Login In
2009 Volume 27 Issue 5
2009, 27(5): 601-610
Abstract:
The persistence length and the overlap concentration (c*) of poly(ethylene oxide) (PEO) and hydroxyethylcellulose (HEC) with similar molecular weight in 1 × TBE buffer were studied by laser light scattering and viscometry. Their effect on DNA separation was investigated by capillary electrophoresis. It was determined that the persistence length of HEC was at least 5 times higher than that of PEO. Therefore, the c* of HEC was smaller than that of PEO by a factor of ca. 2.5. It was also found that the c* values determined by laser light scattering were much lower than those by viscometry. We attributed it to the state of polymer chains in which c* was measured: laser light scattering determined the c* in ultradilute solution where the polymer chains were in the static state; while viscometry determined the c* in dilute or semidilute concentration region with polymer chains being in the hydrodynamic flowing state. When used in DNA separation, polymer chains were in different states due to the disturbance of DNA molecules, making c* region dependent. When the real concentration was normalized by c*, PEO and HEC showed almost equal performance in separating ΦX174/Hae III DNA digest in dilute solution, even though their persistence lengths were quite different.
The persistence length and the overlap concentration (c*) of poly(ethylene oxide) (PEO) and hydroxyethylcellulose (HEC) with similar molecular weight in 1 × TBE buffer were studied by laser light scattering and viscometry. Their effect on DNA separation was investigated by capillary electrophoresis. It was determined that the persistence length of HEC was at least 5 times higher than that of PEO. Therefore, the c* of HEC was smaller than that of PEO by a factor of ca. 2.5. It was also found that the c* values determined by laser light scattering were much lower than those by viscometry. We attributed it to the state of polymer chains in which c* was measured: laser light scattering determined the c* in ultradilute solution where the polymer chains were in the static state; while viscometry determined the c* in dilute or semidilute concentration region with polymer chains being in the hydrodynamic flowing state. When used in DNA separation, polymer chains were in different states due to the disturbance of DNA molecules, making c* region dependent. When the real concentration was normalized by c*, PEO and HEC showed almost equal performance in separating ΦX174/Hae III DNA digest in dilute solution, even though their persistence lengths were quite different.
2009, 27(5): 611-619
Abstract:
A novel kind of hexa-armed fluorene-benzene copolymer based on a hexaazaisowurtzitane core was synthesized through Suzuki coupling polycondensation. The introduction of this bulky caged-core could not only enhance the photoluminescence quantum efficiency, but also improve the electroluminescence properties, especially suppress the common green-color emission of polyfluorenes (PFs) material during device operation. These features can be attributed to the successful suppression of PF’s chain aggregation which profits from the introduction of the bulky hexaazaisowurtzitane core and the design of multi-armed architecture.
A novel kind of hexa-armed fluorene-benzene copolymer based on a hexaazaisowurtzitane core was synthesized through Suzuki coupling polycondensation. The introduction of this bulky caged-core could not only enhance the photoluminescence quantum efficiency, but also improve the electroluminescence properties, especially suppress the common green-color emission of polyfluorenes (PFs) material during device operation. These features can be attributed to the successful suppression of PF’s chain aggregation which profits from the introduction of the bulky hexaazaisowurtzitane core and the design of multi-armed architecture.
2009, 27(5): 621-627
Abstract:
This study deals with polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membranes for propane separation from propane/nitrogen mixtures, which is relevant to the recovery of propane in petroleum and chemical industry. The surface and cross-section morphology of PDMS/PVDF composite membranes was observed by scanning electron microscope (SEM). The surface morphology of PDMS/PVDF composite membranes is very dense. There are three layers, the thin dense top layer, finger-like porous middle layer and sponge-like under layer in the cross-section SEM image of PDMS/PVDF composite membranes. The effects of the types of cross-linking agents and pressure on the membrane permselectivity were investigated. The permeability of nitrogen was independent of feed pressure. However, the permeability of propane increased with the pressure increasing for all membranes. The membrane cured by a tri-functional crosslinker with attached vinyl groups had better performance than the tetra-functional one, in both selectivity and permeation flux. The total permeation flux is 1.769× 10-2 cm3(STP)/(cm2·s) and the separation factor is 19.17 when the mole percent of propane in the gas mixture is 10 at the 0.2 MPa pressure difference and 25°C.
This study deals with polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membranes for propane separation from propane/nitrogen mixtures, which is relevant to the recovery of propane in petroleum and chemical industry. The surface and cross-section morphology of PDMS/PVDF composite membranes was observed by scanning electron microscope (SEM). The surface morphology of PDMS/PVDF composite membranes is very dense. There are three layers, the thin dense top layer, finger-like porous middle layer and sponge-like under layer in the cross-section SEM image of PDMS/PVDF composite membranes. The effects of the types of cross-linking agents and pressure on the membrane permselectivity were investigated. The permeability of nitrogen was independent of feed pressure. However, the permeability of propane increased with the pressure increasing for all membranes. The membrane cured by a tri-functional crosslinker with attached vinyl groups had better performance than the tetra-functional one, in both selectivity and permeation flux. The total permeation flux is 1.769× 10-2 cm3(STP)/(cm2·s) and the separation factor is 19.17 when the mole percent of propane in the gas mixture is 10 at the 0.2 MPa pressure difference and 25°C.
2009, 27(5): 629-637
Abstract:
Functionalized PS/SiO2 composite nanoparticles bearing sulfonic groups on the surface were successfully synthesized via emulsion copolymerization using a polymerizable emulsifier α olefin solfonate (AOS). As demonstrated by transmission electron microscopy and atomic force microscopy, well-defined core-shell PS/SiO2 composite nanoparticles with a diameter of 50 nm were obtained. Sulfonic groups introduced onto the surface of the composite nanoparticles were quantified by FTIR, and can be controlled to some extent via a two-stage procedure.
Functionalized PS/SiO2 composite nanoparticles bearing sulfonic groups on the surface were successfully synthesized via emulsion copolymerization using a polymerizable emulsifier α olefin solfonate (AOS). As demonstrated by transmission electron microscopy and atomic force microscopy, well-defined core-shell PS/SiO2 composite nanoparticles with a diameter of 50 nm were obtained. Sulfonic groups introduced onto the surface of the composite nanoparticles were quantified by FTIR, and can be controlled to some extent via a two-stage procedure.
2009, 27(5): 639-646
Abstract:
The work presents the synthesis and characterization of amidated pectin (AP) based polymer electrolyte membranes (PEM) crosslinked with glutaraldehyde (GA). The prepared membranes are characterized by Fourier transform infrared spectroscopy (FTIR), organic elemental analysis, X-ray diffraction studies (XRD), thermogravimetric analysis (TGA) and impedance spectroscopy. Mechanical properties of the membranes are evaluated by tensile tests. The degree of amidation (DA), molar and mass reaction yields (YM and YN) are calculated based on the results of organic elemental analysis. FTIR spectroscopy indicated the presence of primary and secondary amide absorption bands. XRD pattern of membranes clearly indicates that there is a considerable increase in crystallinity as compared to parent pectin. TGA studies indicate that AP is less thermally stable than reference pectin. A maximum room temperature conductivity of 1.098 ×10-3 Scm-1 is obtained in the membrane, which is designated as AP-3. These properties make them good candidates for low cost biopolymer electrolyte membranes for fuel cell applications.
The work presents the synthesis and characterization of amidated pectin (AP) based polymer electrolyte membranes (PEM) crosslinked with glutaraldehyde (GA). The prepared membranes are characterized by Fourier transform infrared spectroscopy (FTIR), organic elemental analysis, X-ray diffraction studies (XRD), thermogravimetric analysis (TGA) and impedance spectroscopy. Mechanical properties of the membranes are evaluated by tensile tests. The degree of amidation (DA), molar and mass reaction yields (YM and YN) are calculated based on the results of organic elemental analysis. FTIR spectroscopy indicated the presence of primary and secondary amide absorption bands. XRD pattern of membranes clearly indicates that there is a considerable increase in crystallinity as compared to parent pectin. TGA studies indicate that AP is less thermally stable than reference pectin. A maximum room temperature conductivity of 1.098 ×10-3 Scm-1 is obtained in the membrane, which is designated as AP-3. These properties make them good candidates for low cost biopolymer electrolyte membranes for fuel cell applications.
2009, 27(5): 647-658
Abstract:
The curing behavior of diglycidyl ether of bisphenol-A (DGEBA) with aromatic diamide-diimide-diamines having aryl ether, sulfone and methylene linkages was studied by differential scanning calorimetry (DSC). Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine (S) in a mixture of acetic acid and pyridine (3:2 V/V) followed by activation with thionyl chloride (SOCl2) and then condensation with excess of diamines. Structural characterization of diamide-diimide-diamines was done by using FTIR, 1H-NMR, 13C-NMR spectroscopy and elemental analysis. The peak exotherm temperature (TP) was lowest in DGEBA cured using EPSM and highest in DGEBA cured using ENSS. Thermal stability of the isothermally cured DGEBA with diamide-diimide-diamines was investigated using dynamic thermogravimetry (TGA) in nitrogen atmosphere, and it was found that NTDA based diamide-diimide-diamines provided good stability to DGEBA. The char yield was highest for resin cured with ENSE which might be due to the presence of more compact structure i.e. naphthalene.
The curing behavior of diglycidyl ether of bisphenol-A (DGEBA) with aromatic diamide-diimide-diamines having aryl ether, sulfone and methylene linkages was studied by differential scanning calorimetry (DSC). Nine diamide-diimide-diamines of varying structure were synthesized by reacting 1 mole of dianhydride with 2 moles of L-cysteine (S) in a mixture of acetic acid and pyridine (3:2 V/V) followed by activation with thionyl chloride (SOCl2) and then condensation with excess of diamines. Structural characterization of diamide-diimide-diamines was done by using FTIR, 1H-NMR, 13C-NMR spectroscopy and elemental analysis. The peak exotherm temperature (TP) was lowest in DGEBA cured using EPSM and highest in DGEBA cured using ENSS. Thermal stability of the isothermally cured DGEBA with diamide-diimide-diamines was investigated using dynamic thermogravimetry (TGA) in nitrogen atmosphere, and it was found that NTDA based diamide-diimide-diamines provided good stability to DGEBA. The char yield was highest for resin cured with ENSE which might be due to the presence of more compact structure i.e. naphthalene.
2009, 27(5): 659-665
Abstract:
A series of titanium complexes Ar[O, E]Cp*TiCl (Cp* = C5Me5, Ar = 1,2-phenylene, E = NH (1a); Ar = 1,2-phenylene, E = O (1b); Ar = 2,2′-diphenylene, E = O (1c); Ar = 2,2′-dinaphthalene, E = O (1d)) has been prepared by the reaction of corresponding phenol derivatives with Cp*TiCl3 in the presence of excessive triethylamine. Under the conditions of low Al/Ti molar ratio (e.g. 500) and high reaction temperatures (≥ 70οC), all the titanium complexes display higher catalytic activities towards the syndiospecific polymerization of styrene, in the presence of modified methylaluminoxane (MMAO) as a cocatalyst, than their mother complex Cp*TiCl3. The catalyst activities and polymer yields as well as polymer properties are considerably affected by the steric and electronical effects of the bidentate ligands.
A series of titanium complexes Ar[O, E]Cp*TiCl (Cp* = C5Me5, Ar = 1,2-phenylene, E = NH (1a); Ar = 1,2-phenylene, E = O (1b); Ar = 2,2′-diphenylene, E = O (1c); Ar = 2,2′-dinaphthalene, E = O (1d)) has been prepared by the reaction of corresponding phenol derivatives with Cp*TiCl3 in the presence of excessive triethylamine. Under the conditions of low Al/Ti molar ratio (e.g. 500) and high reaction temperatures (≥ 70οC), all the titanium complexes display higher catalytic activities towards the syndiospecific polymerization of styrene, in the presence of modified methylaluminoxane (MMAO) as a cocatalyst, than their mother complex Cp*TiCl3. The catalyst activities and polymer yields as well as polymer properties are considerably affected by the steric and electronical effects of the bidentate ligands.
2009, 27(5): 667-674
Abstract:
Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(II) complexes was carried out in an aqueous system to give high-molecular-weight copolymers. The copolymers and emulsions were characterized by an array of techniques including NMR, GPC, TEM, WAXD and DSC. The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units, and their Mw is in the range of 105-106. By enhancing the electron withdrawing of the substituents on the phenoxy ring, the ethylene contents in the copolymers varied from 0 to 52%. The molecular weight distribution of the copolymers was bimodal. With reducing the steric effect of substituents on the aniline ring, the solid contents of the emulsions decreased. The polydispersity of the copolymer varied from 11.1 to 2.8, and the ethylene content in the copolymer was below 10%. The homopolymer of styrene was obtained when the substitutent on the aniline ring was hydrogen.
Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(II) complexes was carried out in an aqueous system to give high-molecular-weight copolymers. The copolymers and emulsions were characterized by an array of techniques including NMR, GPC, TEM, WAXD and DSC. The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units, and their Mw is in the range of 105-106. By enhancing the electron withdrawing of the substituents on the phenoxy ring, the ethylene contents in the copolymers varied from 0 to 52%. The molecular weight distribution of the copolymers was bimodal. With reducing the steric effect of substituents on the aniline ring, the solid contents of the emulsions decreased. The polydispersity of the copolymer varied from 11.1 to 2.8, and the ethylene content in the copolymer was below 10%. The homopolymer of styrene was obtained when the substitutent on the aniline ring was hydrogen.
2009, 27(5): 675-683
Abstract:
Three novel polymers incorporating Schiff bases, derived from condensation reactions of poly(acrylamide) with 5-chloro-2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde and 5-methyl-2-hydroxybenzaldehyde, have been synthesized, and their Cu(II) and Ni(II) complexes have been prepared. The 1H-NMR signals of the ―CH＝N― and ―NH2 groups have been utilized to determine the relative abundances of Schiff base and acrylamide groups in the polymers containing Schiff bases. Poly(acrylamide) incorporating Schiff bases and metal complexes thereof have been characterized by molar conductance, magnetic susceptibility and electronic and IR spectral studies. The selectivity of poly(acrylamide) incorporating Schiff bases in forming Ni(II)-aldehyde and Cu(II)-aldehyde complexes has been studied. The Cu(II) and Ni(II) contents in the metal-bearing polymer complexes were determined by the ICP-MS technique.
Three novel polymers incorporating Schiff bases, derived from condensation reactions of poly(acrylamide) with 5-chloro-2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde and 5-methyl-2-hydroxybenzaldehyde, have been synthesized, and their Cu(II) and Ni(II) complexes have been prepared. The 1H-NMR signals of the ―CH＝N― and ―NH2 groups have been utilized to determine the relative abundances of Schiff base and acrylamide groups in the polymers containing Schiff bases. Poly(acrylamide) incorporating Schiff bases and metal complexes thereof have been characterized by molar conductance, magnetic susceptibility and electronic and IR spectral studies. The selectivity of poly(acrylamide) incorporating Schiff bases in forming Ni(II)-aldehyde and Cu(II)-aldehyde complexes has been studied. The Cu(II) and Ni(II) contents in the metal-bearing polymer complexes were determined by the ICP-MS technique.
2009, 27(5): 685-694
Abstract:
Nano-sized silica particles were modified with methacryloxy-propyltrimethoxysilane (MPS) followed by in situ copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). These modified nanoparticles were compounded with polypropylene (PP) to prepare PP/silica nanocomposites. PMMA grafted on nano-silica enhances the dispersion of the nanoparticles and interfacial adhesion, decreases the size of PP spherulites in nanocomposites and leads to increasing the Young’s modulus and toughness of PP/silica nanocomposites at the same time. PBA grafted on nano-silica further improves the dispersion and the interfacial interaction, decreases the size of PP spherulites in PP/silica nanocomposite and leads to further toughening the PP/silica nanocomposite. But, its low modulus decreases the modulus of the PP/silica nanocomposite. The nanocomposites with PP and nano-silica particles modified by P(MMA-co-BA) have balanced stiffness and toughness due to the moderate modulus and solubility parameter of P(MMA-co-BA).
Nano-sized silica particles were modified with methacryloxy-propyltrimethoxysilane (MPS) followed by in situ copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). These modified nanoparticles were compounded with polypropylene (PP) to prepare PP/silica nanocomposites. PMMA grafted on nano-silica enhances the dispersion of the nanoparticles and interfacial adhesion, decreases the size of PP spherulites in nanocomposites and leads to increasing the Young’s modulus and toughness of PP/silica nanocomposites at the same time. PBA grafted on nano-silica further improves the dispersion and the interfacial interaction, decreases the size of PP spherulites in PP/silica nanocomposite and leads to further toughening the PP/silica nanocomposite. But, its low modulus decreases the modulus of the PP/silica nanocomposite. The nanocomposites with PP and nano-silica particles modified by P(MMA-co-BA) have balanced stiffness and toughness due to the moderate modulus and solubility parameter of P(MMA-co-BA).
2009, 27(5): 695-702
Abstract:
Hydrophilic surface modification of poly(phthalazinone ether sulfone ketone) (PPESK) porous membranes was achieved via surface-initiated atom transfer radical polymerization (ATRP) in aqueous medium. Prior to ATRP, chloromethyl groups were introduced onto PPESK main chains by chloromethylation. Chloromethylated PPESK (CMPPESK) was fabricated into porous membrane through phase inversion technique. Hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) brushes were grafted from CMPPESK membrane under the initiation of benzyl chloride groups on membrane surface. The results of Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) chains. Water contact angle measurements and protein adsorption experiments suggested that the hydrophilicity and anti-fouling ability of PPESK membrane were remarkably improved after the grafting of P(PEGMA) brushes. The addition of small amount of water in the reaction solvent apparently accelerated the progress of the grafting reaction. The use of CuCl2 in the catalyst system promoted the controllability of the ATRP reaction.
Hydrophilic surface modification of poly(phthalazinone ether sulfone ketone) (PPESK) porous membranes was achieved via surface-initiated atom transfer radical polymerization (ATRP) in aqueous medium. Prior to ATRP, chloromethyl groups were introduced onto PPESK main chains by chloromethylation. Chloromethylated PPESK (CMPPESK) was fabricated into porous membrane through phase inversion technique. Hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (P(PEGMA)) brushes were grafted from CMPPESK membrane under the initiation of benzyl chloride groups on membrane surface. The results of Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of P(PEGMA) chains. Water contact angle measurements and protein adsorption experiments suggested that the hydrophilicity and anti-fouling ability of PPESK membrane were remarkably improved after the grafting of P(PEGMA) brushes. The addition of small amount of water in the reaction solvent apparently accelerated the progress of the grafting reaction. The use of CuCl2 in the catalyst system promoted the controllability of the ATRP reaction.
2009, 27(5): 703-710
Abstract:
As a part of serial work about the application of a tetra-needle-shaped whisker (T-ZnOw) with a spatial structure in polymer composites, this work is focused on the effect of T-ZnOw dimension on the properties of polymer composites. Two kinds of T-ZnOw whiskers with different dimensions (big and small one) are introduced into PA6 composites. Our results show that for the big whisker and the small whisker both, the addition of T-ZnOw induces the mechanical property improvement of T-ZnOw/PA6 composites. Especially, the reinforcement effect of small whisker is more apparent than the bigger one. The toughening mechanism of T-ZnOw is comparatively studied through the analyzing of impact-fractured surface morphologies and the single-edge-single-notched 3-point-bend test. Finally, the effect of T-ZnOw on thermal properties of the composite is also investigated, and the results show that small whisker reinforced composites exhibit much higher heat deflection temperatures compared with the big whisker reinforced composites possibly due to the greater volume effect.
As a part of serial work about the application of a tetra-needle-shaped whisker (T-ZnOw) with a spatial structure in polymer composites, this work is focused on the effect of T-ZnOw dimension on the properties of polymer composites. Two kinds of T-ZnOw whiskers with different dimensions (big and small one) are introduced into PA6 composites. Our results show that for the big whisker and the small whisker both, the addition of T-ZnOw induces the mechanical property improvement of T-ZnOw/PA6 composites. Especially, the reinforcement effect of small whisker is more apparent than the bigger one. The toughening mechanism of T-ZnOw is comparatively studied through the analyzing of impact-fractured surface morphologies and the single-edge-single-notched 3-point-bend test. Finally, the effect of T-ZnOw on thermal properties of the composite is also investigated, and the results show that small whisker reinforced composites exhibit much higher heat deflection temperatures compared with the big whisker reinforced composites possibly due to the greater volume effect.
2009, 27(5): 711-717
Abstract:
Bis(imino)pyridyl Fe(II) complexes are important catalysts in ethylene oligomerization for preparing α-olefins. The metal net charge-activity relationship of bis(imino)pyridyl Fe(II) complexes was investigated by molecular mechanics (MM) and net charge equilibration (QEq) method with modified Dreiding force field. It was found that metal net charge was in reverse ratio to ethylene oligomerization activity. Electron-donor substituents with less steric hindrance to the central metal were favorable to Fe complex activity. Metal net charge-activity relationship could be used to assist the design of new Fe oligomerization catalysts with higher activity.
Bis(imino)pyridyl Fe(II) complexes are important catalysts in ethylene oligomerization for preparing α-olefins. The metal net charge-activity relationship of bis(imino)pyridyl Fe(II) complexes was investigated by molecular mechanics (MM) and net charge equilibration (QEq) method with modified Dreiding force field. It was found that metal net charge was in reverse ratio to ethylene oligomerization activity. Electron-donor substituents with less steric hindrance to the central metal were favorable to Fe complex activity. Metal net charge-activity relationship could be used to assist the design of new Fe oligomerization catalysts with higher activity.
2009, 27(5): 719-728
Abstract:
The toughness of blends composed of nylon 6 and acrylonitrile-butadiene-styrene (ABS) compatibilized by using styrene-maleic anhydride (SMA) as a compatibilizer was measured over a wide temperature region. Results reveal that the combining effects of particle size and volume fraction of ABS on the toughness of nylon 6/ABS/SMA blends can be described through plotting brittle-ductile transition of the impact strength versus the interparticle distance (ID) on the assumption that ABS domains relieve the triaxial tension via internal cavitation or interfacial debonding. Moreover, the effect of interfacial adhesion on fracture behavior of nylon 6/ABS/SMA blends strongly depends upon the testing temperature. The difference of relation amomg temperature, fracture behavior and interfacial adhesion can be understood in terms of the deformation mechanisms, i.e. in the case of poor interfacial adhesion, the toughness lies on whether debonding existing at the interface relieves triaxial tension or not. It is believed that for good interfacial adhesion, internal cavitation followed by matrix shear yielding is a predominant factor for toughening. Furthermore, the fracture surface of these blends was probed to elucidate how interfacial adhesion affected the impact strength of the blends.
The toughness of blends composed of nylon 6 and acrylonitrile-butadiene-styrene (ABS) compatibilized by using styrene-maleic anhydride (SMA) as a compatibilizer was measured over a wide temperature region. Results reveal that the combining effects of particle size and volume fraction of ABS on the toughness of nylon 6/ABS/SMA blends can be described through plotting brittle-ductile transition of the impact strength versus the interparticle distance (ID) on the assumption that ABS domains relieve the triaxial tension via internal cavitation or interfacial debonding. Moreover, the effect of interfacial adhesion on fracture behavior of nylon 6/ABS/SMA blends strongly depends upon the testing temperature. The difference of relation amomg temperature, fracture behavior and interfacial adhesion can be understood in terms of the deformation mechanisms, i.e. in the case of poor interfacial adhesion, the toughness lies on whether debonding existing at the interface relieves triaxial tension or not. It is believed that for good interfacial adhesion, internal cavitation followed by matrix shear yielding is a predominant factor for toughening. Furthermore, the fracture surface of these blends was probed to elucidate how interfacial adhesion affected the impact strength of the blends.
2009, 27(5): 729-737
Abstract:
Inclusion complexes (ICs) composed of α-cyclodextrins (α-CD) and biodegradable comblike copolymers with poly(α,β-malic acid) (PMA) backbones and methylated poly(ethylene glycol) (mPEG) side chains were prepared by the host-guest reaction. Two series of ICs with mPEG750 and mPEG2000 were prepared. The stoichiometry (EG/CD) of all the ICs in mPEG2000 series was 3.1, no matter what the graft degree was. While in mPEG750 series, the stoichiometry (EG/CD) was very different; it increased with the amount of mPEG decreasing. The decomposition temperatures of the fragments in ICs were closely related to graft degrees. The stack of α-CDs in ICs was a channel-type structure. The crystal of ICs was lamellar, and it could be reorganized to well-defined supermolecular structure.
Inclusion complexes (ICs) composed of α-cyclodextrins (α-CD) and biodegradable comblike copolymers with poly(α,β-malic acid) (PMA) backbones and methylated poly(ethylene glycol) (mPEG) side chains were prepared by the host-guest reaction. Two series of ICs with mPEG750 and mPEG2000 were prepared. The stoichiometry (EG/CD) of all the ICs in mPEG2000 series was 3.1, no matter what the graft degree was. While in mPEG750 series, the stoichiometry (EG/CD) was very different; it increased with the amount of mPEG decreasing. The decomposition temperatures of the fragments in ICs were closely related to graft degrees. The stack of α-CDs in ICs was a channel-type structure. The crystal of ICs was lamellar, and it could be reorganized to well-defined supermolecular structure.
2009, 27(5): 739-746
Abstract:
Biodegradable composite films based on chitosan and lignin with various composition were prepared via the solution-casting technique. FT-IR results indicate the existence of hydrogen bonding between chitosan and lignin, and SEM images show that lignin could be well dispersed in chitosan when the content of lignin is below 20 wt% due to the strong interfacial interaction. As a result of strong interaction and good dispersion, the tensile strength, storage modulus, thermal degradation temperature and glass transition temperature of chitosan have been largely improved by adding lignin. Our work provides a simple and cheap way to prepare fully biodegradable chitosan/lignin composites, which could be used as packaging films or wound dressings.
Biodegradable composite films based on chitosan and lignin with various composition were prepared via the solution-casting technique. FT-IR results indicate the existence of hydrogen bonding between chitosan and lignin, and SEM images show that lignin could be well dispersed in chitosan when the content of lignin is below 20 wt% due to the strong interfacial interaction. As a result of strong interaction and good dispersion, the tensile strength, storage modulus, thermal degradation temperature and glass transition temperature of chitosan have been largely improved by adding lignin. Our work provides a simple and cheap way to prepare fully biodegradable chitosan/lignin composites, which could be used as packaging films or wound dressings.
2009, 27(5): 747-753
Abstract:
A novelty method, frontal polymerization (FP), was employed to directly produce a series of polyacrylamide (PAM), poly(N-isopropylacrylamide) (PNIPAM) and acrylamide-N-isopropylacrylamide copolymer macroporous monoliths. Field emission scanning electronic microscope and mercury intrusion method were adopted to measure some parameters of these monoliths, such as frame, pore size distribution as well as porosity. Effects of types of monomer, thicker and surfactant on porous structure of monoliths were studied. A variety of pore morphologies, such as honeycomb, sheet and grid, was obtained by changing types of reactants. The above results allowed us to conclude that FP can be exploited as an alternative means of macroporous polymer monolithic synthesis with the additional advantages of high velocity, environmental safe and energy reduction.
A novelty method, frontal polymerization (FP), was employed to directly produce a series of polyacrylamide (PAM), poly(N-isopropylacrylamide) (PNIPAM) and acrylamide-N-isopropylacrylamide copolymer macroporous monoliths. Field emission scanning electronic microscope and mercury intrusion method were adopted to measure some parameters of these monoliths, such as frame, pore size distribution as well as porosity. Effects of types of monomer, thicker and surfactant on porous structure of monoliths were studied. A variety of pore morphologies, such as honeycomb, sheet and grid, was obtained by changing types of reactants. The above results allowed us to conclude that FP can be exploited as an alternative means of macroporous polymer monolithic synthesis with the additional advantages of high velocity, environmental safe and energy reduction.
2009, 27(5): 755-760
Abstract:
A novel proton exchange membrane (PEM) was designed and prepared from a polymer containing calix[4]arene as the functional unit to transport proton. The proton-conductivity of this membrane is about the same order of magnitude as that of Nafion 112 membrane. It is of interest to note that very different from most of the currently known PEMs, this membrane can transport proton without the help of water or other solvents. It is deduced that the protons are transported via an ion tunneling model. This opens up a new avenue for a new type of solvent-free PEMs to be applied in the development of new H2/O2 fuel cells.
A novel proton exchange membrane (PEM) was designed and prepared from a polymer containing calix[4]arene as the functional unit to transport proton. The proton-conductivity of this membrane is about the same order of magnitude as that of Nafion 112 membrane. It is of interest to note that very different from most of the currently known PEMs, this membrane can transport proton without the help of water or other solvents. It is deduced that the protons are transported via an ion tunneling model. This opens up a new avenue for a new type of solvent-free PEMs to be applied in the development of new H2/O2 fuel cells.
