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2015 Volume 33 Issue 9
2015, 33(9): 1211-1224
doi: 10.1007/s10118-015-1668-1
Abstract:
The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer (IPC) were investigated. Different annealing temperatures ranging from 80 ℃ to 160 ℃ were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystalline structure changes in the IPC sample, including the iPP matrix and PE component, were investigated using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Dynamic mechanical analysis (DMA) was used to analyze the relaxation extent of IPC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing temperature (140 ℃), largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.
The effects of annealing on microstructure and mechanical properties of an impact resistant polypropylene copolymer (IPC) were investigated. Different annealing temperatures ranging from 80 ℃ to 160 ℃ were selected. The phase reorganization of IPC during annealing process was studied through morphological characterization technologies, including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystalline structure changes in the IPC sample, including the iPP matrix and PE component, were investigated using wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Dynamic mechanical analysis (DMA) was used to analyze the relaxation extent of IPC before and after annealing. The results showed that annealing induced phase reorganization in IPC and the degree of phase reorganization depended on annealing temperature. The annealed IPC samples exhibited largely increased crystallinity compared with the unannealed one. Intensified damping peak with increased molecular chain mobility was achieved for the annealed IPC samples. At an appropriate annealing temperature (140 ℃), largely enhanced impact strength was achieved for the annealed IPC sample. The toughening mechanisms were analyzed based on the phase reorganization and relaxation behavior.
2015, 33(9): 1225-1233
doi: 10.1007/s10118-015-1671-6
Abstract:
A series of cardo poly(aryl ether sulfone) copolymers bearing pendent sulfonic acid groups (SPES-X) have been prepared by a facile chemical graft method. The structure was confirmed by 1H-NMR spectra. The side-chain-type SPES-X membranes show significantly reduced swelling behavior and excellent mechanical properties as well as appropriate proton conductivity compared to the main-chain-type sulfonated polymers with similar ion exchange capacity (IEC) value. Moreover, they show methanol permeability in the range of 0.610-7-5.710-7 cm2/s which is lower than that of Nafion 117. All the results indicate that the SPES-X membranes are promising candidates for the direct methanol fuel cells.
A series of cardo poly(aryl ether sulfone) copolymers bearing pendent sulfonic acid groups (SPES-X) have been prepared by a facile chemical graft method. The structure was confirmed by 1H-NMR spectra. The side-chain-type SPES-X membranes show significantly reduced swelling behavior and excellent mechanical properties as well as appropriate proton conductivity compared to the main-chain-type sulfonated polymers with similar ion exchange capacity (IEC) value. Moreover, they show methanol permeability in the range of 0.610-7-5.710-7 cm2/s which is lower than that of Nafion 117. All the results indicate that the SPES-X membranes are promising candidates for the direct methanol fuel cells.
2015, 33(9): 1234-1244
doi: 10.1007/s10118-015-1674-3
Abstract:
Poly(ethylene terephthalate) (PET)/carbon black (CB) composite fibers with improved mechanical properties in tensile modulus and tensile strength are prepared by eletrospinning. Stable dispersions suitable for electrospinning are obtained by dispersing melt pre-compounded PET/CB composites in hexafluoroisopropanol. The fiber morphology and CB dispersion are investigated by FESEM and TEM. The addition of CB has no obvious effect on fiber diameter, and the average fiber diameters for all the samples are around 2-3 m. CB in the fibers is in the form of submicron-sized clusters. The thermal properties of the PET/CB composite fibers are evaluated by DSC, showing almost unchanged melting temperature and crystallinity. Uniaxial tensile tests are used to measure the mechanical properties of the PET/CB composite fiber mats. The fiber mats containing 1 wt%-8.5 wt% CB have significantly improved tensile modulus compared to neat PET fiber mat, showing reinforcing effect of CB. The electrical conductivity of the fiber mats has also been tested.
Poly(ethylene terephthalate) (PET)/carbon black (CB) composite fibers with improved mechanical properties in tensile modulus and tensile strength are prepared by eletrospinning. Stable dispersions suitable for electrospinning are obtained by dispersing melt pre-compounded PET/CB composites in hexafluoroisopropanol. The fiber morphology and CB dispersion are investigated by FESEM and TEM. The addition of CB has no obvious effect on fiber diameter, and the average fiber diameters for all the samples are around 2-3 m. CB in the fibers is in the form of submicron-sized clusters. The thermal properties of the PET/CB composite fibers are evaluated by DSC, showing almost unchanged melting temperature and crystallinity. Uniaxial tensile tests are used to measure the mechanical properties of the PET/CB composite fiber mats. The fiber mats containing 1 wt%-8.5 wt% CB have significantly improved tensile modulus compared to neat PET fiber mat, showing reinforcing effect of CB. The electrical conductivity of the fiber mats has also been tested.
2015, 33(9): 1245-1259
doi: 10.1007/s10118-015-1672-5
Abstract:
A series of side chain liquid crystalline polymers (SCLCPs) containing triphenylene (Tp) units in the side chains, denoted as PMTS (without spacer) and PMTnS (n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains), with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/13C-NMR, and the phase behaviors were examined by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (1D and 2D WAXD). The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3S, PMT4S and PMT6S, they formed the symmetry hexagonal columnar (H) phase owing to the decoupling effect. All of these indicated that the decoupling effect or coupling effect depended on the length of spacers, leading to the different LC phase formation mechanism.
A series of side chain liquid crystalline polymers (SCLCPs) containing triphenylene (Tp) units in the side chains, denoted as PMTS (without spacer) and PMTnS (n = 2, 3, 4, 6, which is the number of the methylene units between the main chain and Tp moieties in the side chains), with different lengths of spacers were synthesized through conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H/13C-NMR, and the phase behaviors were examined by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (1D and 2D WAXD). The molecular characterization of the polymers was performed with 1H-NMR, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The phase behaviors of the polymers have been investigated by a combination of techniques including DSC, POM, 1D and 2D WAXD. The results showed that the length of spacer has significant effects on the LC phase behavior of polymers. For PMTS and PMT2S, they displayed the columnar phase developed by the Tp moieties and the main chain as a whole due to the strong coupling effect of the Tp moieties and the main chain. For the PMT3S, PMT4S and PMT6S, they formed the symmetry hexagonal columnar (H) phase owing to the decoupling effect. All of these indicated that the decoupling effect or coupling effect depended on the length of spacers, leading to the different LC phase formation mechanism.
2015, 33(9): 1260-1270
doi: 10.1007/s10118-015-1676-1
Abstract:
Triphenylphosphine (TPP) was used as reducing agent to continuously generate the Cu(I) activator in copper(II)-catalyzed activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). For example, the polymers prepared with a molar ratio of [MMA]0/[EBiB]0/[CuCl2]0/[PMDETA]0/[TPP]0 = 500/1/0.1/0.5/0.5 had controlled molecular weights and low molecular weight distribution (Mw/Mn) values (~1.2). TPP as a commercial reducing agent provides a convenient copper-catalyzed AGET ATRP procedure for the preparation of well-defined polymers.
Triphenylphosphine (TPP) was used as reducing agent to continuously generate the Cu(I) activator in copper(II)-catalyzed activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). For example, the polymers prepared with a molar ratio of [MMA]0/[EBiB]0/[CuCl2]0/[PMDETA]0/[TPP]0 = 500/1/0.1/0.5/0.5 had controlled molecular weights and low molecular weight distribution (Mw/Mn) values (~1.2). TPP as a commercial reducing agent provides a convenient copper-catalyzed AGET ATRP procedure for the preparation of well-defined polymers.
2015, 33(9): 1271-1282
doi: 10.1007/s10118-015-1677-0
Abstract:
Microparticles with diameter within the range of Dn = 26-38 m were prepared from functional poly(ester-anhydride)s with different amount of allyl groups in the side chains, using emulsion solvent evaporation technique. Porous structure was obtained as the effect of photocrosslinking of allyl groups. 2,2-Dimetoxy-2-phenylacetophenone (DMPA) (0.5 wt%-10 wt%) was used as a photoinitiator. The crosslinking was carried out by UV irradiation during the solvent evaporation. Effectiveness of the crosslinking was characterized by the content of insoluble part of samples and it was in the range of 18%-75%. Porosity of microparticles (in the range of 76%-88%) depended on the functionality of poly(ester-anhydride)s and amount of the photoinitiator used. The most porous particles were obtained with use of 0.5 wt% of DMPA. Their flow ability expressed by Carr's index was excellent, and their theoretical mass mean aerodynamic diameters were acceptable for use in pulmonary drug delivery. The most porous particles were loaded with p-nitroaniline, theophilline or doxycycline. The loading efficiencies of drugs in porous microspheres were higher compared to nonporous ones. The porosity of loaded microparticles was slightly decreased, however their flow ability was still very good.
Microparticles with diameter within the range of Dn = 26-38 m were prepared from functional poly(ester-anhydride)s with different amount of allyl groups in the side chains, using emulsion solvent evaporation technique. Porous structure was obtained as the effect of photocrosslinking of allyl groups. 2,2-Dimetoxy-2-phenylacetophenone (DMPA) (0.5 wt%-10 wt%) was used as a photoinitiator. The crosslinking was carried out by UV irradiation during the solvent evaporation. Effectiveness of the crosslinking was characterized by the content of insoluble part of samples and it was in the range of 18%-75%. Porosity of microparticles (in the range of 76%-88%) depended on the functionality of poly(ester-anhydride)s and amount of the photoinitiator used. The most porous particles were obtained with use of 0.5 wt% of DMPA. Their flow ability expressed by Carr's index was excellent, and their theoretical mass mean aerodynamic diameters were acceptable for use in pulmonary drug delivery. The most porous particles were loaded with p-nitroaniline, theophilline or doxycycline. The loading efficiencies of drugs in porous microspheres were higher compared to nonporous ones. The porosity of loaded microparticles was slightly decreased, however their flow ability was still very good.
2015, 33(9): 1283-1293
doi: 10.1007/s10118-015-1673-4
Abstract:
Poly(butylene terephthalate)-poly(tetramethylene glycol) (PBT-PTMG) copolymer is prepared with terephthalic acid (PTA) rather than its dimethyl ester (DMT) as starting material by a two-step melt polycondensation. This process includes the synthesis of PBT prepolymer from PTA with 1,4-butanediol (BDO) in the first step, followed by the synthesis of PBT-PTMG copolymer from PBT prepolymer with PTMG in the second step. The molecular weight, composition as well as thermal and mechanical properties of the products from the two-step melt polycondensation are compared with the properties of the PBT-PTMG from the traditional one-step melt polycondensation. When the PTMG content is low, there is only slight difference in molecular weight, composition, thermal and mechanical properties among PBT-PTMG copolymers obtained from these two methods. However, when the PTMG content is high, only the two-step strategy is able to give high molecular weight products, and the products have comparable thermal and mechanical properties with those from traditional one-step strategy using DMT as starting material.
Poly(butylene terephthalate)-poly(tetramethylene glycol) (PBT-PTMG) copolymer is prepared with terephthalic acid (PTA) rather than its dimethyl ester (DMT) as starting material by a two-step melt polycondensation. This process includes the synthesis of PBT prepolymer from PTA with 1,4-butanediol (BDO) in the first step, followed by the synthesis of PBT-PTMG copolymer from PBT prepolymer with PTMG in the second step. The molecular weight, composition as well as thermal and mechanical properties of the products from the two-step melt polycondensation are compared with the properties of the PBT-PTMG from the traditional one-step melt polycondensation. When the PTMG content is low, there is only slight difference in molecular weight, composition, thermal and mechanical properties among PBT-PTMG copolymers obtained from these two methods. However, when the PTMG content is high, only the two-step strategy is able to give high molecular weight products, and the products have comparable thermal and mechanical properties with those from traditional one-step strategy using DMT as starting material.
2015, 33(9): 1294-1304
doi: 10.1007/s10118-015-1679-y
Abstract:
Polyester-based biodegradable polyurethane (PU) with different hard segment ratios was selected to modify the impact toughness of poly(L-lactide) (PLLA). The influence of blending composition and hard segment ratio of PU on the phase morphology, crystallization behavior and mechanical properties of PLLA/PU blends has been investigated systematically. The results showed that the PU particles were uniformly dispersed in PLLA matrix at a scale from sub-microns to several microns. The glass transition temperature of PU within these blends decreased compared to that of neat PU, but rose slightly with its content and hard segment ratio. The presence of PU retarded the crystallization ability of PLLA, whereas enhanced its elongation at break and impact resistance effectively. As the PU content reaches up to 30 wt%, the phenomenon of brittle-ductile transition occurred, resulting in a rougher fracture surface with the formation of fibril-like structure. Moreover, under the same concentrations, the elongation at break and impact strength of PLLA blends decreased slightly with the increase of hard segment ratio of PU.
Polyester-based biodegradable polyurethane (PU) with different hard segment ratios was selected to modify the impact toughness of poly(L-lactide) (PLLA). The influence of blending composition and hard segment ratio of PU on the phase morphology, crystallization behavior and mechanical properties of PLLA/PU blends has been investigated systematically. The results showed that the PU particles were uniformly dispersed in PLLA matrix at a scale from sub-microns to several microns. The glass transition temperature of PU within these blends decreased compared to that of neat PU, but rose slightly with its content and hard segment ratio. The presence of PU retarded the crystallization ability of PLLA, whereas enhanced its elongation at break and impact resistance effectively. As the PU content reaches up to 30 wt%, the phenomenon of brittle-ductile transition occurred, resulting in a rougher fracture surface with the formation of fibril-like structure. Moreover, under the same concentrations, the elongation at break and impact strength of PLLA blends decreased slightly with the increase of hard segment ratio of PU.
2015, 33(9): 1305-1312
doi: 10.1007/s10118-015-1678-z
Abstract:
Ladder-like polyphenylsilsesquioxanes with fairly high regularity were synthesized using an endo-template 1,2-ethylenediamine at mild temperature via direct co-hydrolysis and condensation reactions in the presence of acid catalysts in the mixture of 1,4-dioxane/H2O. The features for synthesis of ladder-like polyphenylsilsesquioxanes were investigated in detail. The products obtained were characterized by FTIR, SEC, XRD and NMR.
Ladder-like polyphenylsilsesquioxanes with fairly high regularity were synthesized using an endo-template 1,2-ethylenediamine at mild temperature via direct co-hydrolysis and condensation reactions in the presence of acid catalysts in the mixture of 1,4-dioxane/H2O. The features for synthesis of ladder-like polyphenylsilsesquioxanes were investigated in detail. The products obtained were characterized by FTIR, SEC, XRD and NMR.
2015, 33(9): 1313-1324
doi: 10.1007/s10118-015-1680-5
Abstract:
Shape memory polymer (SMP) blends based on polyurethane (PU) and polyaniline (PANI) were prepared via chemical in situ polymerization process. The thermal, mechanical, electrical and shape memory properties were investigated. The structural characterization and morphology of the polymer blends were inspected by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), respectively. The 1 wt% of PANI loading enhanced the thermal stability of the system up to 339 ℃. According to differential scanning calorimetry (DSC), the glass transition temperature (Tg) and melting temperature (Tm) of PU/PANI blends increased with the polyaniline loading (0.1 wt%-1 wt%). Improved mechanical properties such as tensile strength and Young's modulus of PU matrix were also observed with PANI. Moreover, the electrical conductivity of PU/PANI blends was also found to be a function of PANI loading. Remarkable recoverability of thermally triggered shape memory (SM) behavior to the extent of 96% was achieved for 1 wt% PANI blend.
Shape memory polymer (SMP) blends based on polyurethane (PU) and polyaniline (PANI) were prepared via chemical in situ polymerization process. The thermal, mechanical, electrical and shape memory properties were investigated. The structural characterization and morphology of the polymer blends were inspected by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM), respectively. The 1 wt% of PANI loading enhanced the thermal stability of the system up to 339 ℃. According to differential scanning calorimetry (DSC), the glass transition temperature (Tg) and melting temperature (Tm) of PU/PANI blends increased with the polyaniline loading (0.1 wt%-1 wt%). Improved mechanical properties such as tensile strength and Young's modulus of PU matrix were also observed with PANI. Moreover, the electrical conductivity of PU/PANI blends was also found to be a function of PANI loading. Remarkable recoverability of thermally triggered shape memory (SM) behavior to the extent of 96% was achieved for 1 wt% PANI blend.
2015, 33(9): 1325-1333
doi: 10.1007/s10118-015-1681-4
Abstract:
Folate-containing dextran ligand (FA-Dextran-DTPA) was synthesized by the incorporation of diethylenetriamine-pentaacetic acid (DTPA) and folate (FA) as a tumor-targeting group into dextran as a polymer carrier. This ligand was further reacted with gadolinium chloride to make a dextran gadolinium complex FA-Dextran-DTPA-Gd. The ligand and its gadolinium complex were characterized by 1H-NMR, FTIR, UV-Vis, average particle sizes and zeta potential, as well. In vitro properties including relaxivity, cytotoxicity assay, cellular uptake assay, and magnetic resonance imaging (MRI) were also evaluated. Compared with Gd-DTPA, FA-Dextran-DTPA-Gd possessed obviously higher relaxation effectiveness and lower cytotoxicity to HeLa cells. FA-Dextran-DTPA-Gd had a high affinity to the H460 and MDA-MB-231 tumor cells and can be taken up selectively by these tumor cells. Moreover, FA-Dextran-DTPA-Gd showed enhanced signal intensities (SI) of MRI and enhanced the contrast of MR images of tumor cells. These results indicated that FA-Dextran-DTPA-Gd showed the potential as a tumor-targeting contrast agent in MRI.
Folate-containing dextran ligand (FA-Dextran-DTPA) was synthesized by the incorporation of diethylenetriamine-pentaacetic acid (DTPA) and folate (FA) as a tumor-targeting group into dextran as a polymer carrier. This ligand was further reacted with gadolinium chloride to make a dextran gadolinium complex FA-Dextran-DTPA-Gd. The ligand and its gadolinium complex were characterized by 1H-NMR, FTIR, UV-Vis, average particle sizes and zeta potential, as well. In vitro properties including relaxivity, cytotoxicity assay, cellular uptake assay, and magnetic resonance imaging (MRI) were also evaluated. Compared with Gd-DTPA, FA-Dextran-DTPA-Gd possessed obviously higher relaxation effectiveness and lower cytotoxicity to HeLa cells. FA-Dextran-DTPA-Gd had a high affinity to the H460 and MDA-MB-231 tumor cells and can be taken up selectively by these tumor cells. Moreover, FA-Dextran-DTPA-Gd showed enhanced signal intensities (SI) of MRI and enhanced the contrast of MR images of tumor cells. These results indicated that FA-Dextran-DTPA-Gd showed the potential as a tumor-targeting contrast agent in MRI.
2015, 33(9): 1334-1343
doi: 10.1007/s10118-015-1682-3
Abstract:
The dissolution, crystallization and hydrolysis behaviors of polyamide 6 (PA 6) in superheated water (140 ℃ TH 200 ℃) are investigated. The hydrothermal processing of PA 6 can be divided into four regions: (I) TH 140 ℃, (II) 140 ℃ TH 155 ℃, (III) 155 ℃ TH 160 ℃ and (IV) TH 160 ℃. Below 140 ℃, the hydrothermal processing does not have obvious impact on PA 6. Between 140 ℃ and 155 ℃, an annealing effect is observed that the hydrothermally treated resin shows increased melting temperature and lamellar thickness compared with the original PA 6. Between 155 ℃ and 160 ℃, the hydrothermal processing induces both annealing and surface swelling. Above 160 ℃, PA 6 dissolves fully in the superheated water. As PA 6 dissolves in the superheated water, hydrolysis takes place and becomes more prominent at higher temperatures and longer processing time. The hydrolysis induced molecular weight decrease fits an exponential decay.
The dissolution, crystallization and hydrolysis behaviors of polyamide 6 (PA 6) in superheated water (140 ℃ TH 200 ℃) are investigated. The hydrothermal processing of PA 6 can be divided into four regions: (I) TH 140 ℃, (II) 140 ℃ TH 155 ℃, (III) 155 ℃ TH 160 ℃ and (IV) TH 160 ℃. Below 140 ℃, the hydrothermal processing does not have obvious impact on PA 6. Between 140 ℃ and 155 ℃, an annealing effect is observed that the hydrothermally treated resin shows increased melting temperature and lamellar thickness compared with the original PA 6. Between 155 ℃ and 160 ℃, the hydrothermal processing induces both annealing and surface swelling. Above 160 ℃, PA 6 dissolves fully in the superheated water. As PA 6 dissolves in the superheated water, hydrolysis takes place and becomes more prominent at higher temperatures and longer processing time. The hydrolysis induced molecular weight decrease fits an exponential decay.
2015, 33(9): 1344-1350
doi: 10.1007/s10118-015-1683-2
Abstract:
We herein report a novel approach to fabricate poly(DVB-co-VBC) one-dimentional nanomaterials with varied composition. By adjusting the monomer DVB/VBC ratio and using inert solvents, after internal cavity of the nanotubes disappears and length of the nanotubes is decreased, thus nanorods are achieved. After quaternary ammoniation from the benzyl chloride group, the exterior surface becomes hydrophilic while the interiority preserves hydrophobic. The Janus nanorods can serve as a specific vehicle to selectively collect oils from their aqueous surroundings.
We herein report a novel approach to fabricate poly(DVB-co-VBC) one-dimentional nanomaterials with varied composition. By adjusting the monomer DVB/VBC ratio and using inert solvents, after internal cavity of the nanotubes disappears and length of the nanotubes is decreased, thus nanorods are achieved. After quaternary ammoniation from the benzyl chloride group, the exterior surface becomes hydrophilic while the interiority preserves hydrophobic. The Janus nanorods can serve as a specific vehicle to selectively collect oils from their aqueous surroundings.
