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2018 Volume Issue 12
2018, 0(12): 1467-1481
doi: 10.11777/j.issn1000-3304.2018.18199
Abstract:
Polymer brush generally refers to a kind of special macromolecular structures, of which polymer chains are densely tethered to another polymer chain (one-dimension, 1-D), the surface of a planar (two-dimension, 2-D), a spherical or a cylindrical (three-dimension, 3-D) solid matrice via stable covalent or non-covalent bond linkages, and can be divided into 1-D, 2-D, and 3-D polymer brushes, respectively, depending on the substrates. Different from the corresponding linear counterpart with similar molecular composition, 1-D polymer brush has some attractive properties including wormlike conformation, compact molecular dimension, and notable chain end effects due to its compact and densely grafted structure. The introduction of polymer chains onto the surface of a 2-D or 3-D matrix can not only improve surface-related properties of the matrix significantly, but also endow new functionalities with the obtained hybrid polymer brushes. Thus, polymer brush is of great interest in the fields of polymer and material science due to its potential applications in catalysis, nanolithography, biomineralization, drug delivery, medical diagnosis, optoelectronics, and so on. With the advent of living/controlled polymerization, organic, and supramolecular chemistry, a large number of 1-D, 2-D and 3-D polymer brushes have been prepared. However, the development of highly efficient synthetic protocols for the preparation of polymer brush with precisely controlled composition, structure, and functionality remains a key challenge. Herein, we summarize our recent efforts on the development of efficient methods to prepare 1-D, 2-D, and 3-D polymer brushes and the exploration of their potential applications in drug delivery, anti-fouling coating, catalysis, and lithium-ion battery.
Polymer brush generally refers to a kind of special macromolecular structures, of which polymer chains are densely tethered to another polymer chain (one-dimension, 1-D), the surface of a planar (two-dimension, 2-D), a spherical or a cylindrical (three-dimension, 3-D) solid matrice via stable covalent or non-covalent bond linkages, and can be divided into 1-D, 2-D, and 3-D polymer brushes, respectively, depending on the substrates. Different from the corresponding linear counterpart with similar molecular composition, 1-D polymer brush has some attractive properties including wormlike conformation, compact molecular dimension, and notable chain end effects due to its compact and densely grafted structure. The introduction of polymer chains onto the surface of a 2-D or 3-D matrix can not only improve surface-related properties of the matrix significantly, but also endow new functionalities with the obtained hybrid polymer brushes. Thus, polymer brush is of great interest in the fields of polymer and material science due to its potential applications in catalysis, nanolithography, biomineralization, drug delivery, medical diagnosis, optoelectronics, and so on. With the advent of living/controlled polymerization, organic, and supramolecular chemistry, a large number of 1-D, 2-D and 3-D polymer brushes have been prepared. However, the development of highly efficient synthetic protocols for the preparation of polymer brush with precisely controlled composition, structure, and functionality remains a key challenge. Herein, we summarize our recent efforts on the development of efficient methods to prepare 1-D, 2-D, and 3-D polymer brushes and the exploration of their potential applications in drug delivery, anti-fouling coating, catalysis, and lithium-ion battery.
2018, 0(12): 1482-1492
doi: 10.11777/j.issn1000-3304.2018.18165
Abstract:
As a class of typical organic/inorganic polymers, polysiloxanes are widely used in numerous areas owing to their remarkable properties, such as excellent environmental adaptability and endurance of wide temperature range. A broad spectrum of applications has been exploited for polysiloxanes, including surfactants, lubricants, adhesives, and insulating or coating materials. The overall properties of polysiloxanes are dependent primarily on its backbone. For example, poly(dimethylsiloxane) (PDMS), as a typical representative for polysiloxanes, shows special characteristics such as a low glass transition temperature, thermal stability, antioxidant stability, and physiological inertness. Anionic ring-opening polymerization of cyclosiloxanes is a prevalent approach to preparing polysiloxanes with various chain structures and functionalities and one of the most important areas for organosilicone research. Generally, the reaction processes of anionic ring-opening polymerizations are controllable in terms of a specific molecular weight, narrow molecular weight distributions, and well-defined structures. Besides, anionic ring-opening polymerization of cyclosiloxanes can be very useful in the preparation of new polymers with novel structures, particularly the microstructure-controlled copolymers that are difficult to be achieved by homopolymerization and conventional methods otherwise. Thus, anionic ring-opening polymerizations of cyclosiloxanes have received wide attention in the past decades. Focusing on cyclosiloxanes with different chemical structures used in anionic ring-opening polymerizations, this review elucidates the corresponding initiating agents, polymerization conditions, and final products involved in both homopolymerization and copolymerization processes. The covered topics regarding various monomers and initiating agents toward anionic ring-opening polymerizations of cyclosiloxanes will be of particular interest to organosilicon chemists as well as polymer and catalytic scientists who concern the precise control of the linear, branched, and cross-linked structure of polysiloxanes. These would be essential for preparing the next generation of organosilicon materials with much superior properties. A great number of research groups both domestic and overseas have polymerized various cyclic compounds by using different formulas, and the representative polymerization systems have been set out for convenient retrieval and comparison.
As a class of typical organic/inorganic polymers, polysiloxanes are widely used in numerous areas owing to their remarkable properties, such as excellent environmental adaptability and endurance of wide temperature range. A broad spectrum of applications has been exploited for polysiloxanes, including surfactants, lubricants, adhesives, and insulating or coating materials. The overall properties of polysiloxanes are dependent primarily on its backbone. For example, poly(dimethylsiloxane) (PDMS), as a typical representative for polysiloxanes, shows special characteristics such as a low glass transition temperature, thermal stability, antioxidant stability, and physiological inertness. Anionic ring-opening polymerization of cyclosiloxanes is a prevalent approach to preparing polysiloxanes with various chain structures and functionalities and one of the most important areas for organosilicone research. Generally, the reaction processes of anionic ring-opening polymerizations are controllable in terms of a specific molecular weight, narrow molecular weight distributions, and well-defined structures. Besides, anionic ring-opening polymerization of cyclosiloxanes can be very useful in the preparation of new polymers with novel structures, particularly the microstructure-controlled copolymers that are difficult to be achieved by homopolymerization and conventional methods otherwise. Thus, anionic ring-opening polymerizations of cyclosiloxanes have received wide attention in the past decades. Focusing on cyclosiloxanes with different chemical structures used in anionic ring-opening polymerizations, this review elucidates the corresponding initiating agents, polymerization conditions, and final products involved in both homopolymerization and copolymerization processes. The covered topics regarding various monomers and initiating agents toward anionic ring-opening polymerizations of cyclosiloxanes will be of particular interest to organosilicon chemists as well as polymer and catalytic scientists who concern the precise control of the linear, branched, and cross-linked structure of polysiloxanes. These would be essential for preparing the next generation of organosilicon materials with much superior properties. A great number of research groups both domestic and overseas have polymerized various cyclic compounds by using different formulas, and the representative polymerization systems have been set out for convenient retrieval and comparison.
2018, 0(12): 1493-1506
doi: 10.11777/j.issn1000-3304.2018.18172
Abstract:
Nonlinear rheology for polymers is the foundational science underlying high efficiency and energy-saving processing of polymeric materials. For chainlike polymers, complicated interchain interactions affect their dynamics and determine the structure-processing-property relationship. This interaction is often called the entanglement, and becomes the key issue in polymer rheology. To our knowledge, the rheological behavior of entangled polymers is based on the de Gennes-Doi-Edwards tube model (DE theory), which reduces the many-chain interaction into a smooth confining tube and assumes the test chain undergoes the Rouse dynamics inside the tube. Some predictions based on the DE theory are in agreement with rheological results, for instance, the time-strain separated form of the reduced relaxation modulus. To overcome some obvious disadvantages and provide reasonable results, many improvements and refinements have also been made to the DE theory. However, the tube model is only an essential single-chain mean-field theory since its intuitive molecular picture is too simple the theory cannot be derived from first principles and lacks self-consistency. In brief, the tube model does not describe how entanglement arises and cannot address the problem of when, how, and why disentanglement occurs after the external deformation. The model is inadequate in describing the chain conformation under fast and large deformations, and fails to explain a number of experimental observations in recent studies, such as the shear banding and the nonquiescent relaxation which show remarkable strain localization phenomena. Therefore, it is necessary to reexamine the single-chain mean-field assumptions and to consider the many-chain interactions explicitly. In other words, the chain entanglement may involve active localized intermolecular interactions that should be preceived as network junctions, and the critical picture of barrier-free Rouse retraction is questionable. In this article, we provide a general introduction to the original tube model and its subsequent improvements, with an emphasis on the development, basic assumptions, and key concepts. We provide derivation of some key results and explain the physical meaning of the parameters. The article ends with an outlook of the challenges and opportunities in the theory for polymer rheology, hoping to motivate researchers to working on this field.
Nonlinear rheology for polymers is the foundational science underlying high efficiency and energy-saving processing of polymeric materials. For chainlike polymers, complicated interchain interactions affect their dynamics and determine the structure-processing-property relationship. This interaction is often called the entanglement, and becomes the key issue in polymer rheology. To our knowledge, the rheological behavior of entangled polymers is based on the de Gennes-Doi-Edwards tube model (DE theory), which reduces the many-chain interaction into a smooth confining tube and assumes the test chain undergoes the Rouse dynamics inside the tube. Some predictions based on the DE theory are in agreement with rheological results, for instance, the time-strain separated form of the reduced relaxation modulus. To overcome some obvious disadvantages and provide reasonable results, many improvements and refinements have also been made to the DE theory. However, the tube model is only an essential single-chain mean-field theory since its intuitive molecular picture is too simple the theory cannot be derived from first principles and lacks self-consistency. In brief, the tube model does not describe how entanglement arises and cannot address the problem of when, how, and why disentanglement occurs after the external deformation. The model is inadequate in describing the chain conformation under fast and large deformations, and fails to explain a number of experimental observations in recent studies, such as the shear banding and the nonquiescent relaxation which show remarkable strain localization phenomena. Therefore, it is necessary to reexamine the single-chain mean-field assumptions and to consider the many-chain interactions explicitly. In other words, the chain entanglement may involve active localized intermolecular interactions that should be preceived as network junctions, and the critical picture of barrier-free Rouse retraction is questionable. In this article, we provide a general introduction to the original tube model and its subsequent improvements, with an emphasis on the development, basic assumptions, and key concepts. We provide derivation of some key results and explain the physical meaning of the parameters. The article ends with an outlook of the challenges and opportunities in the theory for polymer rheology, hoping to motivate researchers to working on this field.
2018, 0(12): 1507-1513
doi: 10.11777/j.issn1000-3304.2018.18104
Abstract:
It is still a challenge to prepare single-layered or few-layered organic-silica hybrid nanomaterials now. In this study, we designed and synthesized an amphiphilic organosilane (PABI) with phenyl urea and carboxyl groups, and investigated its two-dimensional self-assembly and polymerization. The spontaneous formation of few-layered organic-silica hybrid nanomaterials was driven by synergetic association of the hydrophobic interactions, π-π stacking interactions, hydrogen-bond interactions, electrostatic repulsion and hydrolytic condensation of the precursor under the appropriate conditions. The results indicated that the two-dimensional self-assembly and the polymerization were related to the experimental conditions, such as the medium, the type and the content of the base. The structure of the hybrid nanomaterials was demonstrated by nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR) and 29Si cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS 29Si-NMR). The morphology of the hybrid nanomaterials was confirmed by electron microscopy. Two or three layered organic-silica hybrid nanomaterials were obtained by two-dimensional self-assembly and polymerization of PABI in water when using 1,1,3,3-tetramethylguanidine (TMG) as a base under suitable condition (mole ratio of TMG to PABI was 1.1:1 or 1.5:1). The laminated sheet of the materials, with lateral size ranging from several hundred nanometers to several micrometers and thickness of 6 – 9 nm, was demonstrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). However, when the content of TMG (mole ratio of TMG to PABI was 2:1) was too high, irregular aggregates were formed. In addition, irregular hybrid materials were obtained when organic solvents, such as DMF, DMSO, THF and MeOH, were respectively added to water. Moreover, when trimethylamine (TEA) and sodium hydroxide (NaOH) were used as bases, thick laminated sheets were obtained, and the result was consistent with X-ray diffraction spectrogram (XRD). These results are of great significance for preparation of few-layered or single-layered organic-silica hybrid nanomaterials.
It is still a challenge to prepare single-layered or few-layered organic-silica hybrid nanomaterials now. In this study, we designed and synthesized an amphiphilic organosilane (PABI) with phenyl urea and carboxyl groups, and investigated its two-dimensional self-assembly and polymerization. The spontaneous formation of few-layered organic-silica hybrid nanomaterials was driven by synergetic association of the hydrophobic interactions, π-π stacking interactions, hydrogen-bond interactions, electrostatic repulsion and hydrolytic condensation of the precursor under the appropriate conditions. The results indicated that the two-dimensional self-assembly and the polymerization were related to the experimental conditions, such as the medium, the type and the content of the base. The structure of the hybrid nanomaterials was demonstrated by nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FTIR) and 29Si cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS 29Si-NMR). The morphology of the hybrid nanomaterials was confirmed by electron microscopy. Two or three layered organic-silica hybrid nanomaterials were obtained by two-dimensional self-assembly and polymerization of PABI in water when using 1,1,3,3-tetramethylguanidine (TMG) as a base under suitable condition (mole ratio of TMG to PABI was 1.1:1 or 1.5:1). The laminated sheet of the materials, with lateral size ranging from several hundred nanometers to several micrometers and thickness of 6 – 9 nm, was demonstrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). However, when the content of TMG (mole ratio of TMG to PABI was 2:1) was too high, irregular aggregates were formed. In addition, irregular hybrid materials were obtained when organic solvents, such as DMF, DMSO, THF and MeOH, were respectively added to water. Moreover, when trimethylamine (TEA) and sodium hydroxide (NaOH) were used as bases, thick laminated sheets were obtained, and the result was consistent with X-ray diffraction spectrogram (XRD). These results are of great significance for preparation of few-layered or single-layered organic-silica hybrid nanomaterials.
2018, 0(12): 1514-1523
doi: 10.11777/j.issn1000-3304.2018.18133
Abstract:
Dynamic covalent polymers that inherit the reversibility and robustness of dynamic covalent bonds have attracted considerable attention in terms of self-healing, stimuli-responsiveness, and recyclability. However, most of them require an external stimulus to induce their dynamic properties, which may limit their application. Here, two dynamic covalent polymers based on ditelluride bonds were prepared, which were free of external conditions. First, a novel stable ditelluride-containing compound, di-(1-hydroxypropyl) ditelluride ((HOC3H6Te)2) was synthesized. Then, two ditelluride-containing polymers, polycaprolactone (PCLTe)2 and poly(1,3-trimethylene carbonate) (PTMCTe)2 were synthesized via the enzymatic ring-opening polymerization using (HOC3H6Te)2 as the initiator and Novozym 435 as the catalyst. The structures of (PCLTe)2 and (PTMCTe)2 were verified by 1H-NMR and 125Te-NMR. The dynamic properties of the ditelluride-containing polymers were investigated using (PCLTe)2 and (PTMCTe)2 as the model polymers and confirmed by 1H-NMR, 13C-NMR and 125Te-NMR spectra. The results indicated that the ditelluride exchange between (PCLTe)2 and diphenyl ditelluride ((PhTe)2) could occur spontaneously in the dark at room temperature without any external stimuli and the equilibrium of the reaction could be reached immediately. The dynamic exchange between (PCLTe)2 and (PTMCTe)2 was confirmed by 125Te-NMR spectrum and MALDI-TOF mass, which could occur spontaneously without any external stimuli. The results of MALDI-TOF mass showed that a di-block polymer (PTMCTeTePCL) was formed during the exchange process. The tensile test results indicated that the tensile strength and the elongation of PCL/PTMC composite were 3.07 MPa and 38.26%, respectively. However, as for (PCLTe)2/(PTMCTe)2 composite, the tensile strength and the elongation were increased to 5.22 MPa and 80.51%, respectively. The scanning electron microscopy images showed that the compatibility between (PCLTe)2 and (PTMCTe)2 was significantly improved comparing with the PCL/PTMC composite. The results indicated that the ditelluride exchange had a great effect on the properties of (PCLTe)2/(PTMCTe)2 composite. This study developed the ditelluride-related dynamic chemistry and promoted the application of dynamic covalent polymers.
Dynamic covalent polymers that inherit the reversibility and robustness of dynamic covalent bonds have attracted considerable attention in terms of self-healing, stimuli-responsiveness, and recyclability. However, most of them require an external stimulus to induce their dynamic properties, which may limit their application. Here, two dynamic covalent polymers based on ditelluride bonds were prepared, which were free of external conditions. First, a novel stable ditelluride-containing compound, di-(1-hydroxypropyl) ditelluride ((HOC3H6Te)2) was synthesized. Then, two ditelluride-containing polymers, polycaprolactone (PCLTe)2 and poly(1,3-trimethylene carbonate) (PTMCTe)2 were synthesized via the enzymatic ring-opening polymerization using (HOC3H6Te)2 as the initiator and Novozym 435 as the catalyst. The structures of (PCLTe)2 and (PTMCTe)2 were verified by 1H-NMR and 125Te-NMR. The dynamic properties of the ditelluride-containing polymers were investigated using (PCLTe)2 and (PTMCTe)2 as the model polymers and confirmed by 1H-NMR, 13C-NMR and 125Te-NMR spectra. The results indicated that the ditelluride exchange between (PCLTe)2 and diphenyl ditelluride ((PhTe)2) could occur spontaneously in the dark at room temperature without any external stimuli and the equilibrium of the reaction could be reached immediately. The dynamic exchange between (PCLTe)2 and (PTMCTe)2 was confirmed by 125Te-NMR spectrum and MALDI-TOF mass, which could occur spontaneously without any external stimuli. The results of MALDI-TOF mass showed that a di-block polymer (PTMCTeTePCL) was formed during the exchange process. The tensile test results indicated that the tensile strength and the elongation of PCL/PTMC composite were 3.07 MPa and 38.26%, respectively. However, as for (PCLTe)2/(PTMCTe)2 composite, the tensile strength and the elongation were increased to 5.22 MPa and 80.51%, respectively. The scanning electron microscopy images showed that the compatibility between (PCLTe)2 and (PTMCTe)2 was significantly improved comparing with the PCL/PTMC composite. The results indicated that the ditelluride exchange had a great effect on the properties of (PCLTe)2/(PTMCTe)2 composite. This study developed the ditelluride-related dynamic chemistry and promoted the application of dynamic covalent polymers.
2018, 0(12): 1524-1531
doi: 10.11777/j.issn1000-3304.2018.18109
Abstract:
Composite nanofiltration membranes with tunable permeation and separation properties were prepared by interfacial crosslinking reaction between polydopamine (PDA) and trimesoyl chloride (TMC). Dopamine was first allowed to self-polymerize into oligomers or nanoaggregates in its aqueous solution at room temperature. As the size of PDA aggregates was readily modulated by measuring the pH of water phase, the separation precision of composite membranes could then be controlled. Ultraviolet spectra and dynamic light scattering ensured that the size of PDA nanoaggregates varied with pH values of aqueous solution. Attenuated total reflectance Fourier transform infrared spectroscopy, scanning electronic microscopy and contact angle measurement were employed to characterize the surface chemistry and morphology of the obtained composite membranes. It was found that, when the pH value of aqeuous phase increased from 6 to 12, the separation scale of composite membranes became progressively smaller and reached its highest selectivity at pH = 12, with rejection of Na2SO4 and sunset yellow being 90% and 97% respectively, flux reaching 64 L m−2 h−1 under 0.4 MPa. Increasing pH value to 13 caused a decline of separation properties, probably owing to a decomposition of PDA aggregates under strongly alkaline condition. Compared with PDA deposition method, which had been reported before, this work has considerably reduced the deposition time and produced a denser top layer, improving both preparation and separation efficiencies. By adjusting the size of the reactants before interfacial crosslinking, this study facilitated the regulation of separation precision of nanofiltration membranes.
Composite nanofiltration membranes with tunable permeation and separation properties were prepared by interfacial crosslinking reaction between polydopamine (PDA) and trimesoyl chloride (TMC). Dopamine was first allowed to self-polymerize into oligomers or nanoaggregates in its aqueous solution at room temperature. As the size of PDA aggregates was readily modulated by measuring the pH of water phase, the separation precision of composite membranes could then be controlled. Ultraviolet spectra and dynamic light scattering ensured that the size of PDA nanoaggregates varied with pH values of aqueous solution. Attenuated total reflectance Fourier transform infrared spectroscopy, scanning electronic microscopy and contact angle measurement were employed to characterize the surface chemistry and morphology of the obtained composite membranes. It was found that, when the pH value of aqeuous phase increased from 6 to 12, the separation scale of composite membranes became progressively smaller and reached its highest selectivity at pH = 12, with rejection of Na2SO4 and sunset yellow being 90% and 97% respectively, flux reaching 64 L m−2 h−1 under 0.4 MPa. Increasing pH value to 13 caused a decline of separation properties, probably owing to a decomposition of PDA aggregates under strongly alkaline condition. Compared with PDA deposition method, which had been reported before, this work has considerably reduced the deposition time and produced a denser top layer, improving both preparation and separation efficiencies. By adjusting the size of the reactants before interfacial crosslinking, this study facilitated the regulation of separation precision of nanofiltration membranes.
2018, 0(12): 1532-1538
doi: 10.11777/j.issn1000-3304.2018.18117
Abstract:
Electrospun nanofiber membrane of polyacrylonitrile (PAN ENMs) was chemically modified by reacting with ethylenediamine to make it into amino-functionalized on its surface, denoted as PAEA ENMs. The effects of ethylenediamine concentration, reaction temperature and reaction time of the hydrothermal process on the conversion of the cyano group and the adsorption capacity of the resulted nanofiber membranes were studied systematically. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and water contact angle test were used to characterize the physicochemical properties of PAEA ENMs. The results showed that PAEA nanofibers swelled and bended to a certain degree after hydrothermal treatment at 95 °C for 2 h, and the net-like structure of the membrane was well maintained. On the FTIR spectra, the peaks around 3300 - 3500 cm−1 were ascribed to the typical absorption of ―NH2 group. Water contact angle decreased from 114.5° for PAN ENMs to 44.7° for PAEA ENMs. All these suggest that PAEA ENMs was fabricated successfully. In order to investigate the netal ions removal performance through adsorption on the PAEA ENMs, a variety of Cr(VI) adsorption experiments were carried out and the adsorption kinetics and adsorption isotherms analized. The results showed that the adsorption capacity of PAEA ENMs was as high as 175.94 mg/g at pH = 2, and the adsorption equilibrium can be reached within 8 h. This is mainly due to the protonation of ―NH2 groups under the acid condition, which is benefit for adsorbing negative HCrO4–. The adsorption behavior fitted to the pesudo-second order kinetics and Langmuir isotherm adsorption model. Moreover, the PAEA ENMs can be reused after being washed with dilute NaOH solution separated from water. About 70% of its initial adsorption capacity was retained after four recycled use. Therefore, this PAEA ENMs has a high recyclability and is promising material for heavy metal ions adsorption.
Electrospun nanofiber membrane of polyacrylonitrile (PAN ENMs) was chemically modified by reacting with ethylenediamine to make it into amino-functionalized on its surface, denoted as PAEA ENMs. The effects of ethylenediamine concentration, reaction temperature and reaction time of the hydrothermal process on the conversion of the cyano group and the adsorption capacity of the resulted nanofiber membranes were studied systematically. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and water contact angle test were used to characterize the physicochemical properties of PAEA ENMs. The results showed that PAEA nanofibers swelled and bended to a certain degree after hydrothermal treatment at 95 °C for 2 h, and the net-like structure of the membrane was well maintained. On the FTIR spectra, the peaks around 3300 - 3500 cm−1 were ascribed to the typical absorption of ―NH2 group. Water contact angle decreased from 114.5° for PAN ENMs to 44.7° for PAEA ENMs. All these suggest that PAEA ENMs was fabricated successfully. In order to investigate the netal ions removal performance through adsorption on the PAEA ENMs, a variety of Cr(VI) adsorption experiments were carried out and the adsorption kinetics and adsorption isotherms analized. The results showed that the adsorption capacity of PAEA ENMs was as high as 175.94 mg/g at pH = 2, and the adsorption equilibrium can be reached within 8 h. This is mainly due to the protonation of ―NH2 groups under the acid condition, which is benefit for adsorbing negative HCrO4–. The adsorption behavior fitted to the pesudo-second order kinetics and Langmuir isotherm adsorption model. Moreover, the PAEA ENMs can be reused after being washed with dilute NaOH solution separated from water. About 70% of its initial adsorption capacity was retained after four recycled use. Therefore, this PAEA ENMs has a high recyclability and is promising material for heavy metal ions adsorption.
2018, 0(12): 1539-1547
doi: 10.11777/j.issn1000-3304.2018.18090
Abstract:
The copolymers of propylene/11-iodo-1-undecene were taken as intermediates and the iodine group underwent a nucleophilic substitution reaction or click reaction with N-methylimidazole or 2-mercaptonoaniline to prepare isotactic polypropylene ionomers. Isotactic polypropylene (iPP) and bio-renewable polyamide 11 (PA11) were mixed with the isotactic polypropylene ionomers to prepare novel polymer blends with excellent physical properties. The miscibility, morphology and mechanical properties of iPP/ionomer blends, PA11/ionomer blends and iPP/PA11/ionomer blends were investigated, respectively. DMA analysis revealed that miscibility of iPP and PA11 was improved by addition of the isotactic polypropylene ionomers, which served as an effective compatibilizer and played a key role in improving toughness of iPP/PA11 blends. As observed, particles size of the dispersed phase (PA11) was significantly reduced from about 20 μm to 1 μm in the ternary blends of iPP/PA11/ionomer. Interface between the matrix and the dispersed phase became blurred and the gap disappeared in the ternary blend of iPP/PA11/ionomer (70/30/5), as observed on the SEM images of the cryo-fractured surface of the blend. Accordingly, notched impact strength of the same ternary blend was greatly improved from 2.11 kJ/m2 to 6.73 kJ/m2 without significantly sacrificing the tensile strength. To further study the toughening effect of iPP/PA11/ionomer ternary blends, the fracture surface of the impact specimen was also investigated. As proved, the iPP/PA11 (70/30) blend showed a smooth and featureless fracture surface without evident deformation, indicating a typical brittle fracture behavior, while the fracture surfaces of the ternary blends was increasingly rough and many irregularities were clearly observed, indicating a ductile fracture behavior. Here we proved that the synthesized isotactic polypropylene ionomers enhanced the two-phase interface interaction and the compatibility in the iPP/PA11/ionomer ternary blend. It is therefore a very promising and effective compatibilizer for iPP/PA11 blends. Moreover, the resulting iPP/PA11 blends with excellent impact properties and tensile properties are very promising in practically application.
The copolymers of propylene/11-iodo-1-undecene were taken as intermediates and the iodine group underwent a nucleophilic substitution reaction or click reaction with N-methylimidazole or 2-mercaptonoaniline to prepare isotactic polypropylene ionomers. Isotactic polypropylene (iPP) and bio-renewable polyamide 11 (PA11) were mixed with the isotactic polypropylene ionomers to prepare novel polymer blends with excellent physical properties. The miscibility, morphology and mechanical properties of iPP/ionomer blends, PA11/ionomer blends and iPP/PA11/ionomer blends were investigated, respectively. DMA analysis revealed that miscibility of iPP and PA11 was improved by addition of the isotactic polypropylene ionomers, which served as an effective compatibilizer and played a key role in improving toughness of iPP/PA11 blends. As observed, particles size of the dispersed phase (PA11) was significantly reduced from about 20 μm to 1 μm in the ternary blends of iPP/PA11/ionomer. Interface between the matrix and the dispersed phase became blurred and the gap disappeared in the ternary blend of iPP/PA11/ionomer (70/30/5), as observed on the SEM images of the cryo-fractured surface of the blend. Accordingly, notched impact strength of the same ternary blend was greatly improved from 2.11 kJ/m2 to 6.73 kJ/m2 without significantly sacrificing the tensile strength. To further study the toughening effect of iPP/PA11/ionomer ternary blends, the fracture surface of the impact specimen was also investigated. As proved, the iPP/PA11 (70/30) blend showed a smooth and featureless fracture surface without evident deformation, indicating a typical brittle fracture behavior, while the fracture surfaces of the ternary blends was increasingly rough and many irregularities were clearly observed, indicating a ductile fracture behavior. Here we proved that the synthesized isotactic polypropylene ionomers enhanced the two-phase interface interaction and the compatibility in the iPP/PA11/ionomer ternary blend. It is therefore a very promising and effective compatibilizer for iPP/PA11 blends. Moreover, the resulting iPP/PA11 blends with excellent impact properties and tensile properties are very promising in practically application.
2018, 0(12): 1548-1557
doi: 10.11777/j.issn1000-3304.2018.18097
Abstract:
Understanding the defect removal process is crucial for the fabrication of defect-free self-assembled structures in block copolymer thin films. In this study, the removal of the dislocation dipole defect in thin films of perpendicular lamellar block copolymers on substrates modified by grafting polymers has been extensively studied. As revealed in previous studies, the " bridge” structure, which converts the slow hopping diffusion of block copolymer chains to fast interfacial diffusion, is a key factor to understand the mechanism of the defect removal process. Polymer grafting onto substrates is a widely accepted way to control domain orientation and fabricate surface pattern for directed self-assembly (DSA). However, the role of the grafted polymers on defect removal is unclear. In this study, the string method coupled with the self-consistent field theory (SCFT) is used to explore the influence of grafted polymers on the removal of a dislocation dipole in lamellar-froming thin films assembled by symmetric AB diblock copoymers. It is found that the " immersion effect” and the " rearrangement effect” introduced by the grafted polymers can facilitate the hopping diffusion of the block copolymer chains through reducing the effective χAB, thus making the formation of the bridge structure easier. The decrease of the softness of the brush layer (γ) will enhance these two effects and reduce the energy barrier of the transition state of the defect removal process. In the limit of γ = 0, the bridge structure is found to already exist in the dislocation dipole near the brush layer, leading to a diminishing energy barrier of the removal process. Using the symmetric PS-b-PMMA with a number-average molecular weight of ≈ 5.1 × 104 at 195 °C as an example, we estimated the annealing time required to eliminate the dislocation dipole by assuming the diffusion coefficient of the hopping diffusion of block copolymers being D⊥ ≈ 10−13 cm2/s. The annealing time are estimated to be τ = 91.4 s and 150.9 s for extremely soft confinement (γ = 0) and intermediate soft confinement (γ = 30), respectively. During the defect removal process, the brush layer will redistribute its density along the normal and the lateral directions of the substrate in response to the structural evolution of the thin film due to the " rearrangement effect”. Thus, the morphology of the brush layer reflects the microstructure of the thin film near the bottom substrate.
Understanding the defect removal process is crucial for the fabrication of defect-free self-assembled structures in block copolymer thin films. In this study, the removal of the dislocation dipole defect in thin films of perpendicular lamellar block copolymers on substrates modified by grafting polymers has been extensively studied. As revealed in previous studies, the " bridge” structure, which converts the slow hopping diffusion of block copolymer chains to fast interfacial diffusion, is a key factor to understand the mechanism of the defect removal process. Polymer grafting onto substrates is a widely accepted way to control domain orientation and fabricate surface pattern for directed self-assembly (DSA). However, the role of the grafted polymers on defect removal is unclear. In this study, the string method coupled with the self-consistent field theory (SCFT) is used to explore the influence of grafted polymers on the removal of a dislocation dipole in lamellar-froming thin films assembled by symmetric AB diblock copoymers. It is found that the " immersion effect” and the " rearrangement effect” introduced by the grafted polymers can facilitate the hopping diffusion of the block copolymer chains through reducing the effective χAB, thus making the formation of the bridge structure easier. The decrease of the softness of the brush layer (γ) will enhance these two effects and reduce the energy barrier of the transition state of the defect removal process. In the limit of γ = 0, the bridge structure is found to already exist in the dislocation dipole near the brush layer, leading to a diminishing energy barrier of the removal process. Using the symmetric PS-b-PMMA with a number-average molecular weight of ≈ 5.1 × 104 at 195 °C as an example, we estimated the annealing time required to eliminate the dislocation dipole by assuming the diffusion coefficient of the hopping diffusion of block copolymers being D⊥ ≈ 10−13 cm2/s. The annealing time are estimated to be τ = 91.4 s and 150.9 s for extremely soft confinement (γ = 0) and intermediate soft confinement (γ = 30), respectively. During the defect removal process, the brush layer will redistribute its density along the normal and the lateral directions of the substrate in response to the structural evolution of the thin film due to the " rearrangement effect”. Thus, the morphology of the brush layer reflects the microstructure of the thin film near the bottom substrate.
2018, 0(12): 1558-1562
doi: 10.11777/j.issn1000-3304.2018.18170
Abstract:
This article made a thorough analysis and assessment of the recently published book titled " Polymer Nonlinear Rheology: Macroscopic phenomenology and Molecular Foundation”. The author of the book used simple language, along with vivid graphical illustrations, rigorous logical and dialectical approaches and straightforward mathematical formulations, to describe the basic concepts and models for nonlinear polymer rheology. The book introduced many new concepts such as yielding, finite cohesion force, decohesion of the entanglement network through chain disentanglement. These ideas were applied to rationalize several leading phenomena such as stress overshoot, macroscopic movements after termination of external deformation, shear banding, " strain hardening” in melt stretching, etc. We recommend this book to young readers in our country who are interested in the frontier research topics in the field. Seasoned researcher working in polymer rheology should also find the book helpful, which allows them to come up with innovative research directions and elevates their own ability to carry out cut-edge activities.
This article made a thorough analysis and assessment of the recently published book titled " Polymer Nonlinear Rheology: Macroscopic phenomenology and Molecular Foundation”. The author of the book used simple language, along with vivid graphical illustrations, rigorous logical and dialectical approaches and straightforward mathematical formulations, to describe the basic concepts and models for nonlinear polymer rheology. The book introduced many new concepts such as yielding, finite cohesion force, decohesion of the entanglement network through chain disentanglement. These ideas were applied to rationalize several leading phenomena such as stress overshoot, macroscopic movements after termination of external deformation, shear banding, " strain hardening” in melt stretching, etc. We recommend this book to young readers in our country who are interested in the frontier research topics in the field. Seasoned researcher working in polymer rheology should also find the book helpful, which allows them to come up with innovative research directions and elevates their own ability to carry out cut-edge activities.
