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2014 Volume 32 Issue 5
2014, 32(5): 519-523
doi: 10.1007/s10118-014-1438-5
Abstract:
Crosslinked x-P(St-MAA) seed latex was first prepared via soap-free emulsion copolymerization of styrene (St) and methyl methacrylic acid (MAA) with divinyl benzene as crosslinker and ammonium persulfate as initiator, and x-P(St-MAA)/x-P(St-NaSS) core/shell latex particles were then synthesized through a novel seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) in the presence of water-soluble crosslinker N,N'-methylene bisacrylamide (BAA) using oil-soluble 2,2-azobis isobutyronitrile as initiator. TEM observation indicated that narrow dispersed core/shell latex particles were obtained, and element analysis showed that NaSS unit content in the whole particle and in the shell reached 22.8 wt% and 51.2 wt%, respectively.
Crosslinked x-P(St-MAA) seed latex was first prepared via soap-free emulsion copolymerization of styrene (St) and methyl methacrylic acid (MAA) with divinyl benzene as crosslinker and ammonium persulfate as initiator, and x-P(St-MAA)/x-P(St-NaSS) core/shell latex particles were then synthesized through a novel seeded emulsion copolymerization of St and sodium styrene sulphonate (NaSS) in the presence of water-soluble crosslinker N,N'-methylene bisacrylamide (BAA) using oil-soluble 2,2-azobis isobutyronitrile as initiator. TEM observation indicated that narrow dispersed core/shell latex particles were obtained, and element analysis showed that NaSS unit content in the whole particle and in the shell reached 22.8 wt% and 51.2 wt%, respectively.
2014, 32(5): 524-530
doi: 10.1007/s10118-014-1435-8
Abstract:
Poly(methyl methacrylate)/poly(N-isopropylacrylamide) (PMMA/PNIPAM) core-shell particles were synthesized by seeded precipitation polymerization of N-isopropylacrylamide (NIPAM) in the presence of PMMA seed particles. The anionic potassium persulfate was used as initiator, and acrylic acid as functional comonomer. It was shown that the weight ratio of the PNIPAM shell to the PMMA core can be greatly increased through continuous addition of NIPAM monomer at a relatively slow rate. PMMA/PNIPAM particles with different shell thickness were obtained by varying the amount of charged NIPAM monomers. These particles exhibited unique nonspherical core-shell morphology. PMMA core was partially coated by dense hair-like or antler-like PNIPAM shell depending on the shell thickness. The measurement of these particles' zeta potential at different temperatures showed that the absolute value of zeta potential unusually decreased as the particle size decreased with temperature.
Poly(methyl methacrylate)/poly(N-isopropylacrylamide) (PMMA/PNIPAM) core-shell particles were synthesized by seeded precipitation polymerization of N-isopropylacrylamide (NIPAM) in the presence of PMMA seed particles. The anionic potassium persulfate was used as initiator, and acrylic acid as functional comonomer. It was shown that the weight ratio of the PNIPAM shell to the PMMA core can be greatly increased through continuous addition of NIPAM monomer at a relatively slow rate. PMMA/PNIPAM particles with different shell thickness were obtained by varying the amount of charged NIPAM monomers. These particles exhibited unique nonspherical core-shell morphology. PMMA core was partially coated by dense hair-like or antler-like PNIPAM shell depending on the shell thickness. The measurement of these particles' zeta potential at different temperatures showed that the absolute value of zeta potential unusually decreased as the particle size decreased with temperature.
2014, 32(5): 531-539
doi: 10.1007/s10118-014-1440-y
Abstract:
The lower critical solution temperature (LCST) behavior of poly(acrylamide-co-diacetone acrylamide) (poly(AM-co-DAM)) copolymer in aqueous solutions was studied. The results demonstrate the LCST linearly decreases as the molar fraction of DAM (fDAM) increases. In the range of fDAM 0.36, the transmittance increases as fDAM decreases because the more hydrophilic copolymer chains can form looser aggregates with a lower refractive index. The transmittance exhibits a minimum when fDAM is less than 0.28 as the chains form micelle-like structure with a size smaller than the wavelength. The LCST decreases with the initial polymer concentration, but it levels off when the polymer concentration is high enough. Moreover, no hysteresis can be observed in the change of transmittance during the heating-cooling process because no additional hydrogen bonds are formed in the collapsed state due to the steric hindrance of the large side groups in DAM units.
The lower critical solution temperature (LCST) behavior of poly(acrylamide-co-diacetone acrylamide) (poly(AM-co-DAM)) copolymer in aqueous solutions was studied. The results demonstrate the LCST linearly decreases as the molar fraction of DAM (fDAM) increases. In the range of fDAM 0.36, the transmittance increases as fDAM decreases because the more hydrophilic copolymer chains can form looser aggregates with a lower refractive index. The transmittance exhibits a minimum when fDAM is less than 0.28 as the chains form micelle-like structure with a size smaller than the wavelength. The LCST decreases with the initial polymer concentration, but it levels off when the polymer concentration is high enough. Moreover, no hysteresis can be observed in the change of transmittance during the heating-cooling process because no additional hydrogen bonds are formed in the collapsed state due to the steric hindrance of the large side groups in DAM units.
2014, 32(5): 540-550
doi: 10.1007/s10118-014-1432-y
Abstract:
A series of drug delivery systems based on a sodium alginate derivative were prepared by mixing glycyrrhetinic acid (GA) and doxorubicin (DOX) conjugates at different ratios. GA (a liver-targeting ligand) and DOX (an antitumor drug) were both conjugated to oligomeric glycol monomethyl ether-modified sodium alginate (ALG-mOEG) for prolonged duration of action. These NP-based delivery systems exhibited active cell uptake and cytotoxicity in vitro and liver-targeted distribution and anti-tumor activity in vivo. In addition, nanoparticles with a 1:1 (W:W) ratio of GA-ALG-mOEG and DOX-ALG-mOEG (NPs-3) showed the highest cellular uptake and cytotoxicity in vitro and liver-targeted distribution and anti-tumor activity in vivo. Specifically, when mixed nanoparticles defined as NPs-3 were injected in mice, liver DOX concentration reached 61.9 g/g 3 h after injection, and AUC0- and t1/2 of DOX in liver reached 4744.9 gh/g and 49.5 h, respectively. In addition, mice receiving a single injection of NPs-3 exhibited much slower tumor growth (88.37% reduction in tumor weight) 16 days after injection compared with placebo. These results indicate that effective cancer treatment may be developed using mixed NP delivery systems with appropriate ratio of targeted ligand and drug.
A series of drug delivery systems based on a sodium alginate derivative were prepared by mixing glycyrrhetinic acid (GA) and doxorubicin (DOX) conjugates at different ratios. GA (a liver-targeting ligand) and DOX (an antitumor drug) were both conjugated to oligomeric glycol monomethyl ether-modified sodium alginate (ALG-mOEG) for prolonged duration of action. These NP-based delivery systems exhibited active cell uptake and cytotoxicity in vitro and liver-targeted distribution and anti-tumor activity in vivo. In addition, nanoparticles with a 1:1 (W:W) ratio of GA-ALG-mOEG and DOX-ALG-mOEG (NPs-3) showed the highest cellular uptake and cytotoxicity in vitro and liver-targeted distribution and anti-tumor activity in vivo. Specifically, when mixed nanoparticles defined as NPs-3 were injected in mice, liver DOX concentration reached 61.9 g/g 3 h after injection, and AUC0- and t1/2 of DOX in liver reached 4744.9 gh/g and 49.5 h, respectively. In addition, mice receiving a single injection of NPs-3 exhibited much slower tumor growth (88.37% reduction in tumor weight) 16 days after injection compared with placebo. These results indicate that effective cancer treatment may be developed using mixed NP delivery systems with appropriate ratio of targeted ligand and drug.
2014, 32(5): 551-557
doi: 10.1007/s10118-014-1430-0
Abstract:
A series of new polycalixesters (PCES) were synthesized by polyesterification of calixarene dicarboxylic acid derivatives having tertiary butyl pendant groups at the upper rim using five different diols. All polyesters were readily soluble in polar solvents such as NMP (N-methylpyrrolidone), DMF (dimethylformamide), DMSO (dimethylsulfoxide), pyridine, THF (tetrahydrofurane), HMPA (hexamethylenephosphoramide) and DMAC (dimethylacetamide). The PCES were also partially soluble in TCE (tetrachloroethane) and ethanol and they were unsoluble in aceton. The glass transition temperatures of polyesters were between 80-184 ℃, the crystallinity temperatures of polyesters were between 130-212 ℃ and the melting temperatures of polyesters were between 185-234 ℃, as determined by differential scanning calorimeter (DSC). The inherent viscosities of polyesters were obtained from 0.55 dL/mg to 0.61 dL/mg. The temperatures at 10% weight loss of polyesters ranged from 182 ℃ to 237 ℃. The temperatures at 25% weight loss of polyesters ranged from 258 ℃ to 331 ℃. The half weight loss (50%) temperatures of polyesters were among 315 ℃ to 371 ℃ and the char yields at 600 ℃ were determined within 13% to 22.3% in N2 atmosphere, as determined by thermo gravimetric analysis (TGA). The polyester, PES3, has the higher melting point (234 ℃) and higher inherent viscosity (molecular weight) than the other polyesters.
A series of new polycalixesters (PCES) were synthesized by polyesterification of calixarene dicarboxylic acid derivatives having tertiary butyl pendant groups at the upper rim using five different diols. All polyesters were readily soluble in polar solvents such as NMP (N-methylpyrrolidone), DMF (dimethylformamide), DMSO (dimethylsulfoxide), pyridine, THF (tetrahydrofurane), HMPA (hexamethylenephosphoramide) and DMAC (dimethylacetamide). The PCES were also partially soluble in TCE (tetrachloroethane) and ethanol and they were unsoluble in aceton. The glass transition temperatures of polyesters were between 80-184 ℃, the crystallinity temperatures of polyesters were between 130-212 ℃ and the melting temperatures of polyesters were between 185-234 ℃, as determined by differential scanning calorimeter (DSC). The inherent viscosities of polyesters were obtained from 0.55 dL/mg to 0.61 dL/mg. The temperatures at 10% weight loss of polyesters ranged from 182 ℃ to 237 ℃. The temperatures at 25% weight loss of polyesters ranged from 258 ℃ to 331 ℃. The half weight loss (50%) temperatures of polyesters were among 315 ℃ to 371 ℃ and the char yields at 600 ℃ were determined within 13% to 22.3% in N2 atmosphere, as determined by thermo gravimetric analysis (TGA). The polyester, PES3, has the higher melting point (234 ℃) and higher inherent viscosity (molecular weight) than the other polyesters.
2014, 32(5): 558-567
doi: 10.1007/s10118-014-1428-7
Abstract:
The effect of carbon black (CB) and graphite (G) powders on the macroscopic and nano-scale free volume properties of silicone rubber based on poly(di-methylsiloxane) (PDMS) was studied through thermal and cyclic mechanical measurements, as well as with positron annihilation lifetime spectroscopy (PALS). The melting temperature of the composites (Tm) and the endothermic enthalpy of melting (Hm) were estimated by differential scanning calorimetry (DSC). Tm and the degree of crystallinity (c) of PDMS composites were found to decrease with increasing the CB content. This can be explained due to the increase in physical cross-linking which results in a decrease in the crystallite thickness. Besides, c was found to be dependent on the filler type. Cyclic stress-strain behavior of PDMS loaded with different contents of filler has been studied. Mullins ratio (RM) was found to be dependent on the filler type and content. It was found that, RM increases with increasing the filler content due to the increase in physical cross-linking which results in a decrease in the size of free volume, as observed through a decrease of the o-Ps lifetime 3 measured by PALS. Moreover, the hysteresis in PDMS-CB composites was more pronounced than in PDMS-G composites. Furthermore, a correlation was established between the free volume Vf and the mechanical properties of PDMS composites containing different fillers. A negative correlation was observed between Vf and RM.
The effect of carbon black (CB) and graphite (G) powders on the macroscopic and nano-scale free volume properties of silicone rubber based on poly(di-methylsiloxane) (PDMS) was studied through thermal and cyclic mechanical measurements, as well as with positron annihilation lifetime spectroscopy (PALS). The melting temperature of the composites (Tm) and the endothermic enthalpy of melting (Hm) were estimated by differential scanning calorimetry (DSC). Tm and the degree of crystallinity (c) of PDMS composites were found to decrease with increasing the CB content. This can be explained due to the increase in physical cross-linking which results in a decrease in the crystallite thickness. Besides, c was found to be dependent on the filler type. Cyclic stress-strain behavior of PDMS loaded with different contents of filler has been studied. Mullins ratio (RM) was found to be dependent on the filler type and content. It was found that, RM increases with increasing the filler content due to the increase in physical cross-linking which results in a decrease in the size of free volume, as observed through a decrease of the o-Ps lifetime 3 measured by PALS. Moreover, the hysteresis in PDMS-CB composites was more pronounced than in PDMS-G composites. Furthermore, a correlation was established between the free volume Vf and the mechanical properties of PDMS composites containing different fillers. A negative correlation was observed between Vf and RM.
2014, 32(5): 568-576
doi: 10.1007/s10118-014-1429-6
Abstract:
A theoretical investigation on the pH-induced switching of mixed polyelectrolyte brushes was performed by using a molecular theory. The results indicate that the switching properties of mixed polyelectrolyte brushes are dependent on the pH values. At low pH, negatively charged chains adopt a compact conformation on the bottom of the brush while positively charged chains are highly stretched away from the surface. At high pH values, the inverse transformation takes place. The role of pH determining the polymer chains conformation and charge behavior of mixed polyelectrolyte brushes was analyzed. It is found that there exists a mechanism for reducing strong electrostatic repulsions: stretching of the chains. The H+ and OH- units play a more important role as counterions of the charged polymers do. The collapse of the polyelectrolyte chains for different pH values could be attributed to the screening of the electrostatic interactions and the counterion-mediated attractive interaction along the chains.
A theoretical investigation on the pH-induced switching of mixed polyelectrolyte brushes was performed by using a molecular theory. The results indicate that the switching properties of mixed polyelectrolyte brushes are dependent on the pH values. At low pH, negatively charged chains adopt a compact conformation on the bottom of the brush while positively charged chains are highly stretched away from the surface. At high pH values, the inverse transformation takes place. The role of pH determining the polymer chains conformation and charge behavior of mixed polyelectrolyte brushes was analyzed. It is found that there exists a mechanism for reducing strong electrostatic repulsions: stretching of the chains. The H+ and OH- units play a more important role as counterions of the charged polymers do. The collapse of the polyelectrolyte chains for different pH values could be attributed to the screening of the electrostatic interactions and the counterion-mediated attractive interaction along the chains.
2014, 32(5): 577-586
doi: 10.1007/s10118-014-1434-9
Abstract:
Carbazole-based bi-functional photorefractive polyacrylates were prepared via free radical polymerization and post-azo-coupling reaction. The structure of polymers was characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The differential scanning calorimetry (DSC) and the thermal gravimetric analysis (TGA) were used to characterize the thermal property of polymers. The results indicate that though the glass transition temperature (Tg) of polymers increases with increasing the ratio of NLO groups, the polymers with different ratios of NLO groups still all show low glass transition temperatures around 60 ℃, and good thermal stability, which are favorable to the practical application of these polymers. The gel permeation chromatographic (GPC) result indicates that these polymers all have high-molecular-weight which is favorable to the long term stability of the material. Further, these polymers have good solubility in chloroform solvent, and the solutions can easily be fabricated into optically transparent films. Gain coefficients of 75 cm-1, 185 cm-1 and 66 cm-1 can be observed at zero external electric field without any addition agent or pre-poling for polymers P-2, P-3 and P-4 respectively. The different contents of NLO groups result in the different properties of polymers P-2, P-3 and P-4.
Carbazole-based bi-functional photorefractive polyacrylates were prepared via free radical polymerization and post-azo-coupling reaction. The structure of polymers was characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The differential scanning calorimetry (DSC) and the thermal gravimetric analysis (TGA) were used to characterize the thermal property of polymers. The results indicate that though the glass transition temperature (Tg) of polymers increases with increasing the ratio of NLO groups, the polymers with different ratios of NLO groups still all show low glass transition temperatures around 60 ℃, and good thermal stability, which are favorable to the practical application of these polymers. The gel permeation chromatographic (GPC) result indicates that these polymers all have high-molecular-weight which is favorable to the long term stability of the material. Further, these polymers have good solubility in chloroform solvent, and the solutions can easily be fabricated into optically transparent films. Gain coefficients of 75 cm-1, 185 cm-1 and 66 cm-1 can be observed at zero external electric field without any addition agent or pre-poling for polymers P-2, P-3 and P-4 respectively. The different contents of NLO groups result in the different properties of polymers P-2, P-3 and P-4.
2014, 32(5): 587-594
doi: 10.1007/s10118-014-1423-z
Abstract:
In this work, some chemometrics methods are applied for the modeling and prediction of the Hildebrand solubility parameter of some polymers. A genetic algorithm (GA) method is designed for the selection of variables to construct two models using the multiple linear regression (MLR) and least square-support vector machine (LS-SVM) methods in order to predict the Hildebrand solubility parameter. The MLR method is used to build a linear relationship between the molecular descriptors and the Hildebrand solubility parameter for these compounds. Then the LS-SVM method is utilized to construct the non-linear quantitative structure-activity relationship (QSAR) models. The results obtained using the LS-SVM method are then compared with those obtained for the MLR method; it was revealed that the LS-SVM model was much better than the MLR one. The root-mean-square errors of the training set and the test set for the LS-SVM model were 0.2912 and 0.2427, and the correlation coefficients were 0.9662 and 0.9518, respectively. This paper provides a new and effective method for predicting the Hildebrand solubility parameter for some polymers, and also reveals that the LS-SVM method can be used as a powerful chemometrics tool for the quantitative structure-property relationship (QSPR) studies.
In this work, some chemometrics methods are applied for the modeling and prediction of the Hildebrand solubility parameter of some polymers. A genetic algorithm (GA) method is designed for the selection of variables to construct two models using the multiple linear regression (MLR) and least square-support vector machine (LS-SVM) methods in order to predict the Hildebrand solubility parameter. The MLR method is used to build a linear relationship between the molecular descriptors and the Hildebrand solubility parameter for these compounds. Then the LS-SVM method is utilized to construct the non-linear quantitative structure-activity relationship (QSAR) models. The results obtained using the LS-SVM method are then compared with those obtained for the MLR method; it was revealed that the LS-SVM model was much better than the MLR one. The root-mean-square errors of the training set and the test set for the LS-SVM model were 0.2912 and 0.2427, and the correlation coefficients were 0.9662 and 0.9518, respectively. This paper provides a new and effective method for predicting the Hildebrand solubility parameter for some polymers, and also reveals that the LS-SVM method can be used as a powerful chemometrics tool for the quantitative structure-property relationship (QSPR) studies.
2014, 32(5): 595-602
doi: 10.1007/s10118-014-1446-5
Abstract:
Thin films of polymer blends composed of alternating copolymer, diblock copolymer and/or homopolymer are studied using Monte Carlo simulation. A multilayer morphology is observed in the film, that is, the blended polymers assemble into individual domains arranged from interior to the surfaces of the film. The coexisting components residing throughout the neighboring domains in the film make no distinguishable interface between any neighboring domains. By this means, it forms a vertical composition gradient in the polymeric film. Being different from layer-by-layer deposition of polyelectrolyte or hydrogen bonding approach etc., the layered structure in this study is formed by polymer blending in one step. Alternating copolymers are found to be essential components to form vertical composition gradient (layered structure) in thin films.
Thin films of polymer blends composed of alternating copolymer, diblock copolymer and/or homopolymer are studied using Monte Carlo simulation. A multilayer morphology is observed in the film, that is, the blended polymers assemble into individual domains arranged from interior to the surfaces of the film. The coexisting components residing throughout the neighboring domains in the film make no distinguishable interface between any neighboring domains. By this means, it forms a vertical composition gradient in the polymeric film. Being different from layer-by-layer deposition of polyelectrolyte or hydrogen bonding approach etc., the layered structure in this study is formed by polymer blending in one step. Alternating copolymers are found to be essential components to form vertical composition gradient (layered structure) in thin films.
2014, 32(5): 603-608
doi: 10.1007/s10118-014-1436-7
Abstract:
The copolymerizations of ethylene with 10-undecen-1-ol have been investigated using vanadium precatalysts, bis(imino)pyrrolyl vanadium(Ⅲ) complexes 1-3, 2,5-C4H2N(CH=NR)2VCl2(THF)2 [R = C6H5 (1), 2,6-iPr2C6H3 (2), C6F5 (3)], and the iminopyrrolyl and b-diketiminate ones for comparison. The polar monomer was pretreated by diethylaluminium chloride (present also as the cocatalyst) before the copolymerization. The monomer reactivity ratios were evaluated using the Fineman-Ross method. The ligand structure considerably influenced the catalytic activity and tolerance towards the polar monomer, the polar monomer incorporation and the molecular weights of the resultant copolymers. The bis(imino)pyrrolyl vanadium complexes exhibited promising catalytic performance for the copolymerization, and a high catalytic activity up to 3.84 kg/mmolvh with a high comonomer incorporation of 14.0 mol% was achieved by complex 3 under mild conditions.
The copolymerizations of ethylene with 10-undecen-1-ol have been investigated using vanadium precatalysts, bis(imino)pyrrolyl vanadium(Ⅲ) complexes 1-3, 2,5-C4H2N(CH=NR)2VCl2(THF)2 [R = C6H5 (1), 2,6-iPr2C6H3 (2), C6F5 (3)], and the iminopyrrolyl and b-diketiminate ones for comparison. The polar monomer was pretreated by diethylaluminium chloride (present also as the cocatalyst) before the copolymerization. The monomer reactivity ratios were evaluated using the Fineman-Ross method. The ligand structure considerably influenced the catalytic activity and tolerance towards the polar monomer, the polar monomer incorporation and the molecular weights of the resultant copolymers. The bis(imino)pyrrolyl vanadium complexes exhibited promising catalytic performance for the copolymerization, and a high catalytic activity up to 3.84 kg/mmolvh with a high comonomer incorporation of 14.0 mol% was achieved by complex 3 under mild conditions.
2014, 32(5): 609-619
doi: 10.1007/s10118-014-1426-9
Abstract:
Photo-oxidative degradation of polypropylene/clay multifilament yarns containing different amounts of clay was investigated. These samples and pure polypropylene (PP) multifilametns were exposed to long wavelength radiations ( 300 nm) under atmospheric condition of constant temperature and relative humidity. The photo-oxidative stability was studied using FTIR spectroscopy, tensile testing and microscopy. The results indicate that the addition of clay particles decreases the stability of PP/clay composites to photo-oxidative degradation according to comparison with pure PP. From FTIR study and tensile properties, it was also found that the multifilaments with higher clay loading reveals a faster loss of mechanical properties, higher photo-oxidative product formation and more reduction in the induction time of photo-oxidation. Moreover, the crack formation on surface of irradiated filaments corresponds well to the conclusions in tensile properties and FTIR characterization.
Photo-oxidative degradation of polypropylene/clay multifilament yarns containing different amounts of clay was investigated. These samples and pure polypropylene (PP) multifilametns were exposed to long wavelength radiations ( 300 nm) under atmospheric condition of constant temperature and relative humidity. The photo-oxidative stability was studied using FTIR spectroscopy, tensile testing and microscopy. The results indicate that the addition of clay particles decreases the stability of PP/clay composites to photo-oxidative degradation according to comparison with pure PP. From FTIR study and tensile properties, it was also found that the multifilaments with higher clay loading reveals a faster loss of mechanical properties, higher photo-oxidative product formation and more reduction in the induction time of photo-oxidation. Moreover, the crack formation on surface of irradiated filaments corresponds well to the conclusions in tensile properties and FTIR characterization.
2014, 32(5): 620-632
doi: 10.1007/s10118-014-1437-6
Abstract:
This paper proposes a constitutive law and a method for characterizing highly preloaded viscoelastic materials subjected to linear (small-amplitude) vibrations. A multiplicative non-separable variables law has been suggested to model the behavior that depends on both stretch and time/frequency. This approach allows splitting the intricate combined test performed simultaneously on both stretch and frequency, generally in a limited experimental domain up to 100 Hz, into two independent tests. Thus, on one hand, the dynamic complex modulus dependent on frequency alone is evaluated on the basis of vibration tests in a large experimental domain up to 100 kHz. On the other hand, energetic parameters are determined from a quasi-static hyperelastic tensile test. The complex modulus, dependent on both stretch and frequency, is then deduced from the results acquired from uncoupled investigations. This work shows that, in extension, the elastic modulus increases with increasing stretch, and the loss factor decreases with increasing stretch; while, in compression, around the material undeformed state, the modulus increases as the stretch increases till a certain value of compression stretch (upturn point depending on material characteristics), and then the modulus decreases as the stretch increases. Globally, preload rigidifies materials but reduces their damping property. These results closely match a well-known observation in solid mechanics.
This paper proposes a constitutive law and a method for characterizing highly preloaded viscoelastic materials subjected to linear (small-amplitude) vibrations. A multiplicative non-separable variables law has been suggested to model the behavior that depends on both stretch and time/frequency. This approach allows splitting the intricate combined test performed simultaneously on both stretch and frequency, generally in a limited experimental domain up to 100 Hz, into two independent tests. Thus, on one hand, the dynamic complex modulus dependent on frequency alone is evaluated on the basis of vibration tests in a large experimental domain up to 100 kHz. On the other hand, energetic parameters are determined from a quasi-static hyperelastic tensile test. The complex modulus, dependent on both stretch and frequency, is then deduced from the results acquired from uncoupled investigations. This work shows that, in extension, the elastic modulus increases with increasing stretch, and the loss factor decreases with increasing stretch; while, in compression, around the material undeformed state, the modulus increases as the stretch increases till a certain value of compression stretch (upturn point depending on material characteristics), and then the modulus decreases as the stretch increases. Globally, preload rigidifies materials but reduces their damping property. These results closely match a well-known observation in solid mechanics.
2014, 32(5): 633-639
doi: 10.1007/s10118-014-1433-x
Abstract:
Isotactic poly(butene-1) (iPB) with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.
Isotactic poly(butene-1) (iPB) with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.
2014, 32(5): 640-649
doi: 10.1007/s10118-014-1422-0
Abstract:
The conformational and dynamic properties of polypropylene (PP) for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic (iPP), atactic (aPP) and syndiotactic (sPP) polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state (RIS) model and Lennard-Jones (LJ) potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as: iPP aPP sPP. For PP/PP blends with 50:50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular (molecular size and chain stiffness) and intermolecular (chain packing) interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.
The conformational and dynamic properties of polypropylene (PP) for both pure melts and blends with different chain tacticity were investigated by Monte Carlo simulation of isotactic (iPP), atactic (aPP) and syndiotactic (sPP) polypropylenes. The simulation of coarse-grained PP models was performed on a high coordination lattice incorporating short- and long-range intramolecular interactions from the rotational isomeric state (RIS) model and Lennard-Jones (LJ) potential function of propane pairs, respectively. The dynamics of chains in binary PP/PP mixture were investigated with the composition of C150H302 with different chain taciticity. The diffusion rates of PP with different stereochemistry are generally in the order as: iPP aPP sPP. For PP/PP blends with 50:50 wt% binary mixtures, immiscibility was observed when sPP was introduced into the mixtures. The diffusion rate of iPP and aPP became slower after mixing, while sPP diffuses significantly faster in the binary mixtures. The mobility of PP chains depends on both intramolecular (molecular size and chain stiffness) and intermolecular (chain packing) interactions. The effect of intramolecular contribution is greater than that of intermolecular contribution for iPP and aPP chains in binary mixtures. For sPP chain, intermolecular interaction has greater influence on the dynamics than intramolecular contribution.
2014, 32(5): 650-657
doi: 10.1007/s10118-014-1441-x
Abstract:
Azo dye doped polymer films were prepared on glass substrates using spin-coating technique. FTIR, UV-Vis spectra and PL measurements were recorded to characterize the structure of the metanil yellow doped PVA films. Surface morphology and thickness of the films were studied using AFM and FESEM. The magnitude of both real and imaginary parts of third-order nonlinear susceptibility 3 of metanil yellow were determined by the Z-scan technique. The nonlinear refractive index n2 and the nonlinear absorption coefficient of the azo dye doped polymer films were calculated respectively. The real part of the third-order susceptibility 3 is much larger than its imaginary part indicating that the third-order optical response of the metanil yellow doped PVA films is dominated by the optical nonlinear refractive behavior.
Azo dye doped polymer films were prepared on glass substrates using spin-coating technique. FTIR, UV-Vis spectra and PL measurements were recorded to characterize the structure of the metanil yellow doped PVA films. Surface morphology and thickness of the films were studied using AFM and FESEM. The magnitude of both real and imaginary parts of third-order nonlinear susceptibility 3 of metanil yellow were determined by the Z-scan technique. The nonlinear refractive index n2 and the nonlinear absorption coefficient of the azo dye doped polymer films were calculated respectively. The real part of the third-order susceptibility 3 is much larger than its imaginary part indicating that the third-order optical response of the metanil yellow doped PVA films is dominated by the optical nonlinear refractive behavior.
2014, 32(5): 658-666
doi: 10.1007/s10118-014-1427-8
Abstract:
This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber (SBR) with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.
This paper presents the influence of graphene on the vulcanization kinetics of styrene butadiene rubber (SBR) with dicumyl peroxide. A curemeter and a differential scanning calorimeter were used to investigate the cure kinetics, from which the kinetic parameters and apparent activation energy were obtained. It turns out that with increasing graphene loading, the induction period of the vulcanization process of SBR is remarkably reduced at low graphene loading and then levels off; on the other hand, the optimum cure time shows a monotonous decrease. As a result, the vulcanization rate is suppressed at first and then accelerated, and the corresponding activation energy increases slightly at first and then decreases. Upon adding graphene, the crosslinking density of the nanocomposites increases, because graphene takes part in the vulcanization process.
2014, 32(5): 667-674
doi: 10.1007/s10118-014-1439-4
Abstract:
The optical properties of substituted fluorenones with diverse structures have been analyzed using molecular orbital calculations in order to understand the structure-property relations. Based on theoretical predictions, synthesis of some model compounds has been attempted. The experimentally obtained optical properties are in close agreement with the theoretically obtained results.
The optical properties of substituted fluorenones with diverse structures have been analyzed using molecular orbital calculations in order to understand the structure-property relations. Based on theoretical predictions, synthesis of some model compounds has been attempted. The experimentally obtained optical properties are in close agreement with the theoretically obtained results.
