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2016 Volume 34 Issue 11
2016, 34(11): 1301-1310
doi: 10.1007/s10118-016-1844-y
Abstract:
Hydroxypropylcellulose (HPC) films were prepared by casting with cellulose nanocrystals in the presence of anionic surfactant sodium dodecylsulphate (SDS) and cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB). The cellulose nanocrystals were isolated from maize straw, a biomass source produced in huge quantities as an agrowaste in Brazil. These bionanocomposite films had good transparency and their surface hydrophilic character was evidenced by static contact angle measurements. Thermogravimetry (TGA) measurement revealed that nanocrystals and surfactants changed the thermal stability of the HPC films. Dynamic mechanical analysis (DMA) showed that the tensile storage and loss moduli of the HPC films increased by increasing the contents of cellulose nanocrystals and surfactants, especially in the case of CTAB. This good reinforcing effect of HPC matrix can be explained as due to electrostatic attractive interactions brought about by the presence of CTAB and the nanocrystals.
Hydroxypropylcellulose (HPC) films were prepared by casting with cellulose nanocrystals in the presence of anionic surfactant sodium dodecylsulphate (SDS) and cationic surfactant hexadecyltrimethyl ammonium bromide (CTAB). The cellulose nanocrystals were isolated from maize straw, a biomass source produced in huge quantities as an agrowaste in Brazil. These bionanocomposite films had good transparency and their surface hydrophilic character was evidenced by static contact angle measurements. Thermogravimetry (TGA) measurement revealed that nanocrystals and surfactants changed the thermal stability of the HPC films. Dynamic mechanical analysis (DMA) showed that the tensile storage and loss moduli of the HPC films increased by increasing the contents of cellulose nanocrystals and surfactants, especially in the case of CTAB. This good reinforcing effect of HPC matrix can be explained as due to electrostatic attractive interactions brought about by the presence of CTAB and the nanocrystals.
2016, 34(11): 1311-1318
doi: 10.1007/s10118-016-1851-z
Abstract:
Molecular aggregates in conjugated polymer (CP) solution can propagate into mesoscale morphology of the relevant film and further dominate the optoelectronic property. Herein, we probed the aggregation behavior of poly(9,9-dioctylfluorene-2,7-diyl) (PFO) and studied its influence on the photophysical property in 1,2-dichloroethane (DCE) solution, where the contents of β-phase or -aggregates increased with prolonged aging time. Thereinto, high quality β-film was fabricated from DCE solution with critical aggregate time of 6 min. The film exhibited excellent surface morphology and characteristic emission of β-phase. Meanwhile, films prepared from aged DCE solutions exhibited high crystallinity, which was promising to obtain higher photoluminance efficiency and charge transport ability simultaneously. Therefore, it is significant to get deep insight into the aggregation behavior of CP, which is involved not only with the solution-processing technology of plastic device, but also with the optoelectronic property of CP.
Molecular aggregates in conjugated polymer (CP) solution can propagate into mesoscale morphology of the relevant film and further dominate the optoelectronic property. Herein, we probed the aggregation behavior of poly(9,9-dioctylfluorene-2,7-diyl) (PFO) and studied its influence on the photophysical property in 1,2-dichloroethane (DCE) solution, where the contents of β-phase or -aggregates increased with prolonged aging time. Thereinto, high quality β-film was fabricated from DCE solution with critical aggregate time of 6 min. The film exhibited excellent surface morphology and characteristic emission of β-phase. Meanwhile, films prepared from aged DCE solutions exhibited high crystallinity, which was promising to obtain higher photoluminance efficiency and charge transport ability simultaneously. Therefore, it is significant to get deep insight into the aggregation behavior of CP, which is involved not only with the solution-processing technology of plastic device, but also with the optoelectronic property of CP.
2016, 34(11): 1319-1329
doi: 10.1007/s10118-016-1846-9
Abstract:
Bischler-Napieralski cyclization has been successfully employed to prepare planar S,N-heteroacenes (SNHs) with the analogue structures to 1,10-phenanthroline. The opto-/electrical properties and the packing modes of these S,Nheteroacenes were examined, which were dependent on the structure of the fused groups. SNH-based copolymers with high molecular weight and good solubility in common organic solvents or water have been synthesized by Suzuki-Miyaura-Schlüter polycondensation. The photophysical property studies revealed that the copolymers may be a promising chemosensor material.
Bischler-Napieralski cyclization has been successfully employed to prepare planar S,N-heteroacenes (SNHs) with the analogue structures to 1,10-phenanthroline. The opto-/electrical properties and the packing modes of these S,Nheteroacenes were examined, which were dependent on the structure of the fused groups. SNH-based copolymers with high molecular weight and good solubility in common organic solvents or water have been synthesized by Suzuki-Miyaura-Schlüter polycondensation. The photophysical property studies revealed that the copolymers may be a promising chemosensor material.
2016, 34(11): 1330-1338
doi: 10.1007/s10118-016-1852-y
Abstract:
Poly(9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one) (PPTC) was synthesized by the microwave-assisted ring-opening polymerization (MROP) of a six-membered cyclic carbonate monomer 9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one (PTC) with tin(Ⅱ) 2-ethylhexanoate (Sn(Oct)2) or aluminum isopropoxide (Al(OiPr)3) as the catalysts. The obtained polycarbonates were further reduced by apalladium/carbonate catalyst (10% Pd/C) to afford partly deprotected polycarbonates containing hydroxyl groups (HPPTC). These two types of polycarbonates were characterized by 1H-NMR, Fourier transform infrared spectroscopy (FTIR), UV, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and automatic contact-angle measurements. The influence of the feed molar ratio of monomer-to-catalyst, the microwave irradiation power and the reaction time on the polymerization was also studied. The experimental results showed that HPPTC possessed significantly higher hydrophilicity and water absorption rate than PPTC.
Poly(9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one) (PPTC) was synthesized by the microwave-assisted ring-opening polymerization (MROP) of a six-membered cyclic carbonate monomer 9-phenyl-2,4,8,10-tetraoxaspiro-[5,5]undcane-3-one (PTC) with tin(Ⅱ) 2-ethylhexanoate (Sn(Oct)2) or aluminum isopropoxide (Al(OiPr)3) as the catalysts. The obtained polycarbonates were further reduced by apalladium/carbonate catalyst (10% Pd/C) to afford partly deprotected polycarbonates containing hydroxyl groups (HPPTC). These two types of polycarbonates were characterized by 1H-NMR, Fourier transform infrared spectroscopy (FTIR), UV, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and automatic contact-angle measurements. The influence of the feed molar ratio of monomer-to-catalyst, the microwave irradiation power and the reaction time on the polymerization was also studied. The experimental results showed that HPPTC possessed significantly higher hydrophilicity and water absorption rate than PPTC.
2016, 34(11): 1339-1353
doi: 10.1007/s10118-016-1855-8
Abstract:
In this study, piperazine-modified ammonium polyphosphates (PA-APPs) with hierarchical structure were synthesized through ion exchange reaction. 1H nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectra (FTIR), elemental analysis (EA), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) confirmed that the PA-APPs with different structures were prepared successfully. Then these flame retardants were used alone as monocomponent intumescent flame retardant for low-density polyethylene (LDPE). Combustion tests demonstrated that the flameretardant efficiency of PA-APP containing about 7 wt% carbon (PA-APP7) was significantly higher than that of the other PAAPPs with more or less carbon. The flame-retarded LDPE system with 30 wt% PA-APP7 passed the UL-94 V-0 rating, and had the oxygen index (LOI) of 33.0%. Thermal analysis illustrated that the thermal decomposition behavior of PA-APP changed with incorporating different contents of PA. For all these PA-APPs, PA-APP7 showed higher thermal stability than the other PA-APP flame retardants. All the experimental results proved that PA-APP7 could reach the balance of an acid source, a blowing source, and a charring source as a mono-component intumescent flame retardant for LDPE. Further, it led to the formation of a compact intumescent char layer containing the structures of rich P-O-P, P-N-C, C=C, etc. during burning which in turn resulted in the excellent flame-retardant efficiency of PA-APP7.
In this study, piperazine-modified ammonium polyphosphates (PA-APPs) with hierarchical structure were synthesized through ion exchange reaction. 1H nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectra (FTIR), elemental analysis (EA), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) confirmed that the PA-APPs with different structures were prepared successfully. Then these flame retardants were used alone as monocomponent intumescent flame retardant for low-density polyethylene (LDPE). Combustion tests demonstrated that the flameretardant efficiency of PA-APP containing about 7 wt% carbon (PA-APP7) was significantly higher than that of the other PAAPPs with more or less carbon. The flame-retarded LDPE system with 30 wt% PA-APP7 passed the UL-94 V-0 rating, and had the oxygen index (LOI) of 33.0%. Thermal analysis illustrated that the thermal decomposition behavior of PA-APP changed with incorporating different contents of PA. For all these PA-APPs, PA-APP7 showed higher thermal stability than the other PA-APP flame retardants. All the experimental results proved that PA-APP7 could reach the balance of an acid source, a blowing source, and a charring source as a mono-component intumescent flame retardant for LDPE. Further, it led to the formation of a compact intumescent char layer containing the structures of rich P-O-P, P-N-C, C=C, etc. during burning which in turn resulted in the excellent flame-retardant efficiency of PA-APP7.
2016, 34(11): 1354-1362
doi: 10.1007/s10118-016-1838-9
Abstract:
A thermally triggered shape memory polymer composite was prepared by blending short carbon fiber (SCF) into a blend of poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS)/linear low density polyethylene (LLDPE) prior to curing. These composites have excellent processability compared with other thermosets. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were investigated to assess the thermomechanical properties of the SCF/SBS/LLDPE composite. Scanning electron microscope (SEM) imaging of the samples was performed to show the distribution of the SCF in the composite. The study specifically focused on the effect of SCF on the shape memory behavior of the SCF/SBS/LLDPE composite. The results indicated that the large amount of SCF significantly improved the mechanical property of the polymer composites while not damaging the shape memory performance. The SCF/SBS/LLDPE composites exhibited excellent shape memory behavior when the SCF content was less than 15.0 wt%. Moreover, the shape fixity ratio and shape recovery time of the SCF/SBS/LLDPE composites increased with the SCF content.
A thermally triggered shape memory polymer composite was prepared by blending short carbon fiber (SCF) into a blend of poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS)/linear low density polyethylene (LLDPE) prior to curing. These composites have excellent processability compared with other thermosets. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were investigated to assess the thermomechanical properties of the SCF/SBS/LLDPE composite. Scanning electron microscope (SEM) imaging of the samples was performed to show the distribution of the SCF in the composite. The study specifically focused on the effect of SCF on the shape memory behavior of the SCF/SBS/LLDPE composite. The results indicated that the large amount of SCF significantly improved the mechanical property of the polymer composites while not damaging the shape memory performance. The SCF/SBS/LLDPE composites exhibited excellent shape memory behavior when the SCF content was less than 15.0 wt%. Moreover, the shape fixity ratio and shape recovery time of the SCF/SBS/LLDPE composites increased with the SCF content.
2016, 34(11): 1363-1372
doi: 10.1007/s10118-016-1845-x
Abstract:
A series of fluorinated polyimide/POSS hybrid polymers (FPI-4-FPI-16) were prepared via a facile synthetic route using 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47-2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591℃ and the weight residual at 800℃ ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.
A series of fluorinated polyimide/POSS hybrid polymers (FPI-4-FPI-16) were prepared via a facile synthetic route using 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47-2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591℃ and the weight residual at 800℃ ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.
2016, 34(11): 1373-1385
doi: 10.1007/s10118-016-1843-z
Abstract:
Ultra-high molecular weight polyethylene (UHMWPE)/chitin nanocrystal (CNC) fibers were prepared. Compared with the pure UHMWPE fibers, the ultimate tensile strength and Young's modulus of UHMWPE/CNC fibers are improved by 15.7% and 49.6%, respectively, with the addition of chitin nanocrystals (CNCs) of 1 wt%. The melting temperature (Tm) of UHMWPE/CNC fibers was higher than that of pure UHMWPE fibers. Pure UHMWPE fibers and UHMWPE/CNC fibers were characterized with respect to crystallinity, orientation and kebab structure by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). It is found that the CNCs act as the shish structure in UHMWPE/CNC fibers and the kebab crystals are grown around the CNCs. There was almost no difference between pure UHMWPE fibers and UHMWPE/CNC fibers in orientation. But the degree of crystallinity of various stages of UHMWPE/CNC fibers was respectively higher than the corresponding stage of pure UHMWPE fibers. Moreover, the addition of 1 wt% CNCs improved the thickness of kebab crystals and accelerated the transformation of kebab to shish.
Ultra-high molecular weight polyethylene (UHMWPE)/chitin nanocrystal (CNC) fibers were prepared. Compared with the pure UHMWPE fibers, the ultimate tensile strength and Young's modulus of UHMWPE/CNC fibers are improved by 15.7% and 49.6%, respectively, with the addition of chitin nanocrystals (CNCs) of 1 wt%. The melting temperature (Tm) of UHMWPE/CNC fibers was higher than that of pure UHMWPE fibers. Pure UHMWPE fibers and UHMWPE/CNC fibers were characterized with respect to crystallinity, orientation and kebab structure by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). It is found that the CNCs act as the shish structure in UHMWPE/CNC fibers and the kebab crystals are grown around the CNCs. There was almost no difference between pure UHMWPE fibers and UHMWPE/CNC fibers in orientation. But the degree of crystallinity of various stages of UHMWPE/CNC fibers was respectively higher than the corresponding stage of pure UHMWPE fibers. Moreover, the addition of 1 wt% CNCs improved the thickness of kebab crystals and accelerated the transformation of kebab to shish.
2016, 34(11): 1386-1395
doi: 10.1007/s10118-016-1841-1
Abstract:
A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.
A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.
2016, 34(11): 1396-1410
doi: 10.1007/s10118-016-1853-x
Abstract:
Molecular dynamics simulations have been performed on the aqueous solutions of poly(vinyl methyl ether) (PVME) at various concentrations. Both radial and spatial distribution functions are used to investigate the detailed hydration structures. The structures of water are found to get increasingly concentrated when polymers are introduced and the water motions are severely hindered by the polymer matrix. At low concentrations, larger populations of tt conformers in meso dyads than those at higher concentrationsare found and this phenomenon is believed to be due to the increasing in bonding of water molecule to two ether oxygens in meso dyad. At higher concentrations, the size and conformations of polymers are quite similar to those in bulk. A transition of hydrogen bond fractions between PVME and water at around the concentration of 0.3 is observed and this value is perfectly in agreement with the results of conformational analysis and Raman spectra. Second neighbor hydrogen bond statistics revealed the domination of complicated hydrogen bond networks at low concentrations, but single hydrogen bonds as well as isolated clusters composed of 2-4 water molecules are usual around each polymer repeat unit.
Molecular dynamics simulations have been performed on the aqueous solutions of poly(vinyl methyl ether) (PVME) at various concentrations. Both radial and spatial distribution functions are used to investigate the detailed hydration structures. The structures of water are found to get increasingly concentrated when polymers are introduced and the water motions are severely hindered by the polymer matrix. At low concentrations, larger populations of tt conformers in meso dyads than those at higher concentrationsare found and this phenomenon is believed to be due to the increasing in bonding of water molecule to two ether oxygens in meso dyad. At higher concentrations, the size and conformations of polymers are quite similar to those in bulk. A transition of hydrogen bond fractions between PVME and water at around the concentration of 0.3 is observed and this value is perfectly in agreement with the results of conformational analysis and Raman spectra. Second neighbor hydrogen bond statistics revealed the domination of complicated hydrogen bond networks at low concentrations, but single hydrogen bonds as well as isolated clusters composed of 2-4 water molecules are usual around each polymer repeat unit.
