a polymerizable PEG-based macromolecular surfactant, instead of traditional surfactant, and the photo-initiator. Janus particles can be easily obtained by off-chip UV polymerization due to polymerization induced phase separation between PEG and the formed poly(methyl methacrylate). At the same time, core-shell particles can also be easily attained by inverting the original collecting tube several times and then exposing to UV light. These results may extend the scope of microfluidic technology and the studies on polymerization induced self-assembly/phase-separation into easy fabrication of various new functional materials.
In this work, we describe a straightforward approach to produce monodisperse Janus and core-shell particles by using organic solvent free single emulsion droplet-based microfluidic device combining with off-chip polymerization. To accomplish this, methyl methacrylate (MMA) was used as both the oil phase and solvent to dissolve a polymerizable PEG-based macromolecular surfactant, instead of traditional surfactant, and the photo-initiator. Janus particles can be easily obtained by off-chip UV polymerization due to polymerization induced phase separation between PEG and the formed poly(methyl methacrylate). At the same time, core-shell particles can also be easily attained by inverting the original collecting tube several times and then exposing to UV light. These results may extend the scope of microfluidic technology and the studies on polymerization induced self-assembly/phase-separation into easy fabrication of various new functional materials.
2016, 34(3): 378-389
doi: 10.1007/s10118-016-1753-0
Abstract:
Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (exo-PTNP-b-exo-PCONBI) were synthesized by ring-opening metathesis polymerization. The endo- or exo-PTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNP-b-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant () of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photo-crosslinking, the polymer film has an increased of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ℃, and an enhanced decomposition temperature of 405 ℃, compared to those of polymer films without irradiation.
Block copolymers poly(endo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (endo-PTNP-b-exo-PCONBI) and poly(exo-N-3,5-bis(trifluoromethyl)biphenyl-norbornene-pyrrolidine)-block-poly(exo-N-(cinnamoyloxyethyl)-7-oxanorborn-5-ene-2,3-dicarboximide) (exo-PTNP-b-exo-PCONBI) were synthesized by ring-opening metathesis polymerization. The endo- or exo-PTNP served as the high dielectric functional chain, and exo-PCONBI acted as the crosslinking segment. The endo-PTNP-b-exo-PCONBI, in which endo-PTNP has a high content of trans double bond and adopts isotactic configuration, shows a dielectric constant () of 15.5, whereas exo-PTNP-b-exo-PCONBI, in which exo-PTNP has 67% trans double bonds and atactic microstructure, displays relatively low of 7.1. The cinnamate groups in exo-PCONBI were crosslinked to form three-dimensional network by cycloaddition reaction under UV irradiation. Exposed to UV-light for 10 min, the cinnamate group in polymer films has a crosslinking conversion of 36%, as determined by UV-Vis absorption measurements. By photo-crosslinking, the polymer film has an increased of 16.6, a dielectric loss of 0.03, an elevated glass-transition temperature of 137 ℃, and an enhanced decomposition temperature of 405 ℃, compared to those of polymer films without irradiation.
2016, 34(3): 390-398
doi: 10.1007/s10118-016-1768-6
Abstract:
The trichlorozirconium 2-hydrazonides (R=H, A; R=CH3, B) were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-(furan-2-ylmethylene)-2-phenylhydrazonide or 1-(furan-2-ylethylidene)-2-phenyl hydrazonide in the solvent tetrahydrofuran (THF), respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the 2-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.
The trichlorozirconium 2-hydrazonides (R=H, A; R=CH3, B) were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-(furan-2-ylmethylene)-2-phenylhydrazonide or 1-(furan-2-ylethylidene)-2-phenyl hydrazonide in the solvent tetrahydrofuran (THF), respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the 2-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.
