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2009 Volume 27 Issue 2
2009, 27(2): 145-148
Abstract:
A new bis(aroylacetylene) containing triazole and fluorene moieties is synthesized by click chemistry. Polycyclotrimerization of the monomer is catalyzed by piperidine in refluxed dioxane, furnishing a regioregular poly(aroylarylene) in a satisfactory yield. The hyperbranched structure of the polymer is characterized spectroscopically with satisfactory results. The polymer enjoys no metal detriment and is soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, dichloromethane (DCM), and N,N-dimethylformamide (DMF).
A new bis(aroylacetylene) containing triazole and fluorene moieties is synthesized by click chemistry. Polycyclotrimerization of the monomer is catalyzed by piperidine in refluxed dioxane, furnishing a regioregular poly(aroylarylene) in a satisfactory yield. The hyperbranched structure of the polymer is characterized spectroscopically with satisfactory results. The polymer enjoys no metal detriment and is soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, dichloromethane (DCM), and N,N-dimethylformamide (DMF).
2009, 27(2): 149-155
Abstract:
TiO2-coated polystyrene nanoparticles were prepared in a simple way. First, functional PS particles were synthesized by copolymerizing one kind of polymerizable surfactant with styrene. Then the stable dispersions of polystyrene nanoparticles were used as templates, and polystyrene nanoparticles were coated with titania by in situ hydrolysis of tetra-n-butyl titanate (TBT). No surface treatment and centrifugation/redispersion cycle process were needed during the whole experiment. Isolated PS spheres with uniform coatings of titania were obtained when water concentration was lower than a certain level.
TiO2-coated polystyrene nanoparticles were prepared in a simple way. First, functional PS particles were synthesized by copolymerizing one kind of polymerizable surfactant with styrene. Then the stable dispersions of polystyrene nanoparticles were used as templates, and polystyrene nanoparticles were coated with titania by in situ hydrolysis of tetra-n-butyl titanate (TBT). No surface treatment and centrifugation/redispersion cycle process were needed during the whole experiment. Isolated PS spheres with uniform coatings of titania were obtained when water concentration was lower than a certain level.
2009, 27(2): 157-164
Abstract:
Composite membranes with polyvinyl alcohol (PVA), sulphonated poly ether ether ketone (SPEEK) and phosphotungstic acid (PWA) were prepared using solvent casting method. The proton conductivities of such membranes were found to be in the order of 10-3 S/cm in the fully hydrated condition at room temperature as measured by impedance spectroscopy. The crystalline properties were studied by X-ray diffraction analysis. The thermal properties were determined by TGA and DSC techniques. The tensile strength and percentage elongation were obtained from UTM studies. Water and methanol uptake of these membranes were studied.
Composite membranes with polyvinyl alcohol (PVA), sulphonated poly ether ether ketone (SPEEK) and phosphotungstic acid (PWA) were prepared using solvent casting method. The proton conductivities of such membranes were found to be in the order of 10-3 S/cm in the fully hydrated condition at room temperature as measured by impedance spectroscopy. The crystalline properties were studied by X-ray diffraction analysis. The thermal properties were determined by TGA and DSC techniques. The tensile strength and percentage elongation were obtained from UTM studies. Water and methanol uptake of these membranes were studied.
2009, 27(2): 165-172
Abstract:
Ultrafiltration membranes were prepared using phenolphthalein polyarylethersulfone (PES-C), polyethersulfone (PES) and poly(phthalazinone ether sulfone ketone) (PPESK) as polymers and NMP, DMAc, DMF and DMSO as solvents by immersion precipitation via phase inversion. Experimental data of thermodynamic properties of the polymer solutions and kinetic process of membrane formation were reported. For polymer solutions with good solvents, the sequence of the viscous flow activation energy (Eη) was coincident with that of the viscosity (η), without depending on the dissolving power of the solvents (characterized by intrinsic viscosity ([η])). The cloud point of the dilute polymer solutions was related to [η] of the polymer and gave a strong influence on the gelation rate in membrane formation process. The pure water flux (J) and the bovine serum albumin (BSA) rejection (R) of PES-C, PES and PPESK membranes were measured, the pure water flux (J) of membranes significantly depended on the gelation rate. The open porosity (OP) and the maximum pore size of membrane surface were calculated, and the relationship between membrane performance and membrane pore structure was discussed.
Ultrafiltration membranes were prepared using phenolphthalein polyarylethersulfone (PES-C), polyethersulfone (PES) and poly(phthalazinone ether sulfone ketone) (PPESK) as polymers and NMP, DMAc, DMF and DMSO as solvents by immersion precipitation via phase inversion. Experimental data of thermodynamic properties of the polymer solutions and kinetic process of membrane formation were reported. For polymer solutions with good solvents, the sequence of the viscous flow activation energy (Eη) was coincident with that of the viscosity (η), without depending on the dissolving power of the solvents (characterized by intrinsic viscosity ([η])). The cloud point of the dilute polymer solutions was related to [η] of the polymer and gave a strong influence on the gelation rate in membrane formation process. The pure water flux (J) and the bovine serum albumin (BSA) rejection (R) of PES-C, PES and PPESK membranes were measured, the pure water flux (J) of membranes significantly depended on the gelation rate. The open porosity (OP) and the maximum pore size of membrane surface were calculated, and the relationship between membrane performance and membrane pore structure was discussed.
2009, 27(2): 173-181
Abstract:
The main subject of this work is about the preparation of T-ZnOw/PS composites through different methods and the evaluation of mechanical properties of the composites. Different surface modification methods of T-ZnOw whiskers, the so called wet-type modification and dry-type modification, and different molding processing methods of T-ZnOw/PS composites, namely compression molding and injection molding, have been employed. Two different coupling agents, titanate coupling agent (NDZ105) and silane coupling agent (KH560), have been used to treat T-ZnOw. Both the interface structure between T-ZnOw whiskers and PS and the distribution of integrated T-ZnOw whiskers in composites have been studied by SEM. The mechanical properties of T-ZnOw/PS composites obtained through the above different methods have been studied comparatively. Although the tensile strength of the composites decreases slightly, the impact strength and tensile modulus increase with increasing the content of T-ZnOw in the composites. Both coupling agents and molding methods have great influence on the mechanical properties of the composites. The study of the impact-fractured surface shows that craze formation in PS matrix during the impact process is the main reason for the improvement of the composite toughness.
The main subject of this work is about the preparation of T-ZnOw/PS composites through different methods and the evaluation of mechanical properties of the composites. Different surface modification methods of T-ZnOw whiskers, the so called wet-type modification and dry-type modification, and different molding processing methods of T-ZnOw/PS composites, namely compression molding and injection molding, have been employed. Two different coupling agents, titanate coupling agent (NDZ105) and silane coupling agent (KH560), have been used to treat T-ZnOw. Both the interface structure between T-ZnOw whiskers and PS and the distribution of integrated T-ZnOw whiskers in composites have been studied by SEM. The mechanical properties of T-ZnOw/PS composites obtained through the above different methods have been studied comparatively. Although the tensile strength of the composites decreases slightly, the impact strength and tensile modulus increase with increasing the content of T-ZnOw in the composites. Both coupling agents and molding methods have great influence on the mechanical properties of the composites. The study of the impact-fractured surface shows that craze formation in PS matrix during the impact process is the main reason for the improvement of the composite toughness.
2009, 27(2): 183-188
Abstract:
Dynamic rheological analysis and Fourier transform infrared spectroscopy (FTIR) were used to study the effects of thermo-oxidation on the viscoelasticity and microstructure of polyolefin elastomers (POE). It was found that dynamic storage modulus (G′) and dynamic loss modulus (G〞) at low frequency region can sensitively reflect the change of microstructure of POE, which can be seen through the “second plateau” appeared in G′ versus #61559; plots at low frequencies. The frequency dependence of loss tangent (tanδ) measured under different frequency sweeps showed that the thermo-oxidative behaviors of POE relied on the holding time. The dynamic rheology test was found to be a sensitive technique for analyzing the structural changes during thermo-oxidation of polymers.
Dynamic rheological analysis and Fourier transform infrared spectroscopy (FTIR) were used to study the effects of thermo-oxidation on the viscoelasticity and microstructure of polyolefin elastomers (POE). It was found that dynamic storage modulus (G′) and dynamic loss modulus (G〞) at low frequency region can sensitively reflect the change of microstructure of POE, which can be seen through the “second plateau” appeared in G′ versus #61559; plots at low frequencies. The frequency dependence of loss tangent (tanδ) measured under different frequency sweeps showed that the thermo-oxidative behaviors of POE relied on the holding time. The dynamic rheology test was found to be a sensitive technique for analyzing the structural changes during thermo-oxidation of polymers.
2009, 27(2): 189-193
Abstract:
The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces. An approximate method is used to obtain the solution of extensional stress in closed form in the case of steady flow. For different internal viscosities, this parametric study shows different asymptotic regimes of the extensional viscosity as a function of strain rate. This analysis may explain the attenuation of pressure drop in strong flows from a phenomenological point of view.
The dumbbell model with internal viscosity for a dilute polymer solution is investigated based on a balance of viscous drag and restoring Brownian forces. An approximate method is used to obtain the solution of extensional stress in closed form in the case of steady flow. For different internal viscosities, this parametric study shows different asymptotic regimes of the extensional viscosity as a function of strain rate. This analysis may explain the attenuation of pressure drop in strong flows from a phenomenological point of view.
2009, 27(2): 195-208
Abstract:
A Monte Carlo method was used to take thorough account of the influences of different reactivity ratios and initial feed compositions on copolymer microstructure. The model proves the lack of azeotropic behavior in systems in which rA 1 and rB 1 or vice versa; it is also able to calculate the drift in the copolymer properties: copolymer composition, and randomness parameter. Moreover, for each reactivity ratio pair given, there is a unique reaction conversion, at which macromolecules produced inherit their maximum allowed alterations. This critical conversion declines as initial feed composition increases. However, for systems with rA 1 and rB 1, as well as those with rA 1 and rB 1, the azeotropic behavior of the reactions is clearly observed. Besides, copolymer composition reaches azeotrope point at the end of the reaction when rA 1 and rB 1. Finally, for systems in which rA 1 and rB 1, randomness parameter becomes maximum at azeotrope point when rA equals rB.
A Monte Carlo method was used to take thorough account of the influences of different reactivity ratios and initial feed compositions on copolymer microstructure. The model proves the lack of azeotropic behavior in systems in which rA 1 and rB 1 or vice versa; it is also able to calculate the drift in the copolymer properties: copolymer composition, and randomness parameter. Moreover, for each reactivity ratio pair given, there is a unique reaction conversion, at which macromolecules produced inherit their maximum allowed alterations. This critical conversion declines as initial feed composition increases. However, for systems with rA 1 and rB 1, as well as those with rA 1 and rB 1, the azeotropic behavior of the reactions is clearly observed. Besides, copolymer composition reaches azeotrope point at the end of the reaction when rA 1 and rB 1. Finally, for systems in which rA 1 and rB 1, randomness parameter becomes maximum at azeotrope point when rA equals rB.
2009, 27(2): 209-219
Abstract:
The oxidative polycondensation reaction conditions of 4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid (4-HNMABA) with H2O2, air O2 and NaOCl were studied in an aqueous alkaline medium between 40°C and 90°C. The structure of oligo {4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid} (O-4-HNMABA) was characterized by using 1H-NMR, 13C-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. At the optimum reaction conditions, the yield of O-4-HNMABA was found to be 70% for H2O2 oxidant, 94% for air O2 oxidant and 87% for NaOCl oxidant. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-4-HNMABA were found to be 850, 1350 and 1.59, using H2O2, 1800, 2200 and 1.22, using air O2 and 2200, 3000 and 1.36, using NaOCl, respectively. TGA-DTA analyses showed that O-4-HNMABA was more stable than 4-HNMABA. The highest occupied molecular orbital, the lowest unoccupied molecular orbital and electrochemical energy gaps ( ) of 4-HNMABA and O-4-HNMABA were found to be -6.34, -6.56; -2.67, -3.04; 3.67 and 3.52 eV, respectively, by cyclic voltammetry (CV). According to UV-Vis measurements, optical band gaps (Eg) of 4-HNMABA and O-4-HNMABA were found to be 3.12 and 3.03 eV, respectively.
The oxidative polycondensation reaction conditions of 4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid (4-HNMABA) with H2O2, air O2 and NaOCl were studied in an aqueous alkaline medium between 40°C and 90°C. The structure of oligo {4-[(2-hydroxyl-1-naphthyl)methylene]aminobenzoic acid} (O-4-HNMABA) was characterized by using 1H-NMR, 13C-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. At the optimum reaction conditions, the yield of O-4-HNMABA was found to be 70% for H2O2 oxidant, 94% for air O2 oxidant and 87% for NaOCl oxidant. According to the SEC analysis, the number-average molecular weight (Mn), weight-average molecular weight (Mw) and polydispersity index (PDI) values of O-4-HNMABA were found to be 850, 1350 and 1.59, using H2O2, 1800, 2200 and 1.22, using air O2 and 2200, 3000 and 1.36, using NaOCl, respectively. TGA-DTA analyses showed that O-4-HNMABA was more stable than 4-HNMABA. The highest occupied molecular orbital, the lowest unoccupied molecular orbital and electrochemical energy gaps ( ) of 4-HNMABA and O-4-HNMABA were found to be -6.34, -6.56; -2.67, -3.04; 3.67 and 3.52 eV, respectively, by cyclic voltammetry (CV). According to UV-Vis measurements, optical band gaps (Eg) of 4-HNMABA and O-4-HNMABA were found to be 3.12 and 3.03 eV, respectively.
2009, 27(2): 221-229
Abstract:
Preform permeability is an important process parameter in liquid injection molding of composite parts. This parameter is currently determined with time consuming and expensive experimental procedures. This paper presents the application of a back-propagation neural network to predicting fiber bed permeability of three types of reinforcement mats. Resin flow experiments were performed to simulate the injection cycle of a resin transfer molding process. The results of these experiments were used to prepare a training set for the back propagation neural network program. The reinforcements consisted of plain-weave carbon, plain-weave fiberglass, and chopped fiberglass mats. The effects of reinforcement type, porosity and injection pressure on fiber bed permeability in the preform principal directions were investigated. Therefore, in the training of the neural network reinforcement type, these process parameters were used as the input data. Fiber bed permeability values were the specified output of the program. As a result of the specified parameters, the program was able to estimate fiber bed permeability in the preform principal directions for any given processing condition. The results indicate that neural network may be used to predict preform permeability.
Preform permeability is an important process parameter in liquid injection molding of composite parts. This parameter is currently determined with time consuming and expensive experimental procedures. This paper presents the application of a back-propagation neural network to predicting fiber bed permeability of three types of reinforcement mats. Resin flow experiments were performed to simulate the injection cycle of a resin transfer molding process. The results of these experiments were used to prepare a training set for the back propagation neural network program. The reinforcements consisted of plain-weave carbon, plain-weave fiberglass, and chopped fiberglass mats. The effects of reinforcement type, porosity and injection pressure on fiber bed permeability in the preform principal directions were investigated. Therefore, in the training of the neural network reinforcement type, these process parameters were used as the input data. Fiber bed permeability values were the specified output of the program. As a result of the specified parameters, the program was able to estimate fiber bed permeability in the preform principal directions for any given processing condition. The results indicate that neural network may be used to predict preform permeability.
2009, 27(2): 231-239
Abstract:
Polysaccharide coated PLA nanoparticles bearing aldehyde groups were prepared by dialysis of DMSO solution of cholesterol hydrophobic-modified dextran polyaldehyde and PLA against water. The average diameter of the nanoparticles was about 160 nm, and the size distribution was nearly homogenous. The nanoparticles were functionalized simultaneously with CD71 and EGFR antibody through the Schiff’s base reaction, and then radiolabeled with 99mTc. After perfused the radiolabeled nanoparticles into tumor-bearing rats through left common carotid artery, the radioactivity in liver, spleen, kidney and brain was measured by scintillation counter. The results showed that less than 2% of nanoparticles were uptaken by the brain due to the uptake of the nanoparticles by the RES system. However, the coupling of transferrin antibody on the nanoparticles facilitated the penetration of nanoparticles across the blood brain barrier, and more specially, compared with monofuctionalized and native nanoparticles, the multifunctionalization enhanced the tumor accumulation of the nanoparticles in vivo.
Polysaccharide coated PLA nanoparticles bearing aldehyde groups were prepared by dialysis of DMSO solution of cholesterol hydrophobic-modified dextran polyaldehyde and PLA against water. The average diameter of the nanoparticles was about 160 nm, and the size distribution was nearly homogenous. The nanoparticles were functionalized simultaneously with CD71 and EGFR antibody through the Schiff’s base reaction, and then radiolabeled with 99mTc. After perfused the radiolabeled nanoparticles into tumor-bearing rats through left common carotid artery, the radioactivity in liver, spleen, kidney and brain was measured by scintillation counter. The results showed that less than 2% of nanoparticles were uptaken by the brain due to the uptake of the nanoparticles by the RES system. However, the coupling of transferrin antibody on the nanoparticles facilitated the penetration of nanoparticles across the blood brain barrier, and more specially, compared with monofuctionalized and native nanoparticles, the multifunctionalization enhanced the tumor accumulation of the nanoparticles in vivo.
2009, 27(2): 241-252
Abstract:
A novel intumnescent flame melamine salt of dipentaerythriol phosphate (MDP), was prepared from dipentaerythritol (DPE) polyphosphoric acid, and melamine. The flammability, combustion behavior, and thermal degradation and stability of PP-MDP were characterized. When MDP loading was 20 wt%, LOI values of the composites reached up to 27%, and UL94 rating, V-2. PP-MDP containing 1 wt% Cu-ZSM-5 presented the highest LOI value of 30.5% and UL94 rating, V-0, and released lest heat during cone test. TG data showed that the thermal degradation of PP was improved by the addition of MDP. While the loading of ZSM-5 was 1 wt% or higher, the main weight loss delayed with 50oC, and 80oC, compared with PP and PP-MDP respectively. The appropriate loading Cu-ZSM-5 made PP-MDP possess higher thermal oxidative stability. By SEM, the formation of a dense and thick char layer was observed on the char layer of PP-MDP-containing Cu-ZSM-5, responsible for high flame retardancy. So, the synergistic flame retardancy effects of MDP and Cu-ZSM-5 on PP existed. The mechanism of synergistic effect of Cu-ZSM-5 zeolite on flame retarded PP by MDP was discussed.
A novel intumnescent flame melamine salt of dipentaerythriol phosphate (MDP), was prepared from dipentaerythritol (DPE) polyphosphoric acid, and melamine. The flammability, combustion behavior, and thermal degradation and stability of PP-MDP were characterized. When MDP loading was 20 wt%, LOI values of the composites reached up to 27%, and UL94 rating, V-2. PP-MDP containing 1 wt% Cu-ZSM-5 presented the highest LOI value of 30.5% and UL94 rating, V-0, and released lest heat during cone test. TG data showed that the thermal degradation of PP was improved by the addition of MDP. While the loading of ZSM-5 was 1 wt% or higher, the main weight loss delayed with 50oC, and 80oC, compared with PP and PP-MDP respectively. The appropriate loading Cu-ZSM-5 made PP-MDP possess higher thermal oxidative stability. By SEM, the formation of a dense and thick char layer was observed on the char layer of PP-MDP-containing Cu-ZSM-5, responsible for high flame retardancy. So, the synergistic flame retardancy effects of MDP and Cu-ZSM-5 on PP existed. The mechanism of synergistic effect of Cu-ZSM-5 zeolite on flame retarded PP by MDP was discussed.
2009, 27(2): 253-265
Abstract:
The elastic behavior of protein-like chains was investigated by using the Pruned-Enriched-Rosenbluth Method (PERM). Three typical protein-like chains such as all-α, all-α, and α +β(α/β)proteins were studied in our modified orientation dependent monomer-monomer interaction (ODI) model. We calculated the ratio of R2/N and shape factor δ* of protein-like chains in the process of elongation. In the meantime, we discussed the average energy per bond U/N, average contact energy per bond Uc/N, average helical energy per bond Uh/N and average sheet energy per bond Ub/N. Three maps of contact formation, -helix formation, β-sheet formation were depicted. All the results educe a view that the helix structure is the most stable structure, while the other two structures are easy to be destroyed. Besides, the average Helmholtz free energy per bond A/Nis was presented. The force f obtained from the free energy was also discussed. It was shown that the chain extended itself spontaneously first. The force was studied in the process of elongation. Lastly, the energy contribution to elastic force fu was calculated too. It was noted that fu for all-β chains increased first, and then decreased with x0 increasing.
The elastic behavior of protein-like chains was investigated by using the Pruned-Enriched-Rosenbluth Method (PERM). Three typical protein-like chains such as all-α, all-α, and α +β(α/β)proteins were studied in our modified orientation dependent monomer-monomer interaction (ODI) model. We calculated the ratio of R2/N and shape factor δ* of protein-like chains in the process of elongation. In the meantime, we discussed the average energy per bond U/N, average contact energy per bond Uc/N, average helical energy per bond Uh/N and average sheet energy per bond Ub/N. Three maps of contact formation, -helix formation, β-sheet formation were depicted. All the results educe a view that the helix structure is the most stable structure, while the other two structures are easy to be destroyed. Besides, the average Helmholtz free energy per bond A/Nis was presented. The force f obtained from the free energy was also discussed. It was shown that the chain extended itself spontaneously first. The force was studied in the process of elongation. Lastly, the energy contribution to elastic force fu was calculated too. It was noted that fu for all-β chains increased first, and then decreased with x0 increasing.
2009, 27(2): 267-274
Abstract:
A new type of SiO2-MgO-CaO (SMC) whisker was used to modify high density polyethylene (HDPE). The melting behavior and crystallinity were investigated by differential scanning calorimetry (DSC). The dispersion of whiskers and interfacial adhesion in the prepared HDPE/SMC whisker composites were investigated by scanning electron microscopy (SEM). The mechanical properties were evaluated by mechanical tests and dynamic mechanical analysis (DMA). DSC data indicated that the melting temperature and the crystallinity of HDPE/SMC whisker composites kept almost constant with the addition of SMC whisker. SEM results revealed that SMC whisker could be well-dispersed in HDPE matrix and had a good interfacial interaction with HDPE, even up to a high content of 30 wt%. Mechanical tests showed that the tensile strength, tensile modulus and flexural strength of HDPE were significantly improved by the addition of SMC whisker. DMA results indicated a much enhanced storage modulus, loss modulus and loss factor. By comparing the literature data from other filler-reinforced HDPE, our work suggested that SMC whisker could be one of the best reinforcing agents for the modification of HDPE.
A new type of SiO2-MgO-CaO (SMC) whisker was used to modify high density polyethylene (HDPE). The melting behavior and crystallinity were investigated by differential scanning calorimetry (DSC). The dispersion of whiskers and interfacial adhesion in the prepared HDPE/SMC whisker composites were investigated by scanning electron microscopy (SEM). The mechanical properties were evaluated by mechanical tests and dynamic mechanical analysis (DMA). DSC data indicated that the melting temperature and the crystallinity of HDPE/SMC whisker composites kept almost constant with the addition of SMC whisker. SEM results revealed that SMC whisker could be well-dispersed in HDPE matrix and had a good interfacial interaction with HDPE, even up to a high content of 30 wt%. Mechanical tests showed that the tensile strength, tensile modulus and flexural strength of HDPE were significantly improved by the addition of SMC whisker. DMA results indicated a much enhanced storage modulus, loss modulus and loss factor. By comparing the literature data from other filler-reinforced HDPE, our work suggested that SMC whisker could be one of the best reinforcing agents for the modification of HDPE.
2009, 27(2): 275-284
Abstract:
Poly(divinylbenzene-co-acrylic acid) (poly(DVB-co-AA)) hollow microspheres with gold nanoparticles on the interior surfaces were prepared from the gold nanoparticles-coated poly(methacrylic acid) (PMAA@Au@poly(DVB-co-AA)) core-shell microspheres by removal of the PMAA core in water. Au nanoparticles-coated PMAA microspheres were afforded by the in-situ reduction of gold trichloride with PMAA microsphere as stabilizer via the interaction between carboxylic acid groups and Au nanoparticles. Gold nanoparticles-coated (PMAA@Au@poly(DVB-co-AA)) microspheres were formed during the distillation precipitation copolymerization of divinylbenzene and acrylic acid in acetonitrile with Au-coated PMAA microspheres as seeds. The thickness of the poly(DVB-co-AA) shell-layer was controlled by the amount of the solvent distilled off the polymerization system. The PMAA microspheres, Au nanoparticles-coated PMAA microspheres, core-shell microspheres, and hollow microspheres with Au nanoparticles on the interior surfaces were studied by transmission electron microscopy and scanning electron microscopy. The stabilization to L-cysteine and the preliminary catalytic property of the Au nanoparticles on the inner surface of hollow poly(DVB-co-AA) microspheres were investigated.
Poly(divinylbenzene-co-acrylic acid) (poly(DVB-co-AA)) hollow microspheres with gold nanoparticles on the interior surfaces were prepared from the gold nanoparticles-coated poly(methacrylic acid) (PMAA@Au@poly(DVB-co-AA)) core-shell microspheres by removal of the PMAA core in water. Au nanoparticles-coated PMAA microspheres were afforded by the in-situ reduction of gold trichloride with PMAA microsphere as stabilizer via the interaction between carboxylic acid groups and Au nanoparticles. Gold nanoparticles-coated (PMAA@Au@poly(DVB-co-AA)) microspheres were formed during the distillation precipitation copolymerization of divinylbenzene and acrylic acid in acetonitrile with Au-coated PMAA microspheres as seeds. The thickness of the poly(DVB-co-AA) shell-layer was controlled by the amount of the solvent distilled off the polymerization system. The PMAA microspheres, Au nanoparticles-coated PMAA microspheres, core-shell microspheres, and hollow microspheres with Au nanoparticles on the interior surfaces were studied by transmission electron microscopy and scanning electron microscopy. The stabilization to L-cysteine and the preliminary catalytic property of the Au nanoparticles on the inner surface of hollow poly(DVB-co-AA) microspheres were investigated.
2009, 27(2): 285-291
Abstract:
Hyperbranched vinyl polymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of a styrenic asymmetric divinyl monomer. This was achieved by using cumyl dithiobenzoate or S-dodecyl-S-(α,α′-dimethyl-α〞-acetic acid)trithiocarbonate as the chain transfer agent, 1,1′-azobis(cyclohexanecarbonitrile) or thermal initiation as a source of radicals. Cross-linking was inhibited by a rapid RAFT-based equilibrium between active propagation chains and dormant species, and thus a hyperbranched polymer with a monomer conversion as high as 80% was obtained. The hyperbranched structure and properties of the resultant polymers were characterized by a combination of 1H-NMR spectroscopy and a triple detection size exclusion chromatography (TRI-SEC). The hyperbranched vinyl polymer has a broad molecular weight distributions and a low Mark-Houwink exponent α value compared with the linear counterpart.
Hyperbranched vinyl polymers were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of a styrenic asymmetric divinyl monomer. This was achieved by using cumyl dithiobenzoate or S-dodecyl-S-(α,α′-dimethyl-α〞-acetic acid)trithiocarbonate as the chain transfer agent, 1,1′-azobis(cyclohexanecarbonitrile) or thermal initiation as a source of radicals. Cross-linking was inhibited by a rapid RAFT-based equilibrium between active propagation chains and dormant species, and thus a hyperbranched polymer with a monomer conversion as high as 80% was obtained. The hyperbranched structure and properties of the resultant polymers were characterized by a combination of 1H-NMR spectroscopy and a triple detection size exclusion chromatography (TRI-SEC). The hyperbranched vinyl polymer has a broad molecular weight distributions and a low Mark-Houwink exponent α value compared with the linear counterpart.
2009, 27(2): 293-296
Abstract:
New polymers with functionalized dihydropyrimidones were synthesized. The methacryloyl chloride was first reacted with 4-hydroxybenzaldehyde, and the affording aldehyde was upon the one-pot Biginelli reaction to afford new monomers with dihydropyrimidone as pending groups (M1, M2). Two new monomers were polymerized via radical polymerization to afford interesting color changeable polymers in different pH. The polymers were characterized by 1H-NMR and IR methods. The color changeable properties were also investigated.
New polymers with functionalized dihydropyrimidones were synthesized. The methacryloyl chloride was first reacted with 4-hydroxybenzaldehyde, and the affording aldehyde was upon the one-pot Biginelli reaction to afford new monomers with dihydropyrimidone as pending groups (M1, M2). Two new monomers were polymerized via radical polymerization to afford interesting color changeable polymers in different pH. The polymers were characterized by 1H-NMR and IR methods. The color changeable properties were also investigated.
