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2016 Volume 34 Issue 1
2016, 34(1): 1-12
doi: 10.1007/s10118-016-1724-5
Abstract:
Poly(L-lactide)(PLLA)/pristine vermiculite nanocomposites were prepared by melt blending in a twin-screw extruder, and the detailed information of vermiculite dispersion state and effect of vermiculite on thermal and mechanical properties were systematically studied. The results show that the dispersion of vermiculite in the matrix is quite well when the loading content does not exceed 3 wt%. Pristine vermiculite can obviously improve the melt-crystallization temperature during the nonisothermal crystallization. Both crystallization time span and spherulitic size of PLLA decrease with the increasing amount of vermiculite under isothermal crystallization condition by enhancing the primary nucleation of PLLA. And the adding vermiculite can also improve the tensile modulus and Izod impact strength of PLLA. The intrinsic mechanism for the nucleating effect of vermiculite on PLLA is proposed to be the epitaxial crystallization and specific interaction between vermiculite and PLLA.
Poly(L-lactide)(PLLA)/pristine vermiculite nanocomposites were prepared by melt blending in a twin-screw extruder, and the detailed information of vermiculite dispersion state and effect of vermiculite on thermal and mechanical properties were systematically studied. The results show that the dispersion of vermiculite in the matrix is quite well when the loading content does not exceed 3 wt%. Pristine vermiculite can obviously improve the melt-crystallization temperature during the nonisothermal crystallization. Both crystallization time span and spherulitic size of PLLA decrease with the increasing amount of vermiculite under isothermal crystallization condition by enhancing the primary nucleation of PLLA. And the adding vermiculite can also improve the tensile modulus and Izod impact strength of PLLA. The intrinsic mechanism for the nucleating effect of vermiculite on PLLA is proposed to be the epitaxial crystallization and specific interaction between vermiculite and PLLA.
2016, 34(1): 13-22
doi: 10.1007/s10118-016-1720-9
Abstract:
Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides (LDHs) were prepared by co-precipitation process in aqueous solution and further rehydrated to an organic modified LDH (OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient (OP) and water vapor permeability coefficient (WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.
Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides (LDHs) were prepared by co-precipitation process in aqueous solution and further rehydrated to an organic modified LDH (OLDH) in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A series of poly(propylene carbonate)(PPC)/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient (OP) and water vapor permeability coefficient (WVP) is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.
2016, 34(1): 23-33
doi: 10.1007/s10118-016-1723-6
Abstract:
Porous carbon membranes were favorably fabricated through the pyrolysis of polyacrylonitrile (PAN) precursors, which were prepared with a template-free technique-thermally induced phase separation. These carbon membranes possess hierarchical pores, including cellular macropores across the whole membranes and much small pores in the matrix as well as on the pore walls. Nitrogen adsorption indicates micropores (1.47 and 1.84 nm) and mesopores (2.21 nm) exist inside the carbon membranes, resulting in their specific surface area as large as 1062 m2/g. The carbon membranes were used to adsorb organic dyes (methyl orange, Congo red, and rhodamine B) from aqueous solutions based on their advantages of hierarchical pore structures and large specific surface area. It is particularly noteworthy that the membranes present a selective adsorption towards methyl orange, whose molecular size (1.2 nm) is smaller than those of Congo red (2.3 nm) and rhodamine B (1.8 nm). This attractive result can be attributed to the steric structure matching between the molecular size and the pore size, rather than electrostatic attraction. Furthermore, the used carbon membranes can be easily regenerated by hydrochloric acid, and their recovery adsorption ratio maintains above 90% even in the third cycle. This work may provide a new route for carbon-based adsorbents with hierarchical pores via a template-free approach, which could be promisingly applied to selectively remove dye contaminants in aqueous effluents.
Porous carbon membranes were favorably fabricated through the pyrolysis of polyacrylonitrile (PAN) precursors, which were prepared with a template-free technique-thermally induced phase separation. These carbon membranes possess hierarchical pores, including cellular macropores across the whole membranes and much small pores in the matrix as well as on the pore walls. Nitrogen adsorption indicates micropores (1.47 and 1.84 nm) and mesopores (2.21 nm) exist inside the carbon membranes, resulting in their specific surface area as large as 1062 m2/g. The carbon membranes were used to adsorb organic dyes (methyl orange, Congo red, and rhodamine B) from aqueous solutions based on their advantages of hierarchical pore structures and large specific surface area. It is particularly noteworthy that the membranes present a selective adsorption towards methyl orange, whose molecular size (1.2 nm) is smaller than those of Congo red (2.3 nm) and rhodamine B (1.8 nm). This attractive result can be attributed to the steric structure matching between the molecular size and the pore size, rather than electrostatic attraction. Furthermore, the used carbon membranes can be easily regenerated by hydrochloric acid, and their recovery adsorption ratio maintains above 90% even in the third cycle. This work may provide a new route for carbon-based adsorbents with hierarchical pores via a template-free approach, which could be promisingly applied to selectively remove dye contaminants in aqueous effluents.
2016, 34(1): 34-43
doi: 10.1007/s10118-016-1738-z
Abstract:
In this article, we designed and synthesized a series of 5-(2,6-dimethyl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxo-dihydropyrimidine-4,6(1H, 5H)-dione (PD) unit based polymers (PFTDT, CZTDT, PHTDT and THTDT) for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability (all above 377℃). Very broad absorption spectrum was also obtained from the polymer THTDT (300-850 nm). CV characterization found that these polymers owned low highest occupied molecular orbital (HOMO) energy levels (-5.39 eV for THTDT, -5.49 eV for CZTDT and -5.78 eV for PFTDT) except for PHTDT (-5.17 eV). The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.
In this article, we designed and synthesized a series of 5-(2,6-dimethyl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxo-dihydropyrimidine-4,6(1H, 5H)-dione (PD) unit based polymers (PFTDT, CZTDT, PHTDT and THTDT) for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability (all above 377℃). Very broad absorption spectrum was also obtained from the polymer THTDT (300-850 nm). CV characterization found that these polymers owned low highest occupied molecular orbital (HOMO) energy levels (-5.39 eV for THTDT, -5.49 eV for CZTDT and -5.78 eV for PFTDT) except for PHTDT (-5.17 eV). The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.
2016, 34(1): 44-51
doi: 10.1007/s10118-016-1725-4
Abstract:
We report a facile strategy for incorporating persistent and effective antibacterial property into a widely used polymer, poly(methyl methacrylate)(PMMA), by copolymerizing methyl methacrylate (MMA) with 2-(tert-butylamino)ethyl methacrylate (TA) in one pot via atom transfer radical polymerization (ATRP). The subsequent self-assembly of the resultant poly(methyl methacrylate)-block-poly[(2-tert-butylamino)ethyl methacrylate] (PMMA20-b-PTA15) diblock copolymer affords well-defined water-dispersible vesicles, which can be facilely sprayed on the walls in hospitals for effective inhibition and killing of bacteria. 1H-NMR and gel permeation chromatography (GPC) studies confirmed the successful synthesis of well-defined copolymer. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and dynamic light scattering (DLS) studies proved the formation of vesicles with narrow size distribution. DLS studies revealed the excellent stability of vesicles at various temperatures. Antibacterial tests showed effective antibacterial activities of polymer vesicles against both Gram-positive and Gram-negative bacteria. Moreover, this strategy may be extended for preparing a wide range of polymeric materials for facile antibacterial applications in many fields.
We report a facile strategy for incorporating persistent and effective antibacterial property into a widely used polymer, poly(methyl methacrylate)(PMMA), by copolymerizing methyl methacrylate (MMA) with 2-(tert-butylamino)ethyl methacrylate (TA) in one pot via atom transfer radical polymerization (ATRP). The subsequent self-assembly of the resultant poly(methyl methacrylate)-block-poly[(2-tert-butylamino)ethyl methacrylate] (PMMA20-b-PTA15) diblock copolymer affords well-defined water-dispersible vesicles, which can be facilely sprayed on the walls in hospitals for effective inhibition and killing of bacteria. 1H-NMR and gel permeation chromatography (GPC) studies confirmed the successful synthesis of well-defined copolymer. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and dynamic light scattering (DLS) studies proved the formation of vesicles with narrow size distribution. DLS studies revealed the excellent stability of vesicles at various temperatures. Antibacterial tests showed effective antibacterial activities of polymer vesicles against both Gram-positive and Gram-negative bacteria. Moreover, this strategy may be extended for preparing a wide range of polymeric materials for facile antibacterial applications in many fields.
2016, 34(1): 52-58
doi: 10.1007/s10118-016-1726-3
Abstract:
New silicon-containing phenyleneethynylene hybrid oligomers P2, P3, and P4 were synthesized via Sonogashira cross-coupling reactions of ethynyl-terminated silazane monomer N,N'-bis(4-ethynylphenyl)-1,1-diphenylsilazane (M1) and corresponding bis-(4-bromo-phenyl)-ended organosilicon unit containing monomers, respectively. These new oligomers were easily soluble in common solvents. The incorporation of flexible organosilicon units in the oligomers leads to blue-shift in both the UV-Vis absorption and fluorescence emission spectra similarly. The results of differential scanning calorimetry (DSC) indicate that the flexible units relieve the rigidity of oligomeric chain and provide favorable conformation for thermal cross-linking reactions. The oligomers show good thermal and thermal-oxidative stability from the thermogravimetric analysis (TGA), with their decomposition temperature at 10% weight loss (T10%) higher than 400℃ under both nitrogen and air atmosphere.
New silicon-containing phenyleneethynylene hybrid oligomers P2, P3, and P4 were synthesized via Sonogashira cross-coupling reactions of ethynyl-terminated silazane monomer N,N'-bis(4-ethynylphenyl)-1,1-diphenylsilazane (M1) and corresponding bis-(4-bromo-phenyl)-ended organosilicon unit containing monomers, respectively. These new oligomers were easily soluble in common solvents. The incorporation of flexible organosilicon units in the oligomers leads to blue-shift in both the UV-Vis absorption and fluorescence emission spectra similarly. The results of differential scanning calorimetry (DSC) indicate that the flexible units relieve the rigidity of oligomeric chain and provide favorable conformation for thermal cross-linking reactions. The oligomers show good thermal and thermal-oxidative stability from the thermogravimetric analysis (TGA), with their decomposition temperature at 10% weight loss (T10%) higher than 400℃ under both nitrogen and air atmosphere.
2016, 34(1): 59-68
doi: 10.1007/s10118-016-1728-1
Abstract:
Silica-supported branched polyethylenimine (Sil@PEI) is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes (K=106-107 L/mol). If the PEI is alkylated with cetyl groups (C16), the K of the resulting adsorbents (Sil@PEI@C16-x, where x is the fraction of PEI units being alkylated) is significantly improved. Optimization shows that Sil@PEI@C16-0.15 can best reduce aqueous surfactants to a residue around 10-10 mol/L; while Sil@PEI@C16-0.6 can reduce even small aqueous dyes to a residue below 10-10 mol/L, nearly 105-fold lower than that by Sil@PEI. The adsorbents are well recyclable. It is believed that in the case of dyes, the dense cetyl shell can isolate the PEI from the bulky water and thus suppress the competitive binding by water; while in the case of surfactants, the semiclosed cetyl shell can simultaneously meet electrostatic complement and hydrophobic complement to the surfactants.
Silica-supported branched polyethylenimine (Sil@PEI) is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes (K=106-107 L/mol). If the PEI is alkylated with cetyl groups (C16), the K of the resulting adsorbents (Sil@PEI@C16-x, where x is the fraction of PEI units being alkylated) is significantly improved. Optimization shows that Sil@PEI@C16-0.15 can best reduce aqueous surfactants to a residue around 10-10 mol/L; while Sil@PEI@C16-0.6 can reduce even small aqueous dyes to a residue below 10-10 mol/L, nearly 105-fold lower than that by Sil@PEI. The adsorbents are well recyclable. It is believed that in the case of dyes, the dense cetyl shell can isolate the PEI from the bulky water and thus suppress the competitive binding by water; while in the case of surfactants, the semiclosed cetyl shell can simultaneously meet electrostatic complement and hydrophobic complement to the surfactants.
2016, 34(1): 69-76
doi: 10.1007/s10118-016-1727-2
Abstract:
In this study, a series of monodispersed poly(L-lactide)(PLLA) were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight (Mn) on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy (Hm) showed a maximum value (87.1 J/g), which was the highest reported value till now. The critical temperature for change of crystal formation from -form to -form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from -to -form, but low-Mn PLLA didn't show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.
In this study, a series of monodispersed poly(L-lactide)(PLLA) were synthesized by the ring-opening polymerization with Schiff base aluminum catalyst, and the effects of the number-average molecular weight (Mn) on the crystallization and melting behaviors of PLLA were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The total crystallization rate of PLLA was Mn-dependent, which reached the maximum value for PLLA with Mn of 18.6 kg/mol. In addition, when Mn of PLLA was 18.6 kg/mol, the melting enthalpy (Hm) showed a maximum value (87.1 J/g), which was the highest reported value till now. The critical temperature for change of crystal formation from -form to -form crystals increased in the isothermal crystallization process with Mn increasing. In the reheating procedure, high-Mn PLLA demonstrated a small exothermal peak prior to the dominant melting peak, corresponding to crystal transition from -to -form, but low-Mn PLLA didn't show the peak of crystal transition. These different crystallization and melting behaviors were attributed to the different chain mobility of PLLA with different Mn.
2016, 34(1): 77-87
doi: 10.1007/s10118-016-1730-7
Abstract:
By controlling the feed ratio of CMS/styrene and the polymerization time, a series of hyperbranched copolystyrenes (HBCPS) were synthesized with comparable weight-averaged molecular weights (Mw) but different degree of branching (DB) through atom transfer radical self-condensing vinyl copolymerization (ATR-SCVCP) with CuBr/2,2'-bipyridyl as the catalyst. The resulting HBCPS samples were used to investigate the effect of branching architecture on their glass transition behavior. With the DB increased, the glass transition temperatures (Tg) of HBCPS samples measured by DMA and DSC both decreased. Their spin-lattice relaxation times (1H T1r) of protons displayed the same downtrend with increasing DB. Besides, a correlation between the Tgs and the DB was well established by all-atom molecular dynamics (MD) simulations. The values of MD-determined Tgs are little higher than the corresponding experimental ones. However, the dependence of Tgs on DB is in good agreement with the experimental results, i.e., Tg decreases both in experiments and simulations with increasing DB.
By controlling the feed ratio of CMS/styrene and the polymerization time, a series of hyperbranched copolystyrenes (HBCPS) were synthesized with comparable weight-averaged molecular weights (Mw) but different degree of branching (DB) through atom transfer radical self-condensing vinyl copolymerization (ATR-SCVCP) with CuBr/2,2'-bipyridyl as the catalyst. The resulting HBCPS samples were used to investigate the effect of branching architecture on their glass transition behavior. With the DB increased, the glass transition temperatures (Tg) of HBCPS samples measured by DMA and DSC both decreased. Their spin-lattice relaxation times (1H T1r) of protons displayed the same downtrend with increasing DB. Besides, a correlation between the Tgs and the DB was well established by all-atom molecular dynamics (MD) simulations. The values of MD-determined Tgs are little higher than the corresponding experimental ones. However, the dependence of Tgs on DB is in good agreement with the experimental results, i.e., Tg decreases both in experiments and simulations with increasing DB.
2016, 34(1): 88-93
doi: 10.1007/s10118-016-1731-6
Abstract:
We demonstrate a general approach for attaining the bottom morphology of block copolymer (BCP) thin films. In our former measurements on PS-b-PMMA films, surface morphology maps of the BCP films revealed distinct ordering regimes where the cylinders orient predominantly perpendicular or parallel to the interface and an 'intermediate' regime where these morphologies coexist. However, this earlier work did not explore the bottom morphology of BCP thin films. In this study, we investigated the block copolymer morphology near the solid substrate in the cast block copolymer film having a perpendicular cylinder morphology on the surface.
We demonstrate a general approach for attaining the bottom morphology of block copolymer (BCP) thin films. In our former measurements on PS-b-PMMA films, surface morphology maps of the BCP films revealed distinct ordering regimes where the cylinders orient predominantly perpendicular or parallel to the interface and an 'intermediate' regime where these morphologies coexist. However, this earlier work did not explore the bottom morphology of BCP thin films. In this study, we investigated the block copolymer morphology near the solid substrate in the cast block copolymer film having a perpendicular cylinder morphology on the surface.
2016, 34(1): 94-103
doi: 10.1007/s10118-016-1735-2
Abstract:
Chirality is a key factor in the biological activity of many biomolecules. Poly(L-lysine)(PLL), a polypeptide synthesized from L-lysine, is one of the mostly used cationic polymers for gene delivery. The effect of chirality of polylysine (PL) on its gene delivery remains unknown. Herein, we prepared three polylysines (PLs) with the similar molecular weight but different backbone chiralities including poly(L-lysine)(PLL), poly(D-lysine)(PDL) and poly(DL-lysine)(PDLL). The side chains of each PL were modified with propylene oxide (PO) of different chiralities including (R)PO, (S)PO and (R,S)PO. These PL-POs with distinct chirality in main and side chains could condense pDNA into polyplexes. The polyplexes had approximately the same size, zeta potential and binding ability, but showed distinct gene transfection efficiency. We found that the PLs of L-configuration in the main chain had higher transfection efficiency than that of D or DL configuration due to their faster cellular uptake, while the side chain chirality had no effect on transfection efficiency.
Chirality is a key factor in the biological activity of many biomolecules. Poly(L-lysine)(PLL), a polypeptide synthesized from L-lysine, is one of the mostly used cationic polymers for gene delivery. The effect of chirality of polylysine (PL) on its gene delivery remains unknown. Herein, we prepared three polylysines (PLs) with the similar molecular weight but different backbone chiralities including poly(L-lysine)(PLL), poly(D-lysine)(PDL) and poly(DL-lysine)(PDLL). The side chains of each PL were modified with propylene oxide (PO) of different chiralities including (R)PO, (S)PO and (R,S)PO. These PL-POs with distinct chirality in main and side chains could condense pDNA into polyplexes. The polyplexes had approximately the same size, zeta potential and binding ability, but showed distinct gene transfection efficiency. We found that the PLs of L-configuration in the main chain had higher transfection efficiency than that of D or DL configuration due to their faster cellular uptake, while the side chain chirality had no effect on transfection efficiency.
2016, 34(1): 104-110
doi: 10.1007/s10118-016-1729-0
Abstract:
-Iminophosphonamide ligated lanthanum bis(benzyl) complex (NPNDipp)La(CH2Ph-4-Me)2(THF)(NPNDipp=Ph2P(NC6H3iPr2-2,6)2), upon activation of AlEt3 and [Ph3C][B(C6F5)4], exhibited high catalytic activity and high trans-1,4 stereoselectivity for the polymerization of bio-sourced -myrcene (MY). Based on which, a series of novel trans-1,4 regulated elastomers could be generated by random/block copolymerization of MY and isoprene (IP).
-Iminophosphonamide ligated lanthanum bis(benzyl) complex (NPNDipp)La(CH2Ph-4-Me)2(THF)(NPNDipp=Ph2P(NC6H3iPr2-2,6)2), upon activation of AlEt3 and [Ph3C][B(C6F5)4], exhibited high catalytic activity and high trans-1,4 stereoselectivity for the polymerization of bio-sourced -myrcene (MY). Based on which, a series of novel trans-1,4 regulated elastomers could be generated by random/block copolymerization of MY and isoprene (IP).
2016, 34(1): 111-121
doi: 10.1007/s10118-016-1732-5
Abstract:
The effects of graphene oxide (GO) with polar groups and functionalized GO (fGO) with nonpolar groups on the isothermal crystallization of poly(L-lactide)(PLLA) were compared. Functionalized GO was obtained by grafting octadecylamine and characterized by FTIR, WAXD and TGA. Isothermal crystallization kinetics of PLLA/GO and PLLA/fGO nanocomposites were investigated by combining DSC data and Avrami equation. The results showed that fGO could improve PLLA crystallization rate more obviously than GO. By analyzing the morphology obtained from POM, SEM and TEM, it was found fGO with large layer space dispersed better in PLLA and supplied more nucleation sites than GO. Therefore, for the multilayer graphene, increasing the layer spaces is important to improve its dispersion in polymers, which will cause the crystal kinetics changing of polymers.
The effects of graphene oxide (GO) with polar groups and functionalized GO (fGO) with nonpolar groups on the isothermal crystallization of poly(L-lactide)(PLLA) were compared. Functionalized GO was obtained by grafting octadecylamine and characterized by FTIR, WAXD and TGA. Isothermal crystallization kinetics of PLLA/GO and PLLA/fGO nanocomposites were investigated by combining DSC data and Avrami equation. The results showed that fGO could improve PLLA crystallization rate more obviously than GO. By analyzing the morphology obtained from POM, SEM and TEM, it was found fGO with large layer space dispersed better in PLLA and supplied more nucleation sites than GO. Therefore, for the multilayer graphene, increasing the layer spaces is important to improve its dispersion in polymers, which will cause the crystal kinetics changing of polymers.
2016, 34(1): 122-134
doi: 10.1007/s10118-016-1733-4
Abstract:
With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride (PEPA)-terminated imide oligomers prepared by the reaction of 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA) and 3,4'-oxydianiline (3,4'-ODA) with different molecular weights (degree of polymerization: n=1-9) were formed. The resultant oligomers with different molecular weights were characterized for their chemical architecture, cure behavior, thermal properties, solubility in organic solvents and rheological characteristics. Besides, the thermal properties and tensile test of cured polyimide films were also evaluated. The imide oligomer (degree of polymerization: n=1) has some somewhat crystalline phase, and imide oligomers (degree of polymerization: n=2-9) showed excellent solubility (40 wt%) in N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) at room temperature. Furthermore, the rheological properties of imide oligomers showed very low melt viscosity and wider processing window. The cured films exhibited good thermal properties with the glass transition temperatures of 282-373℃ and 5 wt% thermal decomposition temperatures higher than 551℃ in nitrogen atmosphere. The elongation at break of the prepared films was found to be high (almost 9.3%).
With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride (PEPA)-terminated imide oligomers prepared by the reaction of 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA) and 3,4'-oxydianiline (3,4'-ODA) with different molecular weights (degree of polymerization: n=1-9) were formed. The resultant oligomers with different molecular weights were characterized for their chemical architecture, cure behavior, thermal properties, solubility in organic solvents and rheological characteristics. Besides, the thermal properties and tensile test of cured polyimide films were also evaluated. The imide oligomer (degree of polymerization: n=1) has some somewhat crystalline phase, and imide oligomers (degree of polymerization: n=2-9) showed excellent solubility (40 wt%) in N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) at room temperature. Furthermore, the rheological properties of imide oligomers showed very low melt viscosity and wider processing window. The cured films exhibited good thermal properties with the glass transition temperatures of 282-373℃ and 5 wt% thermal decomposition temperatures higher than 551℃ in nitrogen atmosphere. The elongation at break of the prepared films was found to be high (almost 9.3%).
